Ofloxacin

What it is

Ofloxacin is a synthetic fluoroquinolone antibacterial, taken by mouth as 200, 300 or 400 mg film-coated tablets and also sold as eye drops and ear drops. Oral bioavailability is about 98%, peak blood levels occur one to two hours after a dose, and it is cleared mainly by the kidneys. Levofloxacin, a separate widely used antibiotic, is the purified active half of the same molecule. This write-up covers the oral tablet.

What the research says

Ofloxacin clears common bacterial infections: in a 688-patient randomised trial in women with uncomplicated cystitis a 3-day course eradicated the organism in 97% and achieved clinical success in 96%, statistically similar to ciprofloxacin and co-trimoxazole, and in pelvic inflammatory disease a 10-day course matched cefoxitin plus doxycycline (95% versus 93% cure or improvement). Against that sits a boxed warning for disabling and potentially irreversible tendon, nerve and central nervous system reactions and for worsening myasthenia gravis, and the regulator now tells prescribers to reserve the drug for people with no alternative for bronchitis and for simple cystitis. The quantified harms are mostly in the class rather than the molecule: Achilles rupture odds of 28.4 for current ofloxacin exposure in people over 60 in one UK case-control study, tendon rupture at an extra 2.9 per 10,000 patients, peripheral neuropathy at an extra 2.4 per 10,000 patient-years. Resistance has also overtaken two uses: fluoroquinolones are no longer recommended for gonorrhoea, and ofloxacin was beaten by azithromycin in resistant enteric fever.

Evidence grade: Well established.

How it works

Drug class: Fluoroquinolone (quinolone) antibacterial

Ofloxacin kills bacteria by jamming two bacterial enzymes, DNA gyrase and topoisomerase IV, that untangle and re-join DNA. Without them the bacterium cannot copy, read or repair its own DNA, so it dies. Human cells do not use these bacterial enzymes, which is why the drug is selective for bacteria; its chemistry is unrelated to penicillins, macrolides and aminoglycosides, so it can work where those fail. (Source 1)

Boxed warning

WARNING SERIOUS ADVERSE REACTIONS INCLUDING TENDINITIS, TENDON RUPTURE, PERIPHERAL NEUROPATHY, CENTRAL NERVOUS SYSTEM EFFECTS AND EXACERBATION OF MYASTHENIA GRAVIS Fluoroquinolones, including ofloxacin, have been associated with disabling and potentially irreversible serious adverse reactions that have occurred together, including: • Tendinitis and tendon rupture • Peripheral neuropathy • Central nervous system effects (see WARNINGS). Discontinue ofloxacin immediately and avoid the use of fluoroquinolones, including ofloxacin, in patients who experience any of these serious adverse reactions (see WARNINGS). • Fluoroquinolones, including ofloxacin, may exacerbate muscle weakness in persons with myasthenia gravis. Avoid ofloxacin in patients with a known history of myasthenia gravis (See WARNINGS). •Because fluoroquinolones, including ofloxacin, have been associated with serious adverse reactions (see WARNINGS), reserve ofloxacin for use in patients who have no alternative treatment options for the following indications: o Acute exacerbation of chronic bronchitis o Uncomplicated cystitis (see INDICATIONS and USAGE)

(Source 2)

What it is used for

• A randomised double-blind trial in 688 evaluable women found a 3-day course of ofloxacin 200 mg twice daily eradicated the pathogen in 97% and gave 96% clinical success, similar to ciprofloxacin and co-trimoxazole. The label now tells prescribers to reserve ofloxacin for this use for patients with no alternative, because many simple bladder infections settle on their own and the class carries disabling harms. Evidence: established. (Source 3)
• Randomised trials support the regimen: 95% cure or improvement versus 93% for cefoxitin plus doxycycline in 1993, and in a 2021 trial ofloxacin plus metronidazole as standard of care was not matched by a short azithromycin-based regimen. But CDC withdrew fluoroquinolones for gonococcal infection and associated conditions including PID in 2007 because of resistance, so the label indication and the practice guideline now conflict. Evidence: disputed. (Source 4)
• The approved label still lists gonorrhoea, but CDC stopped recommending fluoroquinolones for gonococcal infections in 2007 on the basis of rising resistance in national surveillance, leaving cephalosporins as the only recommended class. The label is a position with a date, and on this use it has been overtaken by resistance data. Evidence: not-supported. (Source 5)
• These are label indications with the label's own qualifier that ofloxacin treats mild to moderate infections caused by susceptible organisms. For bronchitis the label now adds that because the illness is often self-limiting and the class causes serious reactions, ofloxacin should be reserved for patients with no alternative treatment options. Evidence: limited. (Source 6)
• A Cochrane review of 26 trials in 3033 patients found fluoroquinolones generally performed well and in one Pakistani study ofloxacin was superior to chloramphenicol and co-trimoxazole, but in Vietnamese populations with multi-drug and nalidixic-acid resistance a 7-day ofloxacin course failed more often than azithromycin (RR 2.20). The review declined to draw firm general conclusions because resistance shifts over time. Evidence: disputed. (Source 7)
• A Cochrane review of five randomised trials in 1330 participants concluded there is insufficient evidence to tell whether adding or substituting a fluoroquinolone, including ofloxacin in place of ethambutol, reduces death or relapse or speeds culture conversion. The evidence was graded very low to low quality. Evidence: unknown. (Source 8)

Interactions

• Iron (ferrous sulphate and other iron supplements) (pharmacokinetic study): Iron binds ofloxacin in the gut and less of the antibiotic reaches the bloodstream. In a crossover study in healthy volunteers, ferrous sulphate equal to 100 mg of elemental iron cut ofloxacin's total exposure by a quarter and its peak level by a third. Ofloxacin was the least affected of the three quinolones tested, but the authors still advised against taking the two together. (Source 9)
• Calcium carbonate antacids (and, by the label, calcium generally) (pharmacokinetic study): The label tells people to keep calcium two hours either side of a dose. The actual pharmacokinetic study is more specific: in 32 subjects, calcium carbonate had no significant effect on ofloxacin absorption at any of the tested separations, and the investigators concluded neither antacid interfered clinically provided at least two hours separated them. Simultaneous dosing was never tested, so the two-hour rule is untested at zero separation rather than disproved. (Source 10)
• Magnesium and aluminium hydroxide antacids (pharmacokinetic study): In the same study, magnesium-aluminium hydroxide given two hours before ofloxacin produced a small but statistically significant drop in both total exposure and peak level, more than calcium carbonate did. (Source 10)
• Aluminium hydroxide specifically, with in-vitro evidence for iron and calcium (pharmacokinetic study): A volunteer study of six metal-containing medicines found only aluminium hydroxide lowered ofloxacin levels and slowed its absorption in the body. In simulated gastric fluid, however, ferrous sulphate, aluminium hydroxide and calcium carbonate all cut the amount of free ofloxacin to roughly two thirds to three quarters, by forming complexes with the metal ions. The in-vitro and in-vivo results did not agree for iron and calcium. Limit: The sentence immediately before this passage in the published abstract reads "were unaffected (P less than 0.05) by the metallic drugs". A p-value below 0.05 denotes a significant difference, so "unaffected" and the p-value contradict each other; it was almost certainly meant to read P greater than 0.05. Quoted as printed. (Source 11)
• Zinc-containing multivitamins, sucralfate, and didanosine buffered formulations (label): The label groups these with antacids and iron: all can substantially cut how much ofloxacin is absorbed, giving blood levels well below what is needed, and it directs that none be taken within two hours before or after a dose. For zinc specifically the evidence cited is the label's class statement rather than a published ofloxacin pharmacokinetic study. (Source 12)
• Milk and dairy (pharmacokinetic study): Unlike the tetracyclines, ofloxacin is not meaningfully blocked by milk. In a three-way crossover study in 21 volunteers, milk did not change the rate or the extent of absorption or the elimination of ofloxacin. (Source 13)
• Food in general (pharmacokinetic study): A meal slows the drug down without reducing how much gets in: peak concentration fell 20% and the time to peak was an hour later, while total absorption and half-life were unchanged. The investigators called the effect of food and milk clinically insignificant. (Source 13)
• Caffeine (label): Some quinolones slow caffeine clearance; ofloxacin appears not to. The label's position is that no interaction between ofloxacin and caffeine has been detected. (Source 12)
• Theophylline (label): Ofloxacin can raise theophylline blood levels and prolong its half-life, increasing the risk of theophylline toxicity including seizures, which can happen with or without a measured rise in the level. (Source 12)
• Warfarin (label): Some quinolones increase the anticoagulant effect of warfarin, so clotting tests should be watched closely if the two are combined. (Source 12)
• Non-steroidal anti-inflammatory drugs (ibuprofen, naproxen and similar) (label): Taking an NSAID with a quinolone may increase central nervous system stimulation and the risk of convulsive seizures. (Source 12)
• Insulin and oral diabetes medicines (label): Both high and low blood sugar have been reported when quinolones are taken with diabetes medicines, and severe hypoglycaemia with coma or death has been reported; glucose should be monitored closely. (Source 12)
• Alcohol (label): No alcohol interaction is documented for ofloxacin: the FDA label's drug interactions section does not list alcohol, and we found no pharmacokinetic study of the combination. What the label does record is that the drug causes dizziness, somnolence and sleep disorders in 1 to 3% of patients, effects alcohol would be expected to add to, so the absence of a listed interaction is an absence of study rather than evidence of safety. (Source 14)

Stopping it

• Ofloxacin is not a drug with dependence or withdrawal; stopping is event-driven. The boxed warning instructs immediate discontinuation and lifelong avoidance of the whole fluoroquinolone class in anyone who gets one of the serious reactions. (Source 2)
• For tendon problems the trigger is any pain, swelling or inflammation of a tendon, and the warning adds that the drug should be avoided altogether in people with a history of tendon disorders. (Source 15)
• For nerve symptoms the aim of stopping promptly is explicitly to prevent permanent damage: the label says to discontinue immediately on pain, burning, tingling, numbness, weakness or altered sensation in order to minimise the development of an irreversible condition. (Source 15)
• Stopping an antibiotic course early has its own cost. The label's stewardship statement is that ofloxacin should be used only for infections proven or strongly suspected to be bacterial, to preserve the drug's effectiveness - the resistance story in gonorrhoea and enteric fever is what that is about. (Source 6)

What goes wrong

In clinical trials 11% of patients had a drug-related adverse reaction and 4% stopped the drug because of adverse experiences; nausea, headache and insomnia were the commonest events. (Source 14)

• Official position, Certainty not rated.
• Size: Phase 2 and 3 clinical trial programme; numbers not given in the label.
• Who: Patients receiving oral or intravenous ofloxacin.
• How long: Multiple-dose therapy.
• Result: Drug-related adverse reactions 11%; discontinuation 4%; most frequent events regardless of causality nausea 10%, headache 9%, insomnia 7%, external genital pruritus in women 6%, dizziness 5%, vaginitis 5%, diarrhoea 4%, vomiting 4%.
• Funding: Reported in the FDA-approved label; no placebo comparison is given, so these are not drug-versus-placebo differences.

The incidence of drug-related adverse reactions in patients during Phase 2 and 3 clinical trials was 11%. Among patients receiving multiple-dose therapy, 4% discontinued ofloxacin due to adverse experiences.In clinical trials, the following events were considered likely to be drug-related in patients receiving multiple doses of ofloxacin:nausea 3%, insomnia 3%, headache 1%, dizziness 1%, diarrhea 1%, vomiting 1%, rash 1%, pruritus 1%, external genital pruritus in women 1%, vaginitis 1%, dysgeusia 1%.In clinical trials, the most frequently reported adverse events, regardless of relationship to drug, were:nausea 10%, headache 9%, insomnia 7%, external genital pruritus in women 6%, dizziness 5%, vaginitis 5%, diarrhea 4%, vomiting 4%.

In a UK population case-control study, current ofloxacin exposure in people aged 60 and over carried the highest Achilles tendon rupture odds of any quinolone studied. (Source 16)

• Case-control study, Low certainty.
• Size: 1367 cases of first Achilles tendon rupture, 50,000 randomly sampled controls.
• Who: General Practice Research Database, United Kingdom, 1988-1998.
• How long: Current, recent and past exposure windows.
• Result: Adjusted OR for Achilles rupture with current quinolone exposure 4.3 (95% CI 2.4-7.8); in people 60 and over the OR for current ofloxacin exposure was 28.4 (95% CI 7.0-115.3) versus 3.6 for ciprofloxacin and 14.2 for norfloxacin; approximately 2% to 6% of all Achilles ruptures over 60 attributable to quinolones.
• Funding: not stated in the abstract; the ofloxacin-specific estimate rests on small numbers, reflected in the very wide confidence interval.

In persons aged 60 years and older, the OR was 28.4 (95% CI, 7.0-115.3) for current exposure to ofloxacin, while the ORs were 3.6 (95% CI, 1.4-9.1) and 14.2 (95% CI, 1.6-128.6) for ciprofloxacin and norfloxacin, respectively.

Fluoroquinolone exposure raised tendon rupture risk with an absolute excess of about 2.9 per 10,000 patients, rising sharply when an oral corticosteroid was taken at the same time. (Source 17)

• Case-control study, Low certainty.
• Size: Adults with tendon rupture matched to four controls each in The Health Improvement Network UK primary care database.
• Who: Adults prescribed a systemic fluoroquinolone or co-amoxiclav.
• How long: Risk persisted for 60 days after exposure.
• Result: Adjusted IRR 1.61 (95% CI 1.25-2.09) for any tendon rupture and 3.14 (2.11-4.65) for Achilles rupture; with oral corticosteroids 19.36 (7.78-48.19) for Achilles rupture; adjusted rate difference 2.9 and 2.1 per 10,000 patients, rising to 19.6 and 6.6 per 10,000 in people 60 and over on corticosteroids; no association with co-amoxiclav or statins.
• Funding: not stated in the abstract.

Limit of this finding: The abstract defines the measure as "adjusted rate difference (aRD)" and then prints it as "aDR"; that is a transposition in the published text, not a second measure. The 19.36 estimate for Achilles rupture with concomitant corticosteroids rests on few events, as its confidence interval of 7.78 to 48.19 shows.

The adjusted rate difference (aRD) with fluoroquinolone exposure was 2.9 and 2.1 per 10,000 patients for any and Achilles tendon rupture, respectively, and was greatest in people aged ≥ 60 years prescribed concomitant oral corticosteroid therapy (aDR 19.6 for any tendon and 6.6 Achilles tendon rupture per 10,000).

Current oral fluoroquinolone use was associated with about a 47% higher rate of new peripheral neuropathy, but the absolute risk was small: 2.4 cases per 10,000 patients per year of current use. (Source 18)

• Case-control study, Low certainty.
• Size: 5357 incident peripheral neuropathy cases matched to 17,285 controls, from a cohort of 1,338,900 adults.
• Who: UK primary care patients without diabetes prescribed a fluoroquinolone or amoxicillin-clavulanate, 1999-2015.
• How long: Risk persisted up to 180 days after exposure.
• Result: Adjusted incident rate ratio 1.47 (95% CI 1.13-1.92); risk rose about 3% per additional day of current exposure; absolute risk 2.4 (95% CI 1.8-3.1) per 10,000 patients per year of current use; number needed to harm for a 10-day course 152,083 (95% CI 117,742-202,778); no increased risk with amoxicillin-clavulanate.
• Funding: not stated in the abstract.

Limit of this finding: The paper's own sentence says the number needed to harm "was greatest among men and among patients older than 60 years". A greatest number needed to harm would mean the least harm, which is the opposite of the paper's point that risk was highest in those groups; the sentence is inverted as published. Do not read it as meaning men and older patients were least affected.

The absolute risk with current oral fluoroquinolone exposure was 2.4 (95% CI, 1.8-3.1) per 10 000 patients per year of current use. The number needed to harm for a 10-day course was 152 083 patients (95% CI, 117 742-202 778) and was greatest among men and among patients older than 60 years.

A separate US case-control study in middle-aged and older men found current fluoroquinolone users had about 83% higher odds of peripheral neuropathy, with no such signal for a control drug. (Source 19)

• Case-control study, Low certainty.
• Size: 6,226 cases and 24,904 matched controls.
• Who: US men aged 45 to 80 followed 2001-2011.
• How long: Current use.
• Result: Rate ratio 1.83 (95% CI 1.49-2.27) for current fluoroquinolone users and 2.07 (1.56-2.74) for current new users; finasteride, used as a negative control, gave 1.21 (0.97-1.51)
• Funding: not stated in the abstract.

Current users of FQs were at a higher risk of developing PN (RR = 1.83, 95% confidence interval [CI] 1.49-2.27). Current new users had the highest risk (RR = 2.07, 95% CI 1.56-2.74). No risk was observed for current users of finasteride (RR = 1.21, 95% CI 0.97-1.51).

Across 37 reported cases of fluoroquinolone-associated myasthenia gravis exacerbation, 30% needed ventilatory support and 5% died, with onset a median of one day after the dose; ofloxacin was the fluoroquinolone in two of the 27 FDA reports and in one of the ten published case reports. (Source 20)

• Case series, Very low certainty.
• Size: 37 unique cases (27 FDA adverse event reports and 10 published case reports)
• Who: Non-ventilated patients with known myasthenia gravis exposed to a systemic fluoroquinolone.
• How long: Median one day to exacerbation.
• Result: Dyspnoea in 19 (51%), myasthenic crisis requiring ventilation in 11 (30%), death in 2 (5%); generalised weakness 54%, dysphagia 24%; six patients (16%) had a positive rechallenge.
• Funding: US FDA authors; spontaneous reporting cannot give a rate or prove causation, though positive rechallenge in six cases strengthens the signal.

The 37 cases describe dyspnoea (n = 19; 51%), myasthenic crisis requiring ventilatory support (n = 11; 30%) and death (n = 2; 5%). Additional exacerbation-related adverse events were generalized muscle weakness (n = 20; 54%), dysphagia (n = 9; 24%), diplopia (n = 6; 16%) and ptosis (n = 6; 16%). Six patients (16%) experienced a positive rechallenge, with recurrent myasthenia gravis exacerbation after fluoroquinolone reintroduction.

A German nationwide claims cohort found fluoroquinolone users had about a 56% higher rate of aortic aneurysm or dissection than users of other antibiotics. (Source 21)

• Cohort study, Low certainty.
• Size: Statutory health insurance data covering about 87% of the German population, 2009-2017.
• Who: Patients treated with fluoroquinolones compared with a propensity-score-matched group on non-fluoroquinolone antibiotics.
• How long: 2009-2017.
• Result: Hazard ratio 1.56; 1.43 after excluding patients with pneumonia or aortic dissection; 1.48 adjusted for underlying infections, sex and age.
• Funding: not stated in the abstract; claims-based observational design with confounding by indication as the main competing explanation.

Limit of this finding: This abstract gives its three hazard ratios (1.56, 1.43 and 1.48) with no confidence intervals and no p-values anywhere, so how precise they are cannot be judged from the paper and the three cannot be compared with one another.

Patients treated with fluoroquinolones had a higher risk of developing AA/AAD compared to those treated with other antibiotics (HR: 1.56). In sensitivity analyses excluding patients with pneumonia or aortic dissection, the risk was slightly reduced (HR: 1.43). The HR remained elevated even when adjusted for underlying infections, sex and age (HR: 1.48), indicating a potential drug-related effect independent of specific infections.

Fluoroquinolones can disturb blood glucose, and severe hypoglycaemia leading to coma or death has been reported, mainly in people also taking diabetes medicines. (Source 22)

• Official position, Certainty not rated.
• Size: Not quantified; postmarketing reports.
• Who: Patients on fluoroquinolones, especially those also taking an oral hypoglycaemic agent or insulin.
• How long: Any.
• Result: No rate given; the label requires monitoring of blood glucose and immediate discontinuation if a hypoglycaemic reaction occurs.
• Funding: Regulatory position (FDA-approved label, DailyMed version published 23 June 2026)

Limit of this finding: The sentence "Ofloxacin has not been shown to be effective in the treatment of syphilis." sits in this label between the aortic-aneurysm paragraph and the blood-glucose paragraph, away from the gonorrhoea and syphilis paragraph it belongs with. That ordering is the label's own and has not been rearranged here.

Fluoroquinolones have been associated with disturbances of blood glucose, including symptomatic hyperglycemia and hypoglycemia, usually in diabetic patients receiving concomitant treatment with an oral hypoglycemic agent (e.g., glyburide) or with insulin. In these patients, careful monitoring of blood glucose is recommended. Severe cases of hypoglycemia resulting in coma or death have been reported.

Clostridioides difficile associated diarrhoea has been reported with ofloxacin and can range from mild diarrhoea to fatal colitis, including more than two months after the course. (Source 22)

• Official position, Certainty not rated.
• Size: Not quantified.
• Who: Anyone taking an antibacterial, ofloxacin included.
• How long: During or after treatment, reported over two months later.
• Result: No rate given; hypertoxin-producing strains cause increased morbidity and mortality and may require colectomy.
• Funding: Regulatory position (FDA-approved label)

Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including ofloxacin tablets, and may range in severity from mild diarrhea to fatal colitis.

The boxed warning states that the disabling tendon, nerve and central nervous system reactions can occur together in the same patient, within hours to weeks, in people of any age and with no pre-existing risk factors. (Source 15)

• Official position, Certainty not rated.
• Size: Not quantified.
• Who: Anyone taking a fluoroquinolone including ofloxacin.
• How long: Hours to weeks after starting; tendon problems reported up to several months after finishing.
• Result: No rates given; the label instructs immediate discontinuation at the first sign and avoidance of the whole class thereafter.
• Funding: Regulatory position (FDA-approved label)

Limit of this finding: Inside the peripheral-neuropathy paragraph this label prints "Symptoms may occur soon after initiation of norfloxacin". Norfloxacin is a different drug and the word appears nowhere else in the label; it is a copy-paste error in the FDA label itself, left as printed here. Read it as referring to ofloxacin.

These reactions can occur within hours to weeks after starting ofloxacin. Patients of any age or without pre-existing risk factors have experienced these adverse reactions (see Warnings)

What the evidence supports

A 3-day course of ofloxacin eradicated the causative organism in 97% of women with uncomplicated bladder infection, statistically similar to ciprofloxacin and co-trimoxazole. (Source 3)

• Randomized trial, Moderate certainty.
• Size: 866 enrolled, 688 (79%) evaluable; 231 on ofloxacin.
• Who: Women with acute, uncomplicated, symptomatic lower urinary tract infection; Escherichia coli in 81%.
• How long: 3 days of treatment, follow-up at 4 to 6 weeks.
• Result: Eradication 97% ofloxacin versus 94% ciprofloxacin and 93% co-trimoxazole; clinical success 96%, 93% and 95%; recurrence at 4-6 weeks 13%, 11% and 16%.
• Funding: not stated in the abstract; reported by the Ciprofloxacin Urinary Tract Infection Group, i.e. a comparator-sponsored trial group.

Eradication of the pretreatment pathogen at the end of therapy occurred in 94% of ciprofloxacin, 93% of trimethoprim/sulfamethoxazole, and 97% of ofloxacin-treated patients. At follow-up evaluation at 4 to 6 weeks, recurrence rates (relapse or reinfection) were 11% in the ciprofloxacin, 16% in the trimethoprim/sulfamethoxazole, and 13% in the ofloxacin treatment group. Clinical success at the end of therapy was 93% in the ciprofloxacin, 95% in the trimethoprim/sulfamethoxazole, and 96% in the ofloxacin treatment groups.

Oral ofloxacin matched intramuscular cefoxitin plus doxycycline for outpatient treatment of uncomplicated pelvic inflammatory disease, with fewer side effects. (Source 4)

• Randomized trial, Low certainty.
• Size: 268 women cultured; 128 and 121 evaluable in the two arms.
• Who: Outpatients with uncomplicated pelvic inflammatory disease; gonorrhoea in 16% and chlamydia in 12% at baseline.
• How long: 10 days.
• Result: Cure or improvement in 95% (122/128) on ofloxacin 400 mg twice daily versus 93% (112/121) on cefoxitin plus doxycycline; chlamydia eradication 100% versus 88%; side effects 7% versus 15%.
• Funding: not stated in the abstract; conducted by the Ambulatory PID Research Group.

Ninety-five percent (122/128) of the women treated with the ofloxacin regimen and 93% (112/121) of those treated with the cefoxitin/doxycycline regimen had cure or improvement on examination at a minimum of one follow-up visit.

In a 2021 randomised trial, a short azithromycin-based regimen could not be shown non-inferior to 14 days of ofloxacin plus metronidazole for mild-to-moderate pelvic inflammatory disease. (Source 23)

• Randomized trial, Low certainty.
• Size: 313 randomised (153 standard of care, 160 intervention); 227 in the per-protocol analysis.
• Who: Women with a clinical diagnosis of mild-to-moderate pelvic inflammatory disease at sexual health services.
• How long: 14 days standard of care versus 5 days azithromycin after ceftriaxone; outcome at day 14-21.
• Result: Clinical cure 72/153 (47.1%) standard of care versus 68/160 (42.5%) intervention in the randomised population; 67.3% versus 56.7% after exclusions, difference 10.6% (95% CI -23.2% to 1.9%); non-inferiority not demonstrated.
• Funding: not stated in the abstract; open-label for clinicians and participants with blinded outcome assessment; 86 of 313 women lost to follow-up or out of window.

Limit of this finding: The published abstract's point estimates and confidence intervals carry opposite signs: a difference in cure of 10.6% with an interval of -23.2% to 1.9% is arithmetically impossible, and the earlier interval "(95% CI -15.6% to 6.5%" is missing its closing bracket. The differences appear to be standard-of-care minus intervention while the intervals are the other way round. The direction of the trial result - non-inferiority not demonstrated - is not affected, but the signs cannot be read as printed.

Following exclusion of 86 women who were lost to follow-up, attended outside the day 14-21 follow-up period, or withdrew consent, 72/107 (67.3%) had clinical cure in the SoC arm compared with 68/120 (56.7%) in the IA, giving a difference in cure rate of 10.6% (95% CI -23.2% to 1.9%). We were unable to demonstrate non-inferiority of the IA compared with SoC arm.

What the evidence does not support

In resistant enteric fever in Vietnam, a seven-day ofloxacin course failed more than twice as often as azithromycin. (Source 7)

• Systematic review, Low certainty.
• Size: 213 participants across two trials within a review of 26 studies and 3033 patients.
• Who: Patients with culture-confirmed enteric fever carrying both multi-drug resistance and nalidixic acid resistance, Vietnam 1998-2002.
• How long: 7 days of each drug.
• Result: Higher rate of clinical failure with ofloxacin, RR 2.20 (95% CI 1.23 to 3.94)
• Funding: not stated in the abstract; Cochrane review, which notes many included studies were small.

Compared to a seven day course of azithromycin, a seven day course of ofloxacin had a higher rate of clinical failures in populations with both multi-drug resistance (MDR) and nalidixic acid resistance (NaR) enteric fever in Vietnam in 1998-2002 (two trials, 213 participants, RR 2.20, 95% CI 1.23 to 3.94).

For drug-sensitive tuberculosis, the trials of substituting a fluoroquinolone such as ofloxacin for ethambutol are too weak to show whether it helps or harms. (Source 8)

• Systematic review, Very low certainty.
• Size: Five RCTs, 1330 participants; three trials with 723 participants for the ethambutol substitution.
• Who: People with presumed drug-sensitive pulmonary tuberculosis on rifampicin and pyrazinamide-based regimens.
• How long: No included trial was shorter than six months.
• Result: For relapse, death, culture conversion at eight weeks and serious adverse events the review rates the evidence very low quality and states the effect is uncertain.
• Funding: not stated in the abstract; Cochrane review using GRADE.

There is insufficient evidence to be clear whether addition or substitution of fluoroquinolones for ethambutol or isoniazid in the first-line regimen reduces death or relapse, or increases culture conversion at eight weeks.

CDC withdrew fluoroquinolones, ofloxacin included, as a recommended treatment for gonorrhoea and associated conditions including pelvic inflammatory disease, because of rising resistance. (Source 5)

• Official position, Certainty not rated.
• Size: National Gonococcal Isolate Surveillance Project data; 339,593 reported US gonorrhoea cases in 2005.
• Who: People in the United States with gonococcal infection.
• How long: Policy change effective 2007, after staged regional withdrawals from 2000.
• Result: No effect size; the recommendation left cephalosporins as the only recommended and available class.
• Funding: US government agency position (CDC, 2007)

On the basis of the most recent evidence, CDC no longer recommends the use of fluoroquinolones for the treatment of gonococcal infections and associated conditions such as pelvic inflammatory disease (PID). Consequently, only one class of drugs, the cephalosporins, is still recommended and available for the treatment of gonorrhea.

A 2023 study that applied both a cohort and a case-crossover design across two large UK primary-care databases found no association between fluoroquinolone use and hospitalisation with aortic aneurysm or dissection once confounding was accounted for. (Source 24)

• Cohort study, Moderate certainty.
• Size: 3,586,207 adults in two UK databases plus 95,198 hospitalised cases in the case-crossover analysis.
• Who: Adults prescribed a systemic fluoroquinolone or a cephalosporin in UK primary care, 1997-2019.
• How long: Up to 22 years.
• Result: Crude pooled HR 1.28 (95% CI 1.13-1.44) but adjusted pooled HR 1.03 (0.91-1.17, P = .65); in the case-crossover analysis versus cephalosporin pooled OR 1.05 (0.87-1.27), versus trimethoprim 0.89 (0.75-1.06), versus co-amoxiclav 0.98 (0.82-1.18)
• Funding: not stated in the abstract.

In crude analyses, fluoroquinolone relative to cephalosporin use was associated with increased hospitalization with aortic aneurysm or dissection (pooled HR, 1.28; 95% CI, 1.13-1.44; P < .001) but after adjustment for potential confounders, this association disappeared (pooled adjusted HR, 1.03; 95% CI, 0.91-1.17; P = .65).

Where the research disagrees

Whether fluoroquinolones cause aortic aneurysm and dissection, which is in the ofloxacin label as a warning

• German nationwide statutory health insurance cohort, BMC Cardiovascular Disorders 2025, propensity-score-matched claims cohort: Fluoroquinolone use is associated with an increased risk of aortic aneurysm and dissection. These findings highlight the value of routine healthcare data in detecting adverse drug reactions and underline the need for careful risk–benefit evaluation when prescribing fluoroquinolones. (Source 25)
• Gopalakrishnan and colleagues, two UK databases with cohort and case-crossover designs, JAMA Cardiology 2023, cohort plus case-crossover with active comparators: When such confounding is accounted for, no association was evident, providing reassurance on the safety of fluoroquinolones with respect to aortic aneurysm or dissection. (Source 26)
• Korean nationwide study using a self-controlled case series and Cox models, European Heart Journal 2023, self-controlled case series and cohort in 954,308 patients: There was no significant difference in the risk of AA/AD in patients who were administered oral FQ compared to those administered 3GC. The study findings suggest that the use of FQ should not be deterred when clinically indicated. (Source 27)

Whether fluoroquinolones measurably worsen myasthenia gravis in practice

• Jones and colleagues, US FDA, review of adverse event reports and published cases, Drug Safety 2011, case-series from spontaneous reports plus literature review, with six positive rechallenges: Fluoroquinolone exposure may result in potentially life-threatening myasthenia gravis exacerbations in patients with underlying disease. (Source 28)
• Retrospective claims cohort of 1556 myasthenia gravis patients, Muscle and Nerve 2021, retrospective cohort with beta-lactam comparator; the authors note the confidence interval for fluoroquinolones was very wide (aOR 4.60, 0.55-38.57): Among 1556 MG patients receiving 894 fluoroquinolone prescriptions, 729 macrolide prescriptions, and 1608 beta-lactam prescriptions during the study period, there was no difference in 15, 30, or 90-day odds of MG-related hospitalization between fluoroquinolone or macrolide users compared to prescribed beta-lactams. (Source 29)

How much

• Reference intake: Dosing is set by the prescriber. As a position, the FDA-approved ofloxacin tablet label (DailyMed version published 23 June 2026) states the usual dose is 200 mg to 400 mg orally every 12 hours in people with normal kidney function, with the exact unit dose and duration depending on the infection. (Source 30)
• Upper limit: As a position, the same label's highest daily dose in the dosing chart is 800 mg per day (400 mg every 12 hours), and it states that in severe liver disease such as cirrhosis a maximum of 400 mg of ofloxacin per day should not be exceeded. (Source 30)
• Studied: The randomised cystitis trial gave ofloxacin 200 mg twice daily for 3 days. (Source 3)
• Studied: The pelvic inflammatory disease trial gave oral ofloxacin 400 mg twice daily for 10 days. (Source 4)
• Studied: The pharmacokinetic interaction studies used single oral doses of ofloxacin 400 mg in healthy volunteers. (Source 9)

A common belief, and what the research shows

The belief: You must avoid all calcium and all dairy while taking ofloxacin, or the antibiotic will not work.

What the research shows: The blanket rule comes from the label's class statement about metal cations. The ofloxacin-specific human studies are narrower. Milk was tested directly and did nothing: These data indicate that food and milk have a clinically insignificant effect on ofloxacin absorption. Calcium carbonate antacid was also tested and the investigators concluded: It appears that MAH and CC antacids in the doses used in this study generally do not interfere in a clinically significant manner with the bioavailability of ofloxacin, provided that an interval of at least 2 h separates the administration of these products. Iron is the one that clearly matters, cutting exposure by 25% and peak level by 36%. Simultaneous dosing with antacids was never studied, so the two-hour gap is a sensible untested precaution rather than a disproved one.

Questions and answers

What is it?

Ofloxacin is a synthetic fluoroquinolone antibiotic, taken as a tablet and also made as eye and ear drops. Almost all of an oral dose is absorbed, about 98%, with peak blood levels one to two hours after a dose, and the kidneys clear most of it. Levofloxacin is the purified active half of the same molecule. (Source 31)

What does it do in the body?

It kills bacteria by blocking two bacterial enzymes, DNA gyrase and topoisomerase IV, that the bacterium needs to copy, read and repair its DNA. It is often bactericidal at concentrations only slightly above the level that stops growth, and because its chemistry differs from penicillins, macrolides and aminoglycosides it can work against bacteria that resist those. (Source 1)

Is it good or bad for you?

Both, and the balance depends on the infection. For a simple bladder infection a 3-day course cleared the bacteria in 97% of women, and in pelvic inflammatory disease it matched the comparator regimen. But the same drug carries a boxed warning for disabling, potentially permanent tendon, nerve and brain effects plus worsening of myasthenia gravis, and the regulator now says to keep it in reserve for bronchitis and simple cystitis where alternatives exist. (Source 2)

How do you get more of it?

There is no dietary or supplement route; ofloxacin is a prescription antibiotic given for a defined course. As a position the FDA label's usual dose range is 200 to 400 mg every 12 hours in people with normal kidney function, with the course length set by the infection, from a single dose for gonorrhoea to six weeks for prostatitis. Doses are reduced when creatinine clearance is below 50 mL/min. (Source 30)

If it is harmful, what reduces it?

Ofloxacin is cleared by the kidneys within about a day of the last dose, with half-lives of roughly 4 to 5 hours and 20 to 25 hours. If it is causing a serious reaction the documented action is to stop it immediately and avoid the whole class in future; for nerve symptoms the stated purpose of stopping fast is to minimise the chance of permanent damage. (Source 31)

Why might someone be low in it or missing it?

This question does not apply in the deficiency sense; nobody needs ofloxacin in the body. People are kept off it for specific reasons: a history of myasthenia gravis, tendon disorders or previous peripheral neuropathy are avoid-conditions in the label, safety and efficacy have not been established under 18 or in pregnancy and breastfeeding, and for bronchitis and simple cystitis the label now reserves it for people with no alternative. (Source 15)

Which whole foods contain it or feed it?

No whole food contains ofloxacin. Food matters only for absorption, and less than the folklore suggests: a meal lowered the peak level 20% and delayed it by an hour without changing total absorption, and milk changed nothing at all. Iron supplements are the real problem, cutting total exposure by 25%; the label also asks for a two-hour gap from calcium, magnesium, aluminium and zinc-containing products. (Source 13)

What happens if you do not have it?

Nothing is missing if a person is not taking it; the question is what happens to an infection treated another way. In the randomised cystitis trial ciprofloxacin and co-trimoxazole performed similarly, so alternatives exist. In enteric fever the opposite applies: where resistance is high, azithromycin outperformed ofloxacin, with more than twice the failure rate on ofloxacin. (Source 7)

How can you test for it?

There is no routine blood level test for ofloxacin. The test that matters is on the bacterium, not the drug: culture and susceptibility testing before treatment identifies the organism and whether it is susceptible, and the label advises repeating it during therapy because some Pseudomonas strains develop resistance quickly. Kidney function is also checked, since the dose depends on creatinine clearance. (Source 6)

References

1. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: MICROBIOLOGY. 2026. Read the source
2. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: WARNING (boxed warning section, LOINC 34066-1). 2026. Read the source
3. The American journal of medicine. A randomized trial of short-course ciprofloxacin, ofloxacin, or trimethoprim/sulfamethoxazole for the treatment of acute urinary tract infection in women. Ciprofloxacin Urinary Tract Infection Group. - section: Results. 1999. PMID 10190377, DOI 10.1016/s0002-9343(99)00026-1. Read the source
4. Southern medical journal. Multicenter randomized trial of ofloxacin versus cefoxitin and doxycycline in outpatient treatment of pelvic inflammatory disease. Ambulatory PID Research Group. - section: Abstract (complete). 1993. PMID 8506477, DOI 10.1097/00007611-199306000-00002. Read the source
5. MMWR. Morbidity and mortality weekly report. Update to CDC's sexually transmitted diseases treatment guidelines, 2006: fluoroquinolones no longer recommended for treatment of gonococcal infections. - section: Abstract. 2007. PMID 17431378. Read the source
6. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: INDICATIONS AND USAGE. 2026. Read the source
7. The Cochrane database of systematic reviews. Fluoroquinolones for treating typhoid and paratyphoid fever (enteric fever). - section: Main results (fluoroquinolones versus current second-line options, from the Pakistan 2003-04 trial onwards). 2011. PMID 21975746, DOI 10.1002/14651858.cd004530.pub4. Read the source
8. The Cochrane database of systematic reviews. Fluoroquinolones for treating tuberculosis (presumed drug-sensitive). - section: Authors' conclusions. 2013. PMID 23744519, DOI 10.1002/14651858.cd004795.pub4. Read the source
9. British journal of clinical pharmacology. The effect of ferrous sulphate on the absorption of norfloxacin, ciprofloxacin and ofloxacin. - section: Abstract. 1994. PMID 8148225, DOI 10.1111/j.1365-2125.1994.tb04245.x. Read the source
10. Antimicrobial agents and chemotherapy. Effects of magnesium-aluminum hydroxide and calcium carbonate antacids on bioavailability of ofloxacin. - section: Abstract. 1990. PMID 2088202, DOI 10.1128/aac.34.12.2436. Read the source
11. The Journal of antimicrobial chemotherapy. Influence of oral co-administered metallic drugs on ofloxacin pharmacokinetics. - section: Abstract. 1991. PMID 1663108, DOI 10.1093/jac/28.1.87. Read the source
12. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: PRECAUTIONS - Drug Interactions. 2026. Read the source
13. European journal of clinical pharmacology. The effect of food or milk on the absorption kinetics of ofloxacin. - section: Abstract. 1991. PMID 1815968, DOI 10.1007/bf00314986. Read the source
14. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: ADVERSE REACTIONS. 2026. Read the source
15. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: WARNINGS (first part: disabling serious reactions, tendinitis and tendon rupture, peripheral neuropathy, CNS effects, myasthenia gravis, paediatric/pregnancy). 2026. Read the source
16. Archives of internal medicine. Increased risk of achilles tendon rupture with quinolone antibacterial use, especially in elderly patients taking oral corticosteroids. - section: Results. 2003. PMID 12912715, DOI 10.1001/archinte.163.15.1801. Read the source
17. Clinical drug investigation. Relative and Absolute Risk of Tendon Rupture with Fluoroquinolone and Concomitant Fluoroquinolone/Corticosteroid Therapy: Population-Based Nested Case-Control Study. - section: Results. 2019. PMID 30465300, DOI 10.1007/s40261-018-0729-y. Read the source
18. JAMA neurology. Association Between Peripheral Neuropathy and Exposure to Oral Fluoroquinolone or Amoxicillin-Clavulanate Therapy. - section: Results. 2019. PMID 31034074, DOI 10.1001/jamaneurol.2019.0887. Read the source
19. Neurology. Oral fluoroquinolone use and risk of peripheral neuropathy: a pharmacoepidemiologic study. - section: Results. 2014. PMID 25150290, DOI 10.1212/wnl.0000000000000846. Read the source
20. Drug safety. Fluoroquinolone-associated myasthenia gravis exacerbation: evaluation of postmarketing reports from the US FDA adverse event reporting system and a literature review. - section: Results. 2011. PMID 21879778, DOI 10.2165/11593110-000000000-00000. Read the source
21. BMC cardiovascular disorders. Fluoroquinolone use and aortic aneurysm or dissection: a German cohort study based on nationwide SHI-physicians outpatient claims data confirms increased risk. - section: Results. 2025. PMID 40988034, DOI 10.1186/s12872-025-05163-z. Read the source
22. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: WARNINGS (second part: hypersensitivity, CDAD, aortic aneurysm and dissection, blood glucose disturbances, gonorrhoea and syphilis). 2026. Read the source
23. Sexually transmitted infections. Treatment of mild-to-moderate pelvic inflammatory disease with a short-course azithromycin-based regimen versus ofloxacin plus metronidazole: results of a multicentre, randomised controlled trial. - section: Results. 2021. PMID 33188138, DOI 10.1136/sextrans-2020-054468. Read the source
24. JAMA cardiology. Association Between Fluoroquinolone Use and Hospitalization With Aortic Aneurysm or Aortic Dissection. - section: Results. 2023. PMID 37585175, DOI 10.1001/jamacardio.2023.2418. Read the source
25. BMC cardiovascular disorders. Fluoroquinolone use and aortic aneurysm or dissection: a German cohort study based on nationwide SHI-physicians outpatient claims data confirms increased risk. - section: Conclusions. 2025. PMID 40988034, DOI 10.1186/s12872-025-05163-z. Read the source
26. JAMA cardiology. Association Between Fluoroquinolone Use and Hospitalization With Aortic Aneurysm or Aortic Dissection. - section: Conclusions and relevance. 2023. PMID 37585175, DOI 10.1001/jamacardio.2023.2418. Read the source
27. European heart journal. Lack of association between fluoroquinolone and aortic aneurysm or dissection. - section: Conclusions. 2023. PMID 37724037, DOI 10.1093/eurheartj/ehad627. Read the source
28. Drug safety. Fluoroquinolone-associated myasthenia gravis exacerbation: evaluation of postmarketing reports from the US FDA adverse event reporting system and a literature review. - section: Conclusions. 2011. PMID 21879778, DOI 10.2165/11593110-000000000-00000. Read the source
29. Muscle & nerve. Pharmacosafety of fluoroquinolone and macrolide antibiotics in the clinical care of patients with myasthenia gravis. - section: Results. 2021. PMID 33719062, DOI 10.1002/mus.27230. Read the source
30. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: DOSAGE AND ADMINISTRATION (opening text, before the dosing table). 2026. Read the source
31. DailyMed / US National Library of Medicine (FDA label). OFLOXACIN tablet, film coated - FDA prescribing information (Structured Product Label), Modavar Pharmaceuticals LLC - section: CLINICAL PHARMACOLOGY (opening text, before the serum-concentration table). 2026. Read the source