Fulcover Drug Interactions

Drugs affecting the metabolism of Itraconazole: Interaction studies have been performed with rifampicin, rifabutin and phenytoin. Since the bioavailability of Itraconazole and hydroxyitraconazole was decreased in these studies to such an extent that efficacy may be considerably reduced, the combination of Itraconazole with these potent enzyme inducers is not recommended. No formal study data are available for other enzyme inducers, such as carbamazepine, phenobarbital and isoniazid, but similar effects should be anticipated.
Effects of Itraconazole on the metabolism of other drugs: Itraconazole can inhibit the metabolism of drugs that are substrates for cytochrome 3A isoenzymes. This can result in an increase and/or a prolongation of their effects, including side effects. After stopping treatment, Itraconazole plasma levels decline gradually, depending on the dose and duration of treatment. This should be taken into account when the inhibitory effect of Itraconazole on co-administered drugs is considered.
Examples are: Drugs which must not be used during treatment with Itraconazole: Terfenadine, astemizole, mizolastine, cisapride, triazolam, oral midazolam, dofetilide, quinidine, pimozide, CYP3A4 metabolised HMG-CoA reductase inhibitors such as simvastatin and lovastatin. Caution should be exercised when co-administering Itraconazole with calcium channel blockers. In addition to possible pharmacokinetic interactions involving the drug metabolising enzyme CYP3A4, calcium channel blockers can have negative inotropic effects which may be additive to those of Itraconazole. If the following are co-administered with Itraconazole, their plasma levels, clinical effects and possible side effects should be monitored. The dose of these drugs may need to be reduced during co-administration with Itraconazole: Oral anticoagulants; HIV protease inhibitors such as ritonavir, indinavir, saquinavir; Certain antineoplastic agents such as vinca alkaloids, busulphan, docetaxel and trimetrexate; CYP3A4 metabolised calcium channel blockers such as dihydropyridines and verapamil; Certain immunosuppressive agents: cyclosporin, tacrolimus, sirolimus.