Ketoconazole (Page 3 of 6)

1. Effects of ketoconazole on other drugs

1.1 Systemic exposure to the following drugs is significantly increased by coadministration of ketoconazole. Concomitant use of these drugs with ketoconazole tablets USP, 200 mg is contraindicated
Alprazolam, midazolam, triazolam

Co-administration of ketoconazole tablets with alprazolam, midazolam, or triazolam has resulted in elevated plasma concentrations of these drugs. This may potentiate and prolong hypnotic and sedative effects, especially with repeated or chronic administration of these agents. Concomitant administration of ketoconazole tablets with alprazolam, oral midazolam, and oral triazolam is contraindicated. (See CONTRAINDICATIONS and WARNINGS sections.) Special precaution and patient monitoring are required with concomitant parenteral midazolam, because the sedative effect may be prolonged.

Cisapride

Oral ketoconazole potently inhibits the metabolism of cisapride resulting in a mean eight-fold increase in AUC of cisapride, which can lead to prolongation of QT interval. Therefore concomitant administration of ketaconazole tablets with cisapride is contraindicated. (See BOXED WARNING, CONTRAINDICATIONS, and WARNINGS sections.)

Dofetilide

The class III antiarrhythmic dofetilide is known to prolong the QT interval. The potential increase in dofetilide plasma concentrations when administered concomitantly with ketoconazole could result in serious cardiovascular events including QTc prolongation and rare occurrences of torsades de pointes. Therefore, concomitant administration of ketoconazole tablets with dofetilide is contraindicated. (See BOXED WARNING, CONTRAINDICATIONS, and WARNINGS sections.)

Eplerenone

Ketoconazole increases the eplerenone AUC by roughly 5-fold, thereby increasing the risk for hyperkalemia and hypotension. Co-administration of ketoconazole and eplerenone is contraindicated. (See CONTRAINDICATIONS section.)

Ergot Alkaloids

Elevated concentrations of ergot alkaloids can cause ergotism, i.e., a risk for vasospasm potentially leading to cerebral ischemia and/or ischemia of the extremities. Concomitant administration of ergot alkaloids such as dihydroergotamine and ergotamine with ketoconazole tablets is contraindicated. (See CONTRAINDICATIONS section.)

HMG-CoA Enzyme Inhibitors (lovastatin, simvastatin)

Co-administration of ketoconazole with CYP3A4-metabolized HMG-CoA reductase inhibitors such as simvastatin, and lovastatin, may increase the risk of skeletal muscle toxicity, including rhabdomyolysis. Concomitant administration of ketoconazole tablets with these HMG-CoA reductase inhibitors is contraindicated. (See CONTRAINDICATIONS and WARNINGS sections.)

Nisoldipine

Pre-treatment with and concomitant administration of ketoconazole resulted in a 24-fold and 11-fold increase in mean AUC and Cmax of nisoldipine, respectively, compared with treatment with nisoldipine 5 mg alone. Concomitant administration of ketoconazole with nisoldipine is contraindicated. (See CONTRAINDICATIONS section.)

Pimozide

Pimozide is known to prolong the QT interval and is partially metabolized by CYP3A4. Co-administration of ketoconazole and pimozide could result in serious cardiovascular events including QTc prolongation and rare occurrences of torsades de pointes, and is therefore contraindicated. (See BOXED WARNING, CONTRAINDICATIONS, and WARNINGS sections.)

Quinidine

The class IA antiarhythmic quinidine is known to prolong the QT interval. The potential increase in quinidine plasma concentrations when administered concomitantly with ketoconazole could result in serious cardiovascular events including QTc prolongation and rare occurrences of torsades de pointes. Therefore, concomitant administration of ketoconazole tablets with quinidine is contraindicated. (See BOXED WARNING, CONTRAINDICATIONS, and WARNINGS sections.)

1.2 Co-administration of ketoconazole with the following agents was shown or is expected to result in increased exposure to these drugs. Therefore, careful monitoring of plasma concentrations or adverse events of these drugs is recommended. Adjustment of dosage of these drugs may be needed
Alfentanil, sufentanil, fentanyl

In vitro data suggest that alfentanil, sufentanil and fentanyl are metabolized by CYP3A4. Concomitant administration of ketoconazole tablets and alfentanil, sufentanil, or fentanyl may increase plasma concentrations of the latter drugs.

Amlodipine, felodipine, nicardipine, nifedipine

CYP3A4 metabolized calcium channel blockers such as amlodipine, felodipine, nicardipine, and nifedipine should be used cautiously with ketoconazole tablets as ketoconazole may cause several-fold increases in plasma concentrations of these calcium channel blockers.

Bosentan

Concomitant administration of ketoconazole increased the Cmax and AUC of bosentan 2.1- and 2.3 – fold, respectively. No dosage adjustment of bosentan is needed but close monitoring for increased bosentan-associated adverse effects is recommended.

Buspirone

Concomitant administration of buspirone with ketoconazole may result in significant increases in plasma concentrations of buspirone. When administered with ketoconazole tablets, a low initial dose of buspirone with subsequent dosage adjustment based on clinical assessment is recommended.

Busulfan

Ketoconazole tablets may decrease the clearance and thus increase the systemic exposure to busulfan.

Carbamazepine

In vivo studies have demonstrated an increase in plasma carbamazepine concentrations in subjects concomitantly receiving ketoconazole. Close monitoring of plasma carbamazepine concentrations is recommended whenever ketoconazole is given to patients stabilized on carbamazepine therapy.

Cilostazol

Ketoconazole had been shown to increase both cilostazol AUC and Cmax by about two-fold when administered concurrently. Co-administration of ketoconazole with cilostazol resulted in increased incidences of adverse effects, such as headache. When ketoconazole tablets is administered concomitantly with cilostazol, the prescriber should consider up to a 50% reduction in cilostazol dosage.

Cyclosporine

Ketoconazole tablets may alter the metabolism of cyclosporine, thereby resulting in elevated cyclosporine plasma concentrations. Dosage adjustment may be required if cyclosporine or tacrolimus is given concomitantly with ketoconazole tablets.

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.

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