Moxifloxacin

What it is

Moxifloxacin is a synthetic fluoroquinolone antibacterial, given as a 400 mg tablet once daily, by intravenous infusion, or as eye drops. It kills bacteria by inhibiting two bacterial enzymes, topoisomerase II (DNA gyrase) and topoisomerase IV, that bacteria need to copy and repair their DNA. Absorption is not affected by a high-fat meal or by yogurt, but iron and magnesium or aluminium antacids bind it in the gut and cut blood levels substantially. The FDA label approves it for community-acquired pneumonia, skin and skin structure infections, complicated intra-abdominal infections, plague, acute bacterial sinusitis and acute bacterial exacerbation of chronic bronchitis.

What the research says

For community-acquired pneumonia, meta-analyses of randomised trials put moxifloxacin on a level with beta-lactam-based standard therapy for cure and for death, with somewhat better eradication of the organism - so the case for it is equivalence, not superiority. For sinusitis and bronchitis exacerbations the evidence is weaker and the label itself tells prescribers to reserve it for people with no alternative, because the whole fluoroquinolone class carries a boxed warning for tendon rupture, peripheral neuropathy and central nervous system effects. Attempts to use it to shorten tuberculosis treatment to four months failed outright in a 1,931-patient phase 3 trial. Off label it is widely injected into the eye at cataract surgery, where pooled randomised trials show fewer cases of endophthalmitis.

Evidence grade: Well established.

How it works

Drug class: Fluoroquinolone (8-methoxyquinolone) antibacterial

Moxifloxacin kills bacteria by blocking two enzymes - DNA gyrase (topoisomerase II) and topoisomerase IV - that bacteria use to unwind, copy and repair their DNA. Human cells do not use these bacterial enzymes, which is why the drug is selective for bacteria. Resistance arises mainly through mutations in those same enzymes, reduced entry through the bacterial outer membrane, or pumps that push the drug back out. (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 moxifloxacin hydrochloride, have been associated with disabling and potentially irreversible serious adverse reactions that have occurred together [see Warnings and Precautions (5.1) ] , including: Tendinitis and tendon rupture [see Warnings and Precautions (5.2) ] Peripheral neuropathy [see Warnings and Precautions (5.3) ] Central nervous system effects [see Warnings and Precautions (5.4) ] Discontinue moxifloxacin hydrochloride immediately and avoid the use of fluoroquinolones, including moxifloxacin hydrochloride, in patients who experience any of these serious adverse reactions [see Warnings and Precautions (5.1) ]. Fluoroquinolones, including moxifloxacin hydrochloride, may exacerbate muscle weakness in patients with myasthenia gravis. Avoid moxifloxacin hydrochloride in patients with known history of myasthenia gravis [see Warnings and Precautions (5.5) ]. Because fluoroquinolones, including moxifloxacin hydrochloride, have been associated with serious adverse reactions [see Warnings and Precautions (5.1 to 5.14) ] , reserve moxifloxacin hydrochloride for use in patients who have no alternative treatment options for the following indications: Acute bacterial sinusitis [see Indications and Usage (1.6) ] Acute bacterial exacerbation of chronic bronchitis [see Indications and Usage (1.7) ]

(Source 2)

What it is used for

• Two meta-analyses of randomised trials found moxifloxacin as effective as beta-lactam-based standard therapy and other recommended antibiotics, with similar mortality and similar adverse event rates. The benefit is equivalence to existing options, not superiority. Evidence: established. (Source 3)
• Most acute sinusitis resolves without antibiotics: in Cochrane's placebo-controlled trials 86% of placebo patients were cured or improved versus 91% on antibiotic, while side effects were about 10 percentage points more common on antibiotic. The FDA label reserves moxifloxacin for this indication for people with no alternative. Evidence: limited. (Source 4)
• We did not reach a systematic review or outcome trial specific to moxifloxacin for bronchitis exacerbations in this run. The FDA label approves the indication and simultaneously reserves the drug for patients with no alternative treatment option. Evidence: unknown. (Source 2)
• Approval rests on the manufacturer's comparative trials summarised in the label; we did not reach an independent systematic review for this indication in this run. Evidence: unknown. (Source 5)
• Approval rests on the manufacturer's comparative trials summarised in the label; we did not reach an independent systematic review for this indication in this run. Evidence: unknown. (Source 5)
• There is no human efficacy evidence. The label states that human studies could not be done and the indication rests on an animal efficacy study. Evidence: unknown. (Source 1)
• The REMoxTB phase 3 trial of 1,931 patients showed moxifloxacin-containing four-month regimens were inferior to standard six-month therapy, by 6.1 and 11.4 percentage points. Faster early bacterial killing did not translate into cure. Evidence: not-supported. (Source 6)
• A meta-analysis of eight mostly non-randomised studies found higher treatment success with moxifloxacin-containing regimens (OR 1.94) without extra adverse events, but sputum culture conversion did not differ and the study designs were weak. Evidence: limited. (Source 7)
• A 2025 meta-analysis of six randomised trials (4,438 patients) found endophthalmitis reduced (RR 0.22, 95% CI 0.07 to 0.77) with no measured harm to the corneal endothelium, but endophthalmitis is so rare that the trials were small for a safety judgement and two were at high risk of bias. Evidence: limited. (Source 8)

Interactions

• Iron (ferrous sulfate and iron-containing multivitamins) (pharmacokinetic study): Iron binds moxifloxacin in the gut so much less of the antibiotic reaches the bloodstream. The label's own study found exposure cut by about 39% and peak level by 59%. (Source 9)
• Magnesium- and aluminium-containing antacids (pharmacokinetic study): Taken at the same time as an aluminium/magnesium antacid, moxifloxacin exposure fell by 60% in twelve healthy volunteers. Separating the doses reduces, but does not abolish, the loss. (Source 10)
• Zinc-containing multivitamins and other multivalent cations (label): Moxifloxacin forms chelates with metal ions, so multivitamins containing iron or zinc, sucralfate and buffered didanosine can all drop blood levels well below the intended range. (Source 11)
• Calcium supplements (pharmacokinetic study): Unlike iron and magnesium/aluminium antacids, a 500 mg calcium supplement did not meaningfully change total moxifloxacin exposure, though the peak was slightly lower and later. (Source 12)
• Yogurt and other dairy foods (pharmacokinetic study): A cup of yogurt did not change how much moxifloxacin was absorbed, and a high-fat meal did not either. This differs from some other antibiotics. (Source 13)
• Warfarin (case reports): Fluoroquinolones including moxifloxacin have been reported to increase warfarin's anticoagulant effect, so INR is monitored closely. Infection itself also raises INR, so the two causes are hard to separate. (Source 11)
• Antidiabetic medicines (insulin, sulfonylureas and others) (case reports): Both high and low blood sugar have been reported when a fluoroquinolone is taken with a diabetes medicine; serious hypoglycaemia in the claims data was confined to people with diabetes. (Source 11)

Stopping it

• The boxed warning tells prescribers to stop moxifloxacin at once, and to avoid fluoroquinolones afterwards, if tendon, nerve or central nervous system reactions appear. This is a stop-and-do-not-restart instruction, not a taper. (Source 2)
• Stopping does not guarantee the harm stops: the label records that tendinitis or tendon rupture can appear as long as several months after the course has been completed. (Source 14)
• Finishing a course early for lack of effect is not a neutral act either: the label ties incomplete or unnecessary use to resistance, and asks that the drug be used only where a susceptible bacterial cause is proven or strongly suspected. (Source 15)

What goes wrong

In the same sinusitis review, side effects were consistently more common on antibiotic than on placebo. (Source 4)

• Systematic review, Moderate certainty.
• Size: 7 of 9 placebo-controlled trials.
• Who: adults with acute maxillary sinusitis.
• How long: trial treatment courses.
• Result: median between-group difference in adverse effects 10.5% (range 2% to 23%); drop-outs for adverse effects 1.5% on antibiotic versus 1% on control.
• Funding: not stated.

Adverse effects in seven of the nine placebo-controlled studies (comparing penicillin, amoxicillin, azithromycin or moxicillin to placebo) were more common in antibiotic than in placebo groups (median of difference between groups 10.5%, range 2% to 23%).

Fluoroquinolones as a class are associated with tendon injury, including Achilles tendon rupture, in observational studies. (Source 16)

• Meta-analysis, Low certainty.
• Size: 15 observational studies.
• Who: fluoroquinolone users in the community, including people aged 60 and over.
• How long: exposure windows as defined in the individual studies.
• Result: Achilles tendon rupture OR 2.52 (95% CI 1.81-3.52), p < 0.001, I2 = 76.7%; Achilles tendinitis OR 3.95 (95% CI 3.11-5.01), p < 0.001, I2 = 0%; any tendon disorder OR 1.98 (95% CI 1.62-2.43), p < 0.001, I2 = 84.5%.
• Funding: not stated.

Limit of this finding: This paper contradicts itself about steroids. Its results say the risk estimates "did not significantly change" once the concomitant use of corticosteroids was taken into account, while its conclusion lists corticosteroids as an additional risk factor. Treat the steroid question as unsettled by this review. The pooled odds ratios themselves are unaffected, but the studies disagreed a lot with each other for rupture (I2 = 76.7%) and for any tendon disorder (I2 = 84.5%), and all 15 were observational, so they show an association and not that fluoroquinolones caused the injuries.

The results of this meta-analysis confirm the risk of tendon injuries associated with fluoroquinolones. Older age and concomitant use of corticosteroids seem to be additional risk factors for tendinopathy.

A nationwide German claims cohort found a higher rate of aortic aneurysm or dissection after fluoroquinolones than after other antibiotics. (Source 17)

• Cohort study, Low certainty.
• Size: statutory health insurance patients in Germany covering about 87% of the population, 2009 to 2017.
• Who: outpatients prescribed a fluoroquinolone versus a propensity-score-matched group given non-fluoroquinolone antibiotics.
• How long: 2009 to 2017 prescription and diagnosis records.
• Result: HR 1.56; HR 1.43 excluding patients with pneumonia or aortic dissection; HR 1.48 adjusted for underlying infections, sex and age.
• Funding: not stated.

Limit of this finding: The published abstract reports the three hazard ratios (1.56, 1.43 and 1.48) with no confidence intervals and no p-values, so how precise they are cannot be judged from what the authors reported. It is also a comparison between two groups of antibiotic users in insurance claims, which can show an association but not that fluoroquinolones caused the aortic events.

Patients treated with fluoroquinolones had a higher risk of developing AA/AAD compared to those treated with other antibiotics (HR: 1.56).

Hypoglycaemia is a reported fluoroquinolone harm with a strong disproportionality signal in the FDA adverse event database, and moxifloxacin accounted for the most severe cases. (Source 18)

• Survey study, Very low certainty.
• Size: 242,509 fluoroquinolone adverse event reports, of which 16,306 indicated hypoglycaemia signals.
• Who: spontaneous reports to the FDA Adverse Event Reporting System, 2014 Q1 to 2023 Q4.
• How long: reports over 10 years.
• Result: ciprofloxacin ROR 99.02, levofloxacin ROR 82.78; signals detected within 1 week; moxifloxacin had the most cases of severe adverse drug events.
• Funding: not stated.

A total of 242,509 AE reports linked to FQs were detected, of which 16,306 indicated hypoglycemia signals.

A matched claims cohort found more serious hypoglycaemia in fluoroquinolone users than in users of comparator antibiotics, confined to people with diabetes. (Source 19)

• Cohort study, Low certainty.
• Size: 119,112 individuals with diabetes and 917,867 without, each matched 1:1 to a comparator.
• Who: adults dispensed an oral fluoroquinolone or comparator antibiotic for specified infections, 2000 to 2015.
• How long: 2000 to 2015.
• Result: OR 1.28 (95% CI 1.04-1.57) in the whole cohort; 1.30 (95% CI 1.05-1.62) in people with diabetes; 1.06 (95% CI 0.53-2.13) in people without diabetes.
• Funding: not stated.

Limit of this finding: The authors describe the study as investigating "the causal association", but the design compares people prescribed different antibiotics and can show an association only. In people without diabetes the estimate was 1.06 with a confidence interval from 0.53 to 2.13, which spans 1 - that means no effect was measurable in that group, not that an effect was ruled out.

Fluoroquinolone users are at an increased risk of serious hypoglycemia relative to comparator antibiotic users. This association was evident only among persons diagnosed with diabetes.

Moxifloxacin prolongs the QT interval more than levofloxacin in healthy volunteers, which is why it is used as the positive control in cardiac safety studies. (Source 20)

• Blood level study, Moderate certainty.
• Size: two thorough QT studies in healthy volunteers.
• Who: healthy men and women.
• How long: single-dose crossover sessions.
• Result: moxifloxacin 400 mg prolonged QTcF more than levofloxacin 1000 and 1500 mg, with a greater concentration-related effect in women.
• Funding: not stated.

Moxifloxacin was shown to be a more potent prolonger of QT interval corrected by Fredericia (QTcF) and had a pronounced effect on J-Tpeak c. Levofloxacin had little effect on J-Tpeak c.

Across the manufacturer's trial programme the common adverse reactions were gastrointestinal and neurological, and about one patient in twenty stopped the drug because of a side effect. (Source 5)

• Official position, Certainty not rated.
• Size: 14,981 patients in 71 active-controlled phase II to IV trials.
• Who: adults treated with moxifloxacin 400 mg once daily, mean age 50 years.
• How long: usually 6 to 10 days, mean 9 days.
• Result: nausea 7%, diarrhoea 6%, headache 4%, dizziness 3%, vomiting 2%, ALT increased 1%; discontinuation for adverse reactions 5% overall.
• Funding: manufacturer trial programme reported in the FDA label.

Discontinuation of moxifloxacin due to adverse reactions occurred in 5% of patients overall, 4% of patients treated with 400 mg PO, 4% with 400 mg intravenous and 8% with sequential therapy 400 mg oral/intravenous.

The FDA label records that fluoroquinolone tendon injury can involve tendons other than the Achilles and can appear months after the course has finished. (Source 14)

• Official position, Certainty not rated.
• Size: postmarketing reports summarised in the label.
• Who: patients of all ages taking fluoroquinolones.
• How long: from hours after the first dose to several months after completing therapy.
• Result: no rate is given in the label; risk is stated to be higher over age 60, on corticosteroids, and after kidney, heart or lung transplant.
• Funding: regulatory position, FDA label effective 2024-09-18.

This adverse reaction most frequently involves the Achilles tendon, and has also been reported with the rotator cuff (the shoulder), the hand, the biceps, the thumb, and other tendons.

The FDA label states that epidemiological studies report an increased rate of aortic aneurysm and dissection within two months of fluoroquinolone use. (Source 21)

• Official position, Certainty not rated.
• Size: epidemiological studies cited in the label.
• Who: fluoroquinolone users, particularly elderly patients.
• How long: within two months of use.
• Result: no rate or hazard ratio is given in the label text.
• Funding: regulatory position, FDA label effective 2024-09-18.

Epidemiologic studies report an increased rate of aortic aneurysm and dissection within two months following use of fluoroquinolones, particularly in elderly patients.

What the evidence supports

In pooled randomised trials moxifloxacin monotherapy for community-acquired pneumonia was no better and no worse than the recommended comparator antibiotics for clinical outcome, adverse events or death. (Source 3)

• Meta-analysis, Moderate certainty.
• Size: 6,923 patients across 14 randomised controlled trials.
• Who: adults with mild-to-moderate or severe community-acquired pneumonia.
• How long: trial treatment courses, typically 7 to 14 days.
• Result: no difference in adverse events or mortality versus comparators; better pathogen eradication than beta-lactam-based therapy.
• Funding: not stated.

Fourteen RCTs, consisting of 6923 total patients, were included in the meta-analysis. No difference was found regarding the incidence of adverse events and mortality between moxifloxacin and the compared regimens.

A second meta-analysis restricted to moxifloxacin versus beta-lactam-based standard therapy found similar clinical success and similar mortality, with better microbiological eradication. (Source 22)

• Meta-analysis, Moderate certainty.
• Size: 3,903 patients across 7 randomised controlled trials.
• Who: adults with community-acquired pneumonia.
• How long: trial treatment courses.
• Result: clinical success OR 1.15 (95% CI 0.81-1.64) clinically evaluable; mortality OR 0.98 (95% CI 0.66-1.46); microbiological success OR 1.69 (95% CI 1.02-2.80)
• Funding: not stated.

Moxifloxacin monotherapy was associated with similar clinical treatment success rates [clinically evaluable population, odds ratio (OR)=1.15, 95% confidence interval (CI) 0.81-1.64; intention-to-treat population, OR=1.11, 95% CI 0.86-1.42] and similar mortality (OR=0.98, 95% CI 0.66-1.46) compared with beta-lactam-based standard therapy for CAP.

The same trial found no excess of severe adverse events on the moxifloxacin-containing regimens. (Source 6)

• Randomized trial, High certainty.
• Size: 1,931 patients randomised.
• Who: adults with smear-positive pulmonary tuberculosis.
• How long: 17 to 26 weeks of treatment.
• Result: grade 3 or 4 adverse events in 127/~670 (19%), 111/~650 (17%) and 123/~650 (19%) in the isoniazid, ethambutol and control groups.
• Funding: Funded by the Global Alliance for TB Drug Development and others.

There was no significant difference in the incidence of grade 3 or 4 adverse events, with events reported in 127 patients (19%) in the isoniazid group, 111 (17%) in the ethambutol group, and 123 (19%) in the control group.

Moxifloxacin injected into the eye at the end of cataract surgery, an off-label use, reduced postoperative endophthalmitis in pooled randomised trials. (Source 8)

• Meta-analysis, Low certainty.
• Size: 4,438 patients across 6 randomised controlled trials (5 trials for the endophthalmitis outcome)
• Who: adults having cataract surgery.
• How long: postoperative follow-up as reported in the trials.
• Result: endophthalmitis RR 0.22 (95% CI 0.07 to 0.77, p = 0.02); sensitivity analysis excluding high risk of bias RR 0.183 (95% CI 0.038 to 0.874)
• Funding: not stated; two of six trials assessed as high risk of bias.

Intracameral moxifloxacin significantly reduced the incidence of postoperative endophthalmitis compared to the control group ( n = 5 RCTs, RR: 0.22, 95% CI [0.07, 0.77], p = 0.02).

Moxifloxacin's approval for plague rests on an animal study, not on human efficacy data. (Source 23)

• Official position, Very low certainty.
• Size: an animal efficacy study.
• Who: animals; no human efficacy trial was conducted.
• How long: not stated in the label summary.
• Result: no human efficacy estimate exists for this indication.
• Funding: regulatory position, FDA label effective 2024-09-18.

Efficacy studies of moxifloxacin could not be conducted in humans with plague for feasibility reasons. Therefore, this indication is based on an efficacy study conducted in animals only

What the evidence does not support

Replacing a standard drug with moxifloxacin to shorten treatment of drug-sensitive pulmonary tuberculosis to four months failed: fewer patients had a favourable outcome than on the standard six-month regimen. (Source 6)

• Randomized trial, High certainty.
• Size: 1,931 patients randomised.
• Who: adults with uncomplicated smear-positive pulmonary tuberculosis.
• How long: 17 weeks of moxifloxacin-containing treatment versus 26 weeks control, followed for 18 months.
• Result: favourable outcome 85% (isoniazid-replaced group) and 80% (ethambutol-replaced group) versus 92% control; differences favouring control of 6.1 percentage points (97.5% CI 1.7 to 10.5) and 11.4 percentage points (97.5% CI 6.7 to 16.1)
• Funding: Funded by the Global Alliance for TB Drug Development and others.

However, noninferiority for these regimens was not shown, which indicates that shortening treatment to 4 months was not effective in this setting.

A Korean nationwide study using third-generation cephalosporins as the comparator found no increase in aortic aneurysm or dissection with fluoroquinolones. (Source 24)

• Cohort study, Low certainty.
• Size: 954,308 patients (777,109 fluoroquinolone, 177,199 cephalosporin)
• Who: adults aged 20 and over prescribed oral antibiotics at outpatient visits, 2005 to 2016.
• How long: 2005 to 2016.
• Result: adjusted HR 0.752 (95% CI 0.515-1.100); incidence 5.40 versus 8.47 per 100,000 person-years for fluoroquinolone and cephalosporin users.
• Funding: not stated.

There was no significant difference in the risk of AA/AD in patients who were administered oral FQ compared to those administered 3GC.

Where the evidence is mixed

For acute maxillary sinusitis, antibiotics as a class reduce clinical failure only slightly, because most people recover without them. (Source 4)

• Systematic review, Moderate certainty.
• Size: 1,084 participants randomised across 5 low-risk-of-bias placebo-controlled trials (9 placebo-controlled trials, 1,915 participants in total)
• Who: adults with clinically diagnosed acute maxillary sinusitis, mostly in primary care.
• How long: 7 to 15 days follow-up.
• Result: clinical failure pooled RR 0.66 (95% CI 0.47 to 0.94); cure or improvement 86% on placebo versus 91% on antibiotic, an absolute difference of about 5 percentage points.
• Funding: not stated.

In these studies antibiotics decreased the risk of clinical failure (pooled RR of 0.66, 95% CI 0.47 to 0.94, 1084 participants randomised, 1058 evaluated, moderate quality evidence). However, the clinical benefit was small. Cure or improvement rates were high in both the placebo group (86%) and the antibiotic group (91%) in these five studies.

Adding moxifloxacin to regimens for multidrug-resistant tuberculosis was associated with a higher treatment success rate, but sputum culture conversion did not differ. (Source 7)

• Meta-analysis, Low certainty.
• Size: 1,447 patients across 8 studies (retrospective studies, randomised trials and prospective cohorts)
• Who: adults with multidrug-resistant tuberculosis.
• How long: full MDR-TB treatment courses.
• Result: treatment success OR 1.94 (95% CI 1.16-3.25, P = .01); sputum culture conversion OR 1.15 (95% CI 0.82-1.60; P = 0.43); hepatotoxicity OR 0.91 (95% CI 0.64-1.30)
• Funding: not stated.

Moxifloxacin regimen was related to a significantly elevated treatment success rate compared with levofloxacin or conventional therapy regimen (OR = 1.94; 95% CI = 1.16-3.25, P = .01).

Where the research disagrees

Whether fluoroquinolones such as moxifloxacin really raise the risk of aortic aneurysm and dissection, or whether the signal is confounding by the infection being treated

• German nationwide claims cohort (BMC Cardiovascular Disorders, 2025), propensity-score-matched cohort in statutory health insurance data covering about 87% of the German population: Patients treated with fluoroquinolones had a higher risk of developing AA/AAD compared to those treated with other antibiotics (HR: 1.56). (Source 17)
• Korean nationwide study using third-generation cephalosporins as comparator (European Heart Journal, 2023), self-controlled case series plus inverse-probability-weighted Cox model 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. (Source 24)
• FDA label (effective 2024-09-18), regulatory position citing epidemiological studies, with no effect estimate given: Epidemiologic studies report an increased rate of aortic aneurysm and dissection within two months following use of fluoroquinolones, particularly in elderly patients. (Source 21)

How much

• Reference intake: There is no reference intake for an antibiotic. Dosing is set by the prescriber; the FDA label (effective 2024-09-18) gives 400 mg orally every 24 hours for adults, with the duration depending on the infection, as a regulatory position. (Source 25)
• Upper limit: The label sets no dose above 400 mg once daily for any approved indication, and specifies no dosage adjustment for renal or hepatic impairment; this is the label's position as of 2024-09-18, not an evidence-derived ceiling. (Source 25)
• Studied: REMoxTB gave moxifloxacin in place of isoniazid or ethambutol for 17 weeks within a four-drug tuberculosis regimen, followed by 9 weeks of placebo. (Source 6)
• Studied: The thorough QT studies gave healthy volunteers a single 400 mg dose of moxifloxacin as the positive control. (Source 20)

A common belief, and what the research shows

The belief: A strong, broad-spectrum antibiotic like moxifloxacin is the sensible choice for a bad sinus infection or a chest infection that will not clear.

What the research shows: Cochrane's placebo-controlled trials in acute maxillary sinusitis found that 'Cure or improvement rates were high in both the placebo group (86%) and the antibiotic group (91%) in these five studies.' - a difference of about five percentage points - while 'Adverse effects in seven of the nine placebo-controlled studies (comparing penicillin, amoxicillin, azithromycin or moxicillin to placebo) were more common in antibiotic than in placebo groups (median of difference between groups 10.5%, range 2% to 23%).' Moxifloxacin's own label responds to that arithmetic by telling prescribers to 'reserve moxifloxacin hydrochloride for use in patients who have no alternative treatment options for the following indications: Acute bacterial sinusitis'.

Questions and answers

What is it?

Moxifloxacin is a synthetic fluoroquinolone antibacterial, taken as a 400 mg tablet once a day or given by vein. It is not a nutrient and nothing in food contains it. It kills bacteria by jamming two enzymes they need to copy and repair their DNA. (Source 1)

What does it do in the body?

In the body it reaches bacteria in the lungs, skin, abdomen and eye and blocks bacterial DNA gyrase and topoisomerase IV, which kills the organism rather than merely stopping it growing. In pneumonia trials that translated into cure rates equal to beta-lactam-based standard therapy, with better eradication of the organism. (Source 22)

Is it good or bad for you?

It depends entirely on the infection. For pneumonia it matches standard therapy. For sinusitis and bronchitis the gain over no antibiotic is small - 91% versus 86% cured or improved in Cochrane's placebo trials - while the drug carries a boxed warning for tendon rupture, nerve damage and central nervous system effects. That is why regulators restrict it to people with no alternative for those two conditions. (Source 2)

How do you get more of it?

Not applicable in the usual sense. Moxifloxacin is prescription-only and the amount is set by the prescriber, not by the person taking it; the label's adult dose is a single 400 mg tablet every 24 hours with the length depending on the infection. No food, drink or supplement supplies it. (Source 25)

If it is harmful, what reduces it?

The only documented way to reduce exposure is to stop the drug, which the label instructs prescribers to do immediately if tendon, nerve or central nervous system reactions appear. The kidneys and liver clear it over about half a day, so levels fall quickly after the last dose, but some reported harms outlast the drug. (Source 2)

Why might someone be low in it or missing it?

Not applicable: moxifloxacin is a manufactured medicine, not something the body makes or stores, so nobody is deficient in it. What can go wrong is the reverse - a dose that does not work because something was taken with it. Iron, zinc and magnesium or aluminium antacids bind it in the gut and can push blood levels well below the intended range. (Source 11)

Which whole foods contain it or feed it?

No whole food contains moxifloxacin. On the question of food that affects it, the label's studies found that a high-fat meal and a cup of yogurt made no difference to absorption, so unlike some antibiotics it is not blocked by dairy. Iron and mineral supplements, and magnesium or aluminium antacids, are the products that matter. (Source 13)

What happens if you do not have it?

This is the question of going without the antibiotic, and the answer differs by condition. For acute sinusitis most people recover anyway: 86% of placebo patients in Cochrane's trials were cured or improved. For bacterial pneumonia, plague or a complicated intra-abdominal infection, untreated infection can be fatal, which is why effective antibacterial treatment is not optional there. (Source 4)

How can you test for it?

There is no routine blood test for moxifloxacin itself in ordinary care. What is tested is the bacterium: culture and susceptibility testing decides whether the drug can work, and the label asks that it be used only where a susceptible organism is proven or strongly suspected. During treatment, blood glucose and liver enzymes are the monitoring tests the label names. (Source 15)

References

1. US Food and Drug Administration / openFDA drug label API. Moxifloxacin Hydrochloride tablet (labeler A-S Medication Solutions, ANDA202632) - FDA prescribing information, section 12.4 Microbiology (Mechanism of Action and Resistance), SPL effective 2024-09-18. 2024. Read the source
2. US Food and Drug Administration / openFDA drug label API. Moxifloxacin Hydrochloride tablet, film coated - FDA prescribing information (boxed warning), SPL effective 2024-09-18. 2024. Read the source
3. Journal of chemotherapy (Florence, Italy). Treatment of community-acquired pneumonia with moxifloxacin: a meta-analysis of randomized controlled trials. 2012. PMID 23182045, DOI 10.1179/1973947812y.0000000028. Read the source
4. The Cochrane database of systematic reviews. Antibiotics for acute maxillary sinusitis in adults. 2014. PMID 24515610, DOI 10.1002/14651858.cd000243.pub3. Read the source
5. US Food and Drug Administration / openFDA drug label API. Moxifloxacin Hydrochloride tablet (labeler A-S Medication Solutions, ANDA202632) - FDA prescribing information, section 6.1 Clinical Trials Experience (discontinuations and Table 2 common adverse reactions), SPL effective 2024-09-18. 2024. Read the source
6. The New England journal of medicine. Four-month moxifloxacin-based regimens for drug-sensitive tuberculosis. 2014. PMID 25196020, DOI 10.1056/nejmoa1407426. Read the source
7. Medicine. Meta-analysis on Effectiveness and Safety of Moxifloxacin in Treatment of Multidrug Resistant Tuberculosis in Adults. 2020. PMID 32569195, DOI 10.1097/md.0000000000020648. Read the source
8. Frontiers in medicine. Intracameral moxifloxacin for endophthalmitis prophylaxis after cataract surgery: a systematic review and meta-analysis. 2025. PMID 41585215, DOI 10.3389/fmed.2025.1704056. Read the source
9. US Food and Drug Administration / openFDA drug label API. Moxifloxacin Hydrochloride tablet (labeler A-S Medication Solutions, ANDA202632) - FDA prescribing information, section 12.3 Pharmacokinetics, Drug-Drug Interactions, Iron study, SPL effective 2024-09-18. 2024. Read the source
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