Clotrimazole

What it is

Clotrimazole is a synthetic imidazole antifungal, sold as a 1% skin cream, gel or solution over the counter, as a 2% vaginal cream or pessary, and as a prescription 10 mg lozenge (troche) that dissolves in the mouth. It works on the fungal cell membrane, changing its permeability so that yeasts and dermatophytes stop growing and, at higher concentrations, die. Almost none of it is absorbed: after a 10 mg lozenge, mean serum concentrations were only about 5 and 3 nanograms per mL at 30 and 60 minutes.

What the research says

Clotrimazole treats infection where it is applied. Cochrane's review of 67 randomised trials found azole creams cut the risk of treatment failure in athlete's foot to about a third of placebo, and its 26-trial review of vaginal thrush found intravaginal azoles give clinical cure rates essentially the same as oral antifungals, with local irritation instead of systemic side effects. For thrush in the mouth it works but is beaten by fluconazole on eradicating the yeast and on staying symptom-free, and five-times-daily dosing hurts adherence. It is the wrong drug for any infection inside the body, and its own label says so. Despite being described as local, the lozenge raises tacrolimus blood levels in transplant recipients.

Evidence grade: Well established.

How it works

Drug class: Imidazole antifungal

Clotrimazole attacks the fungal cell membrane, altering its permeability so that the yeast or dermatophyte cannot keep its internal contents in order. At lower concentrations this stops the fungus growing; above about 20 mcg/mL it can kill Candida species outright in the laboratory. Because so little is absorbed into the blood, this effect happens only on the surface it is applied to - skin, vaginal mucosa or the lining of the mouth. (Source 1)

What it is used for

• Randomised trials show clotrimazole lozenges work but less well than oral fluconazole: a 334-patient multicentre trial found similar symptom improvement (94% versus 98%) but worse eradication of Candida (48% versus 65%) and far more relapse, and a smaller trial found clinical resolution of only 65%. Five-times-daily dosing also hurts adherence. Evidence: limited. (Source 2)
• The label restricts the prophylactic indication to these specific causes of immunosuppression and states that there are no adequate trials for other causes. The lozenge interacts with tacrolimus, which matters in transplant recipients. Evidence: limited. (Source 1)
• Cochrane's 2020 review of 26 trials found intravaginal azoles such as clotrimazole give clinical cure rates essentially equal to oral antifungals, with local irritation rather than systemic side effects. Overall risk of bias in the trials was high. Evidence: established. (Source 3)
• Cochrane found azole creams reduce treatment failure in athlete's foot with a pooled risk ratio of 0.30 versus placebo. Head to head, allylamines such as terbinafine do slightly better (RR 0.63 in favour of allylamines), and one cream trial found 73% versus 94% mycological cure. Evidence: established. (Source 4)
• Cochrane found the evidence for topical treatment of toenail infection sparse, and clotrimazole is not among the topicals with evidence of benefit. Oral terbinafine or an azole is what the nail evidence supports. Evidence: not-supported. (Source 4)
• A 1996 study in five people showed oral clotrimazole blocks the red cell Gardos channel and reduces sickle cell dehydration, with somewhat higher haemoglobin. It measured laboratory markers, not crises, and every subject developed dysuria; it has not become a treatment. Evidence: limited. (Source 5)

Interactions

• Tacrolimus (pharmacokinetic study): Clotrimazole lozenges, despite being described as local, inhibit the enzyme that clears tacrolimus and raise its blood level. When the lozenges stop, tacrolimus levels drop, which has caused under-immunosuppression after transplant. (Source 6)
• Tacrolimus (switching from voriconazole to clotrimazole) (pharmacokinetic study): Clotrimazole inhibits tacrolimus clearance less strongly than voriconazole, so swapping one antifungal for the other drops tacrolimus levels sharply unless the dose is raised. (Source 7)
• Food and drink while the lozenge dissolves (label): The lozenge has to dissolve slowly in the mouth for the drug to coat the mucosa, so eating or drinking through it shortens the contact time. The label records that saliva levels only persist for about three hours after the roughly 30 minutes a troche takes to dissolve. (Source 8)
• Spermicides, tampons, douches and other vaginal products (label): The over-the-counter vaginal cream label tells people not to use these at the same time, and warns that latex condoms and diaphragms may be damaged by the cream. (Source 9)

Stopping it

• The label limits how long the lozenge should be used, because safety and effectiveness after prolonged use were barely studied. (Source 10)
• Stopping clotrimazole lozenges is itself an event for anyone on tacrolimus: in a 97-patient study tacrolimus troughs fell in 60% of patients after the lozenges were discontinued, from a median of 8.9 ng/mL. (Source 6)
• For mouth thrush, stopping does not mean the problem is solved: in the 334-patient trial only half the clotrimazole-treated patients were still symptom-free two weeks after a 14-day course, against 82% of those given fluconazole. (Source 2)

What goes wrong

In that trial more patients stopped clotrimazole than fluconazole because of side effects. (Source 2)

• Randomized trial, Moderate certainty.
• Size: 334 patients randomised.
• Who: HIV-infected adults with oral candidiasis.
• How long: 14 days.
• Result: 7 clotrimazole patients versus 2 fluconazole patients discontinued because of side effects.
• Funding: not stated.

Seven patients treated with clotrimazole and two patients treated with fluconazole discontinued therapy because of side effects.

Liver enzyme rises are common enough with clotrimazole lozenges to be in the label's adverse reactions section. (Source 11)

• Official position, Certainty not rated.
• Size: patients in the product's clinical trials; no denominator is given in the label.
• Who: people treated with clotrimazole troches, mostly with underlying malignancy.
• How long: courses of up to 14 days, or longer for prophylaxis.
• Result: elevated SGOT reported in about 15% of patients in the clinical trials; the label says most elevations were minimal and could not be separated from other therapy and the underlying disease.
• Funding: manufacturer trial data reported in the FDA label, effective 2021-07-30.

Abnormal liver function tests have been reported in patients treated with clotrimazole troches; elevated SGOT levels were reported in about 15% of patients in the clinical trials

Clotrimazole itself can cause allergic contact dermatitis, which looks like the fungal rash it is being used to treat. (Source 12)

• Case series, Very low certainty.
• Size: 9 patients with contact allergy to imidazole antimycotics, 3 of them positive to clotrimazole.
• Who: dermatology patients patch-tested at the University of Heidelberg between 1977 and 1986.
• How long: a 10-year case series.
• Result: positive reactions: miconazole 6, clotrimazole 3, econazole 3, isoconazole 3, oxiconazole 1; no cross-reactivity with bifonazole.
• Funding: not stated.

Limit of this finding: The abstract as published misspells one drug name - "isconazole" is isoconazole, another imidazole antifungal. The quote is left exactly as the source prints it. This is nine patients collected over ten years at one clinic, so it shows that the reaction happens, not how often.

The number of positive reactions decreased in the following order: miconazole (6), clotrimazole (3), econazole (3), isconazole (3), and oxiconazole (1).

Intravaginal treatment is more often associated with local reactions, and oral treatment with systemic ones. (Source 13)

• Systematic review, Low certainty.
• Size: 16 trials, 3,155 participants for the side-effect comparison.
• Who: women with uncomplicated vulvovaginal candidiasis.
• How long: trial treatment courses.
• Result: side effects OR 1.04 (95% CI 0.84 to 1.29) oral versus intravaginal; if the intravaginal rate is 12%, the oral rate would be 10% to 15%.
• Funding: not stated.

We noted that the type of side effects differed, with intra-vaginal treatments being more often associated with local reactions, and oral treatments being more often associated with systemic effects including gastro-intestinal symptoms and headaches.

Clotrimazole lozenges, though described as acting locally, raise blood levels of tacrolimus in transplant recipients; levels fall when the lozenges stop. (Source 6)

• Cohort study, Low certainty.
• Size: 97 kidney transplant recipients on a stable tacrolimus dose.
• Who: kidney transplant recipients given clotrimazole troches for the first 30 days after transplant.
• How long: tacrolimus troughs compared 7 and 14 days before and after clotrimazole was stopped.
• Result: median trough fell by 1.3 ng/mL (CI -2.5, -1.0; P < .001) at day 7 and 2.8 ng/mL (CI -3.3, -1.6; P < .001) at day 14 from a median baseline of 8.9 ng/mL; a fall occurred in 60% of patients.
• Funding: not stated; retrospective single-centre.

The median change in tacrolimus trough level was -1.3 ng/mL (confidence interval, -2.5, -1.0; P < .001) at day 7 and -2.8 ng/mL (confidence interval, -3.3, -1.6; P < .001) at day 14 after clotrimazole discontinuation, from a median baseline of 8.9 ng/mL.

A second centre stopped using clotrimazole prophylaxis after transplant because of the same interaction and its effect on graft monitoring. (Source 14)

• Cohort study, Low certainty.
• Size: adult kidney transplant recipients at one centre, August 2019 to July 2020.
• Who: kidney transplant recipients on per-protocol standard-dose tacrolimus through 90 days.
• How long: through 90 days after transplant.
• Result: median tacrolimus trough fell from 10.5 ng/ml (IQR 8.4-12.2) to 6.6 ng/ml (IQR 5-8.7), p < 0.0001; no significant difference in for-cause allograft biopsies (4.9% vs. 9.7%, p = 0.264) or in candidiasis (1.2% vs. 5.4%, p = 0.217)
• Funding: not stated; retrospective cohort.

Limit of this finding: The fall in tacrolimus levels was clear, but neither clinical outcome this study measured differed significantly: for-cause allograft biopsies 4.9% versus 9.7% (p = 0.264) and candidiasis 1.2% versus 5.4% (p = 0.217). The authors' phrase "can potentially lead to negative allograft outcomes" is what they infer the interaction might do, not something this study demonstrated.

Our study provides further evidence of a significant drug-drug interaction between tacrolimus and clotrimazole among kidney transplant recipients that can potentially lead to negative allograft outcomes.

Taken by mouth at far higher doses as an experimental treatment for sickle cell disease, clotrimazole caused dysuria in every subject and reversible liver enzyme rises in some. (Source 5)

• Case series, Very low certainty.
• Size: 5 subjects with sickle cell anaemia.
• Who: patients with sickle cell anaemia in an open dose-escalation study.
• How long: weekly dose escalation from 10 mg/kg/day, with blood sampled three times a week.
• Result: Gardos channel inhibition and reduced red cell dehydration at 20 mg/kg/day; mild to moderate dysuria in all 5 subjects; reversible ALT and AST rise in 2 subjects at 30 mg/kg/day.
• Funding: not stated; uncontrolled pilot study of 5 people.

Adverse effects were limited to mild/moderate dysuria in all subjects, and a reversible increase in plasma alanine transaminase and aspartic transaminase levels in two subjects treated with 30 mg clotrimazole/kg/d.

Clotrimazole vaginal cream can damage latex condoms and diaphragms, which is a contraception and infection risk rather than a drug side effect. (Source 9)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: people using clotrimazole 2% vaginal cream.
• How long: 3 days of vaginal cream, up to 7 days of external cream.
• Result: no quantitative failure rate is given on the label.
• Funding: regulatory position, OTC label effective 2025-07-21.

Condoms and diaphragms may be damaged and fail to prevent pregnancy or sexually transmitted diseases (STDs).

The over-the-counter vaginal clotrimazole label puts limits on self-treatment, naming the symptoms that mean a user should stop and see a doctor rather than keep treating. (Source 9)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: adults and children 12 years of age and over self-treating a vaginal yeast infection.
• How long: the label’s 3-day vaginal course and up to 7 days of external cream.
• Result: stop use and ask a doctor if symptoms do not get better in 3 days, if symptoms last more than 7 days, or on rash or hives, abdominal pain, fever, chills, nausea, vomiting or a foul-smelling discharge; no effect size is given.
• Funding: not stated.

Stop use and ask a doctor if symptoms do not get better in 3 days symptoms last more than 7 days you get a rash or hives, abdominal pain, fever, chills, nausea, vomiting, or a foul-smelling vaginal discharge

What the evidence supports

Azole creams such as clotrimazole clear athlete's foot far more often than placebo. (Source 4)

• Systematic review, Moderate certainty.
• Size: 67 randomised controlled trials met inclusion criteria out of 144 identified papers.
• Who: people with mycologically diagnosed fungal infection of the skin and nails of the foot.
• How long: trial treatment courses, typically 1 to 6 weeks for skin.
• Result: pooled risk ratio of treatment failure for azoles 0.30 (95% CI 0.20 to 0.45); allylamines 0.33 (95% CI 0.24 to 0.44); ciclopiroxolamine 0.27 (95% CI 0.11 to 0.66)
• Funding: not stated.

Placebo-controlled trials yielded the following pooled risk ratios (RR) of treatment failure for skin infections: allylamines RR 0.33 (95% CI 0.24 to 0.44); azoles RR 0.30 (95% CI 0.20 to 0.45); ciclopiroxolamine RR 0.27 (95% CI 0.11 to 0.66); tolnaftate RR 0.19 (95% CI 0.08 to 0.44); butenafine RR 0.33 (95% CI 0.24 to 0.45); undecanoates RR 0.29 (95% CI 0.12 - 0.70).

In a larger trial using solutions rather than creams, clotrimazole for four weeks was as effective as terbinafine for one week, with similar side effect rates. (Source 15)

• Randomized trial, Moderate certainty.
• Size: 429 patients randomised (217 terbinafine, 212 clotrimazole)
• Who: patients with culture-positive interdigital tinea pedis.
• How long: terbinafine 1% solution 1 week then vehicle 3 weeks versus clotrimazole 1% solution 4 weeks; 8-week follow-up.
• Result: effective treatment 181/217 (83%) terbinafine versus 174/212 (82%) clotrimazole; per-protocol mycological cure 95% versus 91% (P = 0.05); drug-related adverse events in 13 versus 11 patients, 4 to 5% in each group.
• Funding: not stated.

Effective treatment of tinea pedis was recorded in 181 of 217 (83%) of patients treated for 1 week with terbinafine 1% solution and 174 of 212 (82%) of patients treated for 4 weeks with clotrimazole 1% solution.

For vaginal thrush, intravaginal azoles such as clotrimazole give clinical cure rates close to oral antifungals, with a different side effect pattern. (Source 3)

• Systematic review, Moderate certainty.
• Size: 26 trials, 5,007 participants.
• Who: women aged 16 and over with mycologically diagnosed uncomplicated vulvovaginal candidiasis.
• How long: short-term and long-term follow-up as defined in the trials.
• Result: clinical cure short-term OR 1.14 (95% CI 0.91 to 1.43) for oral versus intravaginal; if intravaginal cure is 77%, oral would be 75% to 83%; side effects about 12% with intravaginal treatment.
• Funding: not stated; the review judged the overall risk of bias of included trials to be high.

There was probably little or no difference shown between oral and intra-vaginal anti-fungal treatment for clinical cure at short-term follow-up (OR 1.14, 95% CI 0.91 to 1.43; 13 trials; 1859 participants; moderate-certainty evidence)

That same study is the only human evidence that clotrimazole blocks the red cell channel implicated in sickling, and it measured laboratory markers rather than clinical crises. (Source 5)

• Case series, Very low certainty.
• Size: 5 subjects.
• Who: patients with sickle cell anaemia.
• How long: weeks of dose escalation.
• Result: at 20 mg/kg/day all subjects showed Gardos channel inhibition, reduced erythrocyte dehydration, increased cell potassium and somewhat increased haemoglobin; no clinical crisis endpoint was measured.
• Funding: not stated.

At dosages of 20 mg clotrimazole/kg/d, all subjects showed Gardos channel inhibition, reduced erythrocyte dehydration, increased cell K+ content, and somewhat increased hemoglobin levels.

What the evidence does not support

Head to head, allylamines such as terbinafine cure slightly more foot infections than azoles such as clotrimazole. (Source 4)

• Systematic review, Moderate certainty.
• Size: 11 trials comparing allylamines with azoles.
• Who: people with mycologically diagnosed tinea pedis.
• How long: trial treatment courses.
• Result: risk ratio of treatment failure 0.63 (95% CI 0.42 to 0.94) in favour of allylamines.
• Funding: not stated; the earlier version of this review reported evidence of language bias in this comparison.

Meta-analysis of 11 trials comparing allylamines and azoles showed a risk ratio of treatment failure RR 0.63 (95% CI 0.42 to 0.94) in favour of allylamines.

In a one-week versus four-week comparison, terbinafine 1% cream cleared tinea pedis more often than clotrimazole 1% cream. (Source 16)

• Randomized trial, Moderate certainty.
• Size: 256 patients randomised, 211 evaluable (107 terbinafine, 104 clotrimazole)
• Who: patients with mycologically confirmed tinea pedis in 32 general practices and one hospital.
• How long: terbinafine 1 week then inert cream 3 weeks versus clotrimazole 4 weeks; assessed to week 6.
• Result: mycological cure at week 4: 93.5% terbinafine versus 73.1% clotrimazole (p = 0.0001); at week 6: 97.2% versus 83.7% (p = 0.001); effective treatment at week 4: 89.7% versus 58.7% (p = 0.0001)
• Funding: not stated; the comparison favours the sponsor's product and the clotrimazole arm was unblinded to duration.

At week four rates of mycological cure were 93.5% for terbinafine and 73.1% for clotrimazole (p = 0.0001); and at week six 97.2% for terbinafine and 83.7% for clotrimazole (p = 0.001).

For thrush in the mouth in HIV infection, a small randomised trial found clotrimazole troches clearly inferior to fluconazole tablets. (Source 17)

• Randomized trial, Low certainty.
• Size: 39 randomised, 36 evaluable.
• Who: adults with HIV infection and oral candidiasis.
• How long: 14 days of treatment with follow-up.
• Result: clinical resolution 100% fluconazole versus 65% clotrimazole (P = 0.018); mycological eradication 75% versus 20% (P = 0.004)
• Funding: not stated; single-centre and very small.

Among 36 evaluable patients, clinical resolution rates were 100 and 65%, respectively (P = 0.018). Mycological eradication rates were 75 and 20%, respectively (P = 0.004).

Clotrimazole is not absorbed enough to treat infection inside the body, and the label says so explicitly. (Source 18)

• Official position, Certainty not rated.
• Size: pharmacokinetic data in the label: mean serum concentrations of 4.98 and 3.23 nanograms/mL after a troche.
• Who: healthy volunteers given a 10 mg troche.
• How long: 30 and 60 minutes after dosing.
• Result: serum levels in the nanogram per mL range, far below antifungal concentrations.
• Funding: regulatory position, FDA label effective 2021-07-30.

Clotrimazole is not indicated for the treatment of systemic mycoses including systemic candidiasis.

Where the evidence is mixed

A much larger multicentre randomised trial found clotrimazole troches almost as good as fluconazole for clearing symptoms, but worse at eradicating the yeast and at keeping people symptom-free. (Source 2)

• Randomized trial, Moderate certainty.
• Size: 334 HIV-infected patients randomised.
• Who: HIV-infected adults with oral candidiasis.
• How long: 14 days of treatment, follow-up to week 4.
• Result: cured or improved 98% fluconazole versus 94% clotrimazole (p = NS); Candida eradicated 65% versus 48% (p = 0.005); still asymptomatic at week 2 of follow-up 82.3% versus 50.0% (p < 0.001)
• Funding: not stated (Multicenter Study Group)

Both treatments were clinically effective: 98% of evaluable fluconazole-treated patients and 94% of evaluable clotrimazole-treated patients were cured or showed improvement (p = NS).

Where the research disagrees

Whether clotrimazole lozenges are an adequate treatment for oral thrush, or clearly second-best to oral fluconazole

• Multicenter Study Group randomised trial, 334 patients (J Acquir Immune Defic Syndr, 1993), randomised multicentre trial, clinical response as primary outcome: Both treatments were clinically effective: 98% of evaluable fluconazole-treated patients and 94% of evaluable clotrimazole-treated patients were cured or showed improvement (p = NS). (Source 2)
• Single-centre randomised trial, 39 patients (Antimicrob Agents Chemother, 1990), small randomised trial with both clinical and mycological outcomes: Among 36 evaluable patients, clinical resolution rates were 100 and 65%, respectively (P = 0.018). Mycological eradication rates were 75 and 20%, respectively (P = 0.004). (Source 17)

Whether clotrimazole cream is as good as terbinafine cream for athlete's foot

• Cochrane review of topical treatments for foot infections (2007), systematic review and meta-analysis of 67 randomised trials: Meta-analysis of 11 trials comparing allylamines and azoles showed a risk ratio of treatment failure RR 0.63 (95% CI 0.42 to 0.94) in favour of allylamines. (Source 4)
• Randomised double-blind trial of terbinafine versus clotrimazole solution, 429 patients (Mycoses, 1999), randomised, double-blind, multicentre 8-week trial: Effective treatment of tinea pedis was recorded in 181 of 217 (83%) of patients treated for 1 week with terbinafine 1% solution and 174 of 212 (82%) of patients treated for 4 weeks with clotrimazole 1% solution. (Source 15)

How much

• Reference intake: There is no reference intake for an antifungal drug. The FDA lozenge label (effective 2021-07-30) states, as a position, one 10 mg troche five times a day for fourteen consecutive days for treatment, and three times daily for prophylaxis. (Source 10)
• Upper limit: No upper limit or acceptable daily intake has been set. The lozenge label instead restricts duration, saying therapy should be limited to short term use if possible because prolonged-use data are limited. The over-the-counter vaginal cream label caps the external cream at 7 days. (Source 10)
• Studied: Randomised trials in HIV-associated oral thrush gave 10 mg clotrimazole troches five times daily for 14 days. (Source 2)
• Studied: Tinea pedis trials applied clotrimazole 1% cream or solution twice daily for four weeks. (Source 15)
• Studied: The over-the-counter vaginal product is a 2% cream delivering 100 mg of clotrimazole in each applicatorful. (Source 19)
• Studied: The same over-the-counter label's course, which is a regulatory position and not a trial dose, is one applicatorful inserted at bedtime for 3 days in a row, with the external cream used up to 2 times daily for up to 7 days as needed. (Source 20)
• Studied: The sickle cell pilot study escalated oral clotrimazole from 10 mg/kg/day to 20 and 30 mg/kg/day, far above any approved dose. (Source 5)

A common belief, and what the research shows

The belief: Clotrimazole is a general antifungal, so if a cream is not clearing a rash or nail, taking or using more of it for longer will.

What the research shows: Clotrimazole acts only where you put it. Its own label says 'Clotrimazole is not indicated for the treatment of systemic mycoses including systemic candidiasis.' and records serum levels of only a few nanograms per mL after a lozenge. For nails, Cochrane found the topical evidence sparse and clotrimazole is not among the topicals shown to work; for athlete's foot, head-to-head trials favour allylamines - 'Meta-analysis of 11 trials comparing allylamines and azoles showed a risk ratio of treatment failure RR 0.63 (95% CI 0.42 to 0.94) in favour of allylamines.' A rash that does not respond may also be an allergy to clotrimazole itself, which patch-test series have documented.

Questions and answers

What is it?

Clotrimazole is a synthetic imidazole antifungal, made in a laboratory and sold as a 1% skin cream, a 2% vaginal cream or pessary, and as a 10 mg lozenge for the mouth. It is not found in food and the body does not make it. It works on fungal cell membranes rather than on human tissue. (Source 8)

What does it do in the body?

It disrupts the membrane of yeasts and dermatophytes, which stops them growing and at higher concentrations kills them. Because almost none of it is absorbed, it acts where it is applied - on skin, in the vagina, or on the lining of the mouth - and the label states it is fungistatic up to 20 mcg/mL and may be fungicidal above that. (Source 8)

Is it good or bad for you?

For the infections it is meant for it is useful and low risk: Cochrane found azole creams cut treatment failure in athlete's foot to about a third of placebo, and intravaginal clotrimazole matches oral antifungals for vaginal thrush. It is the wrong drug for anything inside the body, it is beaten by terbinafine for foot infections and by fluconazole for mouth thrush, and the lozenge produced raised liver enzymes in about 15% of trial patients. (Source 4)

How do you get more of it?

Not applicable as a nutrient. Skin and vaginal clotrimazole are sold over the counter and the lozenge is prescription-only; amounts are set by the product label or a prescriber. As a regulatory position, the lozenge label's regimen is one 10 mg troche five times a day for fourteen consecutive days, and the same section adds that therapy should be limited to short term use if possible. The over-the-counter vaginal products carry their own directions, which that label prints together with the criteria for stopping and asking a doctor. (Source 10)

If it is harmful, what reduces it?

Stopping the product is enough: practically none of it enters the bloodstream, so there is nothing to clear. The one documented consequence of stopping is in transplant recipients, where tacrolimus levels fall once the lozenges end - in one study in 60% of patients. If the problem is an allergic rash to clotrimazole itself, patch testing has found that bifonazole did not cross-react. (Source 12)

Why might someone be low in it or missing it?

Not applicable: nobody is deficient in clotrimazole. The relevant question is why a clotrimazole course fails, and the literature points to three reasons - the organism is not a fungus at all, it is a yeast or dermatophyte that responds better to an allylamine or to oral fluconazole, or the infection is inside the body where clotrimazole does not reach. (Source 18)

Which whole foods contain it or feed it?

No whole food contains clotrimazole, and no food feeds it. Food matters only in that the mouth lozenge needs about thirty minutes undisturbed to dissolve, after which useful levels persist in saliva for roughly three hours. (Source 8)

What happens if you do not have it?

Going without treatment is not dangerous for most skin or vaginal thrush, but it is not neutral either. Cochrane's placebo arms show athlete's foot persists in most untreated people: the pooled risk of treatment failure on azole was 0.30 of placebo, so roughly three times as many placebo-treated people still had the infection. Untreated oral thrush in immunosuppressed people can spread to the oesophagus, which is why prophylaxis is approved in that group. (Source 1)

How can you test for it?

There is no blood test for clotrimazole and no need for one - serum levels after a lozenge are only a few nanograms per mL. What is tested is the infection: the label asks for a KOH smear or culture before treating oral thrush, and every trial in the Cochrane reviews required mycological confirmation. Blood tests are used during lozenge treatment only to watch liver enzymes. (Source 1)

References

1. US Food and Drug Administration / openFDA drug label API. Clotrimazole troche 10 mg (labeler Hikma Pharmacuticals USA USA Inc., ANDA076387) - FDA prescribing information, INDICATIONS AND USAGE, SPL effective 2021-07-30. 2021. Read the source
2. Journal of acquired immune deficiency syndromes. Therapy for oropharyngeal candidiasis in HIV-infected patients: a randomized, prospective multicenter study of oral fluconazole versus clotrimazole troches. The Multicenter Study Group. 1993. PMID 8254467. Read the source
3. The Cochrane database of systematic reviews. Oral versus intra-vaginal imidazole and triazole anti-fungal treatment of uncomplicated vulvovaginal candidiasis (thrush). 2020. PMID 32845024, DOI 10.1002/14651858.cd002845.pub3. Read the source
4. The Cochrane database of systematic reviews. Topical treatments for fungal infections of the skin and nails of the foot. 2007. PMID 17636672, DOI 10.1002/14651858.cd001434.pub2. Read the source
5. The Journal of clinical investigation. Therapy with oral clotrimazole induces inhibition of the Gardos channel and reduction of erythrocyte dehydration in patients with sickle cell disease. 1996. PMID 8636434, DOI 10.1172/jci118537. Read the source
6. Transplantation proceedings. Impact of Clotrimazole Fungal Prophylaxis on Tacrolimus Exposure in Kidney Transplant Recipients: A Retrospective Study. 2021. PMID 33962777, DOI 10.1016/j.transproceed.2021.03.032. Read the source
7. JHLT open. Evaluation of the tacrolimus drug interaction with voriconazole vs clotrimazole in heart transplant recipients. 2024. PMID 40144266, DOI 10.1016/j.jhlto.2023.100048. Read the source
8. US Food and Drug Administration / openFDA drug label API. Clotrimazole troche 10 mg (labeler Hikma Pharmacuticals USA USA Inc., ANDA076387) - FDA prescribing information, CLINICAL PHARMACOLOGY, SPL effective 2021-07-30. 2021. Read the source
9. US Food and Drug Administration / openFDA drug label API. sunmark Clotrimazole 3 (clotrimazole 2% vaginal cream, distributed by McKesson) - FDA over-the-counter drug label, Warnings, in full: Do not use, Ask a doctor, When using this product, Stop use and ask a doctor, and the pregnancy advisory, SPL effective 2025-07-21. 2025. Read the source
10. US Food and Drug Administration / openFDA drug label API. Clotrimazole troche 10 mg (labeler Hikma Pharmacuticals USA USA Inc., ANDA076387) - FDA prescribing information, DOSAGE AND ADMINISTRATION, SPL effective 2021-07-30. 2021. Read the source
11. US Food and Drug Administration / openFDA drug label API. Clotrimazole troche 10 mg (labeler Hikma Pharmacuticals USA USA Inc., ANDA076387) - FDA prescribing information, ADVERSE REACTIONS, SPL effective 2021-07-30. 2021. Read the source
12. Contact dermatitis. Contact allergy to imidazole antimycotics. 1988. PMID 2966706, DOI 10.1111/j.1600-0536.1988.tb02743.x. Read the source
13. The Cochrane database of systematic reviews. Oral versus intra-vaginal imidazole and triazole anti-fungal treatment of uncomplicated vulvovaginal candidiasis (thrush). 2020. PMID 32845024, DOI 10.1002/14651858.cd002845.pub3. Read the source
14. Transplant infectious disease : an official journal of the Transplantation Society. Evaluation of clotrimazole prophylaxis on tacrolimus trough concentrations in kidney transplant recipients. 2022. PMID 35689488, DOI 10.1111/tid.13882. Read the source
15. Mycoses. Efficacy and tolerability of terbinafine 1% topical solution used for 1 week compared with 4 weeks clotrimazole 1% topical solution in the treatment of interdigital tinea pedis: a randomized, double-blind, multi-centre, 8-week clinical trial. 1999. PMID 10536434, DOI 10.1046/j.1439-0507.1999.00477.x. Read the source
16. BMJ (Clinical research ed.). Comparison of terbinafine and clotrimazole in treating tinea pedis. 1993. PMID 8401048, DOI 10.1136/bmj.307.6905.645. Read the source
17. Antimicrobial agents and chemotherapy. Comparison of oral fluconazole and clotrimazole troches as treatment for oral candidiasis in patients infected with human immunodeficiency virus. 1990. PMID 2073120, DOI 10.1128/aac.34.11.2267. Read the source
18. US Food and Drug Administration / openFDA drug label API. Clotrimazole troche 10 mg (labeler Hikma Pharmacuticals USA USA Inc., ANDA076387) - FDA prescribing information, WARNING (the whole section, which is one sentence long), SPL effective 2021-07-30. 2021. Read the source
19. US Food and Drug Administration / openFDA drug label API. sunmark Clotrimazole 3 (clotrimazole 2% vaginal cream, distributed by McKesson) - FDA over-the-counter drug label, Active ingredients and Purpose, SPL effective 2025-07-21. 2025. Read the source
20. US Food and Drug Administration / openFDA drug label API. sunmark Clotrimazole 3 (clotrimazole 2% vaginal cream, distributed by McKesson) - FDA over-the-counter drug label, Directions, SPL effective 2025-07-21. 2025. Read the source