Patients taking nevirapine (Viramune) should not take the following drugs:

• Hypericin (St John’s wort), which can reduce blood levels of nevirapine.
• Ketoconazole (Nizoral), due to lowered ketoconazole levels.
• Rifampicin (Rifadin / Rimactane), due to low nevirapine levels^[1][2].

Taking nevirapine with a protease reduces the concentration of the protease inhibitor in the blood. Consequently, the following dose adjustments are recommended:

• Indinavir (Crixivan) should be taken at a dose of 1000mg every 8 hours or with ritonavir (Norvir) boosting indinavir.
• Ritonavir-boosted lopinavir(Kaletra) should be taken at a dose of four capsules or three tablets twice a day^[3].
• Saquinavir (Invirase) is not recommended in patients taking nevirapine^[4].

Combining efavirenz with nevirapine is not recommended due to an increased frequency of side effects^[5].

Patients taking nevirapine should also take non-standard doses of the following drugs, or take them with caution:

• Amoxicillin (Amoxil) levels are increased by nevirapine, increasing the risk of side-effects.
• Doxycycline (Vibramycin / Vibramycin-D) levels are reduced by nevirapine.
• Erythromycin (Erymax / Erythrocin / Erythroped / Erythroped A) levels are increased by nevirapine, increasing the risk of side-effects.
• Felodipine (Plendil) levels are reduced by nevirapine.
• Fluconazole (Diflucan) can cause the concentration of nevirapine to double, increasing the risk of side-effects. It should be used with caution^[6].
• Griseofulvin (Grisovin) levels are reduced by nevirapine.
• Methadone hydrochloride (Methadose) levels are reduced by nevirapine, patients taking both drugs should be closely monitored for withdrawal symptoms, and the methadone dose adjusted if necessary^[7][8].
• Metronidazole (Flagyl / Flagyl S / Metroyl) levels are reduced by nevirapine.
• Nifedipine (Adalat) levels are reduced by nevirapine.
• Quinidine (Kinidin Dureles) levels are reduced by nevirapine.
• Sildenafil (Viagra) levels are increased by nevirapine, and it should be taken at a reduced dose or 25mg.
• Tadalafil (Cialis) levels are increased by nevirapine, and it should be taken at a reduced dose.
• Theophylline levels are reduced by nevirapine.
• Vardenafil (Levitra) should be taken at a lower dose in patients taking nevirapine.
• Warfarin levels are reduced by nevirapine.

Nevirapine may also reduce levels of beta-blockers and steroids. It also reduces the effectiveness of oral contraceptives and alternative forms of birth control are recommended^[9].