General
Ketoconazole tablets have been demonstrated to lower serum testosterone. Once therapy with ketoconazole tablets has been discontinued, serum testosterone levels return to baseline values. Testosterone levels are impaired with doses of 800 mg per day and abolished by 1600 mg per day. Clinical manifestations of decreased testosterone concentrations may include gynecomastia, impotence and oligospermia.
Information for Patients
Patients should be instructed to report any signs and symptoms which may suggest liver dysfunction so that appropriate biochemical testing can be done. Such signs and symptoms may include unusual fatigue, anorexia, nausea and/or vomiting, abdominal pain, jaundice, dark urine or pale stools (see WARNINGS section).
Drug Interactions
Ketoconazole is mainly metabolized through CYP3A4. Other substances that either share this metabolic pathway or modify CYP3A4 activity may influence the pharmacokinetics of ketoconazole. Similarly, ketoconazole may modify the pharmacokinetics of other substances that share this metabolic pathway. Ketoconazole is a potent CYP3A4 inhibitor and a P-glycoprotein inhibitor. When using concomitant medication, the corresponding label should be consulted for information on the route of metabolism and the possible need to adjust dosages.
Interaction studies have only been performed in adults. The relevance of the results from these studies in pediatric patients is unknown.
Drugs that may decrease ketoconazole plasma concentrations
Drugs that reduce the gastric acidity (e.g. acid neutralizing medicines such as aluminum hydroxide, or acid secretion suppressors such as H2-receptor antagonists and proton pump inhibitors) impair the absorption of ketoconazole from ketoconazole tablets. These drugs should be used with caution when coadministered with ketoconazole tablets:
Ketoconazole tablets should be administered with an acidic beverage (such as non-diet cola) upon co-treatment with drugs reducing gastric acidity.
Acid neutralizing medicines (e.g. aluminum hydroxide) should be administered at least 1 hour before or 2 hours after the intake of ketoconazole tablets.
Upon coadministration, the antifungal activity should be monitored and the ketoconazole tablets dose increased as deemed necessary.
Coadministration of ketoconazole tablets with potent enzyme inducers of CYP3A4 may decrease the bioavailability of ketoconazole to such an extent that efficacy may be reduced. Examples include:
Antibacterials: isoniazid, rifabutin (see also under 'DRUGS THAT MAY HAVE THEIR PLASMA CONCENTRATIONS INCREASED'), rifampicin.
Anticonvulsants: carbamazepine (see also under 'DRUGS THAT MAY HAVE THEIR PLASMA CONCENTRATIONS INCREASED'), phenytoin.
Antivirals: efavirenz, nevirapine.
Therefore, administration of potent enzyme inducers of CYP3A4 with ketoconazole tablets is not recommended. The use of these drugs should be avoided from 2 weeks before and during treatment with ketoconazole tablets, unless the benefits outweigh the risk of potentially reduced ketoconazole efficacy. Upon coadministration, the antifungal activity should be monitored and the ketoconazole tablets dose increased as deemed necessary.
Drugs that may increase ketoconazole plasma concentrations
Potent inhibitors of CYP3A4 (e.g. antivirals such as ritonavir, ritonavir-boosted darunavir and ritonavir-boosted fosamprenavir) may increase the bioavailability of ketoconazole. These drugs should be used with caution when coadministered with ketoconazole tablets. Patients who must take ketoconazole tablets concomitantly with potent inhibitors of CYP3A4 should be monitored closely for signs or symptoms of increased or prolonged pharmacologic effects of ketoconazole, and the ketoconazole tablets dose should be decreased as deemed necessary. When appropriate, ketoconazole plasma concentrations should be measured.
Drugs that may have their plasma concentrations increased by ketoconazole
Ketoconazole can inhibit the metabolism of drugs metabolized by CYP3A4 and can inhibit the drug transport by P-glycoprotein, which may result in increased plasma concentrations of these drugs and/or their active metabolite(s) when they are administered with ketoconazole. These elevated plasma concentrations may increase or prolong both therapeutic and adverse effects of these drugs. CYP3A4-metabolized drugs known to prolong the QT interval may be contraindicated with ketoconazole tablets, since the combination may lead to ventricular tachyarrhythmias, including occurrences of torsade de pointes, a potentially fatal arrhythmia.
Examples of drugs that may have their plasma concentrations increased by ketoconazole presented by drug class with advice regarding coadministration with ketoconazole tablets:
Drug Class
Contraindicated
Not
Recommended
Use with Caution
Comments
Under no circumstances should the drug be coadministered with ketoconazole tablets, and up to one week after discontinuation of treatment with ketoconazole.
The use of the
drug should be
avoided during
and up to one
week after
discontinuation
of treatment with
ketoconazole
tablets, unless
the benefits
outweigh the
potentially
increased risks
of side effects. If
coadministration
cannot be
avoided, clinical
monitoring for signs or symptoms of increased or prolonged effects or side effects of the interacting drug is recommended, and its dosage should be
reduced or
interrupted as
deemed
necessary. When
appropriate,
plasma
concentrations
should be
measured. The
label of the
coadministered
drug should be
consulted for
information on
dose adjustment and adverse effects.
Careful monitoring is recommended when the drug is coadministered with ketoconazole tablets. Upon coadministration, patients should be monitored closely for signs or symptoms of increased or prolonged effects or side effects of the interacting drug, and its dosage should be reduced as deemed necessary. When appropriate, plasma concentrations should be measured. The label of the coadministered drug should be consulted for information on dose adjustment and adverse effects.
Alpha Blockers
Tamsulosin
Analgesics
methadone
alfentanil, buprenorphine IV and sublingual, fentanyl, oxycodone, sufentanil
Methadone: The potential increase in plasma concentrations of methadone when coadministered with ketoconazole tablets may increase the risk of serious cardiovascular events including QT prolongation and torsade de pointes, or respiratory or CNS depression. [See CONTRAINDICATIONS.]
Fentanyl: The potential increase in plasma concentrations of fentanyl when coadministered with ketoconazole tablets may increase the risk of potentially fatal respiratory depression.
Sufentanil: No human pharmacokinetic data of an interaction with ketoconazole are available. In vitro data suggest that sufentanil is metabolized by CYP3A4 and so potentially increased sufentanil plasma concentrations would be expected when coadministered with ketoconazole tablets.
Antiarrhythmics
disopyramide, dofetilide, dronedarone, quinidine
digoxin
Disopyramide, dofetilide, dronedarone, quinidine: The potential increase in plasma concentrations of these drugs when coadministered with ketoconazole may increase the risk of serious cardiovascular events including QT prolongation. Digoxin: Rare cases of elevated plasma concentrations of digoxin have been reported. It is not clear whether this was due to the combination of therapy. It is, therefore, advisable to monitor digoxin concentrations in patients receiving ketoconazole.
Antibacterials
rifabutin
telithromycin
Rifabutin: see also under 'DRUGS THAT MAY DECREASE KETOCONAZOLE PLASMA CONCENTRATIONS'.
Telithromycin: A multiple- dose interaction study with ketoconazole showed that Cmax of telithromycin was increased by 51% and AUC by 95%.
Anticoagulants and Antiplatelet Drugs
rivaroxaban
cilostazol, coumarins, dabigatran
Cilostazol: Concomitant administration of single doses of cilostazol 100 mg and ketoconazole 400 mg approximately doubled cilostazol concentrations and altered (increase/decrease) the concentrations of the active metabolites of cilostazol.
Coumarins: Ketoconazole may enhance the anticoagulant effect of coumarin-like drugs, thus the anticoagulant effect should be carefully titrated and monitored.
Dabigatran: In patients with moderate renal impairment (CrCL 50 mL/min to ≤ 80 mL/min), consider reducing the dose of dabigatran to 75 mg twice daily when it is coadministered with ketoconazole.
Anticonvulsants
carbamazepine
Carbamazepine: In vivo studies have demonstrated an increase in plasma carbamazepine concentrations in subjects concomitantly receiving ketoconazole. In addition, the bioavailability of ketoconazole may be reduced by carbamazepine.
Antidiabetics
repaglinide, saxagliptin
Antihelmintics and Antiprotozoals
praziquantel
Antimigraine Drugs
ergot alkaloids, such as dihydroergotamine, ergometrine (ergonovine), ergotamine, methylergometrine (methylergonovine)
eletriptan
Ergot alkaloids: The potential increase in plasma concentrations of ergot alkaloids when coadministered with ketoconazole tablets may increase the risk of ergotism, i.e., a risk for vasospasm potentially leading to cerebral ischemia and/or ischemia of the extremities.
Eletriptan: Eletriptan should be used with caution with ketoconazole, and specifically, should not be used within at least 72 hours of treatment with ketoconazole.
Antineoplastics
irinotecan
dasatinib, lapatinib, nilotinib
bortezomib, busulphan, docetaxel, erlotinib, imatinib, ixabepilone, paclitaxel, trimetrexate, vinca alkaloids
Irinotecan: The potential increase in plasma concentrations of irinotecan when coadministered with ketoconazole tablets may increase the risk of potentially fatal adverse events.
Docetaxel: In the presence of ketoconazole, the clearance of docetaxel in cancer patients was shown to decrease by 50%.
Antipsychotics, Anxiolytics and Hypnotics
alprazolam, lurasidone, oral midazolam, pimozide, triazolam
aripiprazole, buspirone, haloperidol, midazolam IV, quetiapine, ramelteon, risperidone
Alprazolam, midazolam, triazolam: Coadministration of ketoconazole tablets with oral midazolam or triazolam, or alprazolam may cause several-fold increases in plasma concentrations of these drugs. This may potentiate and prolong hypnotic and sedative effects, especially with repeated dosing or chronic administration of these agents.
Pimozide: The potential increase in plasma concentrations of pimozide when coadministered with ketoconazole tablets may increase the risk of serious cardiovascular events including QT prolongation and torsade de pointes.
Aripiprazole: Coadministration of ketoconazole (200 mg/day for 14 days) with a 15 mg single dose of aripiprazole increased the AUC of aripiprazole and its active metabolite by 63% and 77%, respectively. The effect of a higher ketoconazole dose (400 mg/day) has not been studied. When ketoconazole is given concomitantly with aripiprazole, the aripiprazole dose should be reduced to one-half of the recommended dose.
Buspirone: Ketoconazole is expected to inhibit buspirone metabolism and increase plasma concentrations of buspirone. If a patient has been titrated to a stable dosage on buspirone, a dose reduction of buspirone may be necessary to avoid adverse events attributable to buspirone or diminished anxiolytic activity.
Antivirals
indinavir, maraviroc, saquinavir
Beta Blockers
nadolol
Calcium Channel Blockers
felodipine, nisoldipine
other dihydropyridines,
verapamil
Calcium channel blockers can have a negative inotropic effect which may be additive to those of ketoconazole. The potential increase in plasma concentrations of calcium channel blockers when co-administered with ketoconazole tablets may increase the risk of edema and congestive heart failure.
Dihydropyridines: Concomitant administration of ketoconazole tablets may cause several-fold increases in plasma concentrations of dihydropyridines.
Cardiovascular Drugs, Miscellaneous
ranolazine
aliskiren, bosentan
Ranolazine: The potential increase in plasma concentrations of ranolazine when coadministered with ketoconazole tablets may increase the risk of serious cardiovascular events including QT prolongation.
Bosentan: Coadministration of bosentan 125 mg twice daily and ketoconazole, increased the plasma concentrations of bosentan by approximately 2-fold in normal volunteers. No dose adjustment of bosentan is necessary, but patients should be monitored for increased pharmacologic effects and adverse reactions of bosentan.
Diuretics
eplerenone
The potential increase in plasma concentrations of eplerenone when coadministered with ketoconazole tablets may increase the risk of hyperkalemia and hypotension.
Gastrointestinal Drugs
cisapride
aprepitant
Cisapride: Oral ketoconazole potently inhibits the metabolism of cisapride resulting in a mean eight-fold increase in AUC of cisapride, which can lead to serious cardiovascular events including QT prolongation.
Immunosuppressants
everolimus, rapamycin (also known as sirolimus), temsirolimus
budesonide, ciclesonide,
cyclosporine, dexamethasone,
fluticasone, methylprednisolone,
tacrolimus
Rapamycin (sirolimus): Ketoconazole tablets 200 mg daily for 10 days increased the Cmax and AUC of a single 5 mg dose of sirolimus by 4.3-fold and 10.9-fold, respectively in 23 healthy subjects.
Fluticasone: Coadministration of fluticasone propionate and ketoconazole is not recommended unless the potential benefit to the patient outweighs the risk of systemic corticosteroid side effects.
Lipid Regulating Drugs
lovastatin, simvastatin
atorvastatin
The potential increase in plasma concentrations of atorvastatin, lovastatin and simvastatin when coadministered with ketoconazole tablets may increase the risk of skeletal muscle toxicity, including rhabdomyolysis.
Respiratory Drugs
salmeterol
Urological Drugs
fesoterodine, sildenafil,
solifenacin, tadalafil,
tolterodine, vardenafil
Vardenafil: A single dose of 5 mg of vardenafil should not be exceeded when coadministered with ketoconazole.
Other
colchicine, in subjects with renal or hepatic impairment; tolvaptan
colchicine
alcohol, cinacalcet
Colchicine: The potential increase in plasma concentrations of colchicine when coadministered with ketoconazole tablets may increase the risk of potentially fatal adverse events.
Tolvaptan: Ketoconazole 200 mg administered with tolvaptan increased tolvaptan exposure by 5-fold. Larger doses would be expected to produce larger increases in tolvaptan exposure. There is not adequate experience to define the dose adjustment that would be needed to allow safe use of tolvaptan with strong CYP3A inhibitors such as ketoconazole.
Alcohol: Exceptional cases have been reported of a disulfiram-like reaction to alcohol, characterized by flushing, rash, peripheral edema, nausea and headache. All symptoms completely resolved within a few hours.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Ketoconazole did not show any signs of mutagenic potential when evaluated using the dominant lethal mutation test or the Ames Salmonella microsomal activator assay. Ketoconazole was not carcinogenic in an 18-month, oral study in Swiss albino mice or a 24-month oral carcinogenicity study in Wistar rats at dose levels of 5, 20 and 80 mg/kg/day. The high dose in these studies was approximately 1× (mouse) or 2× (rat) the clinical dose in humans based on a mg/m2 comparison.
Pregnancy
Teratogenic effects
Ketoconazole has been shown to be teratogenic (syndactylia and oligodactylia) in the rat when given in the diet at 80 mg/kg/day (2 times the maximum recommended human dose, based on body surface area comparisons). However, these effects may be related to maternal toxicity, evidence of which also was seen at this and higher dose levels.
There are no adequate and well controlled studies in pregnant women. Ketoconazole tablets should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Nonteratogenic Effects
Ketoconazole has also been found to be embryotoxic in the rat when given in the diet at doses higher than 80 mg/kg during the first trimester of gestation.
In addition, dystocia (difficult labor) was noted in rats administered oral ketoconazole during the third trimester of gestation. This occurred when ketoconazole was administered at doses higher than 10 mg/kg (about one fourth the maximum human dose, based on body surface area comparison).
Nursing Mothers
Ketoconazole has been shown to be excreted in the milk. Mothers who are under treatment with ketoconazole tablets should not breast feed.
Pediatric Use
Ketoconazole tablets have not been systematically studied in children of any age, and essentially no information is available on children under 2 years. Ketoconazole tablets should not be used in pediatric patients unless the potential benefit outweighs the risks.