INDINAVIR & SIMILAR HIV PROTEASE INHIBITORS ARE METABOLISED MAINLY BY CYTOCHROME P450 ISOENZYMES OF THE CYP3A FAMILY. RIFAMPCIN, CARBAMAZEPINE, PHENOBARBITONE, AND PHENYTOIN REDUCE THE PLASMA CONCENTRATIONS OF RITONAVIR. IT MAY REDUCE PLASMA CONCENTRATION OF THEOPHYLLINE AND HORMONAL CONTRACEPTIVES. CISAPRIDE & TERFENADINE ARE CONTRAINDICATED. ERYTHROMYCIN ONLY NEEDS DOSE REDUCTION AT ITS HIGH DOSE LEVELS.
ANALGESICS - OPIOID ANALGESICS LIKE PETHIDINE & DEXTROPROPOXYPHENE MAY HAVE INCREASED SERUM LEVELS DUE TO INHIBITED METABOLISM.
ANTIARRHYTHMICS - AMIODARONE & OTHER ANTIARRHYTHMICS METABOLISM IS INHIBITED LEADING TO INCREASED BLOOD LEVELS AND INCREASED CHANCES OF VENTRICULAR ARRHYTHMIAS.
ANTIBACTERIALS - CLARITHROMYCIN METABOLISM IS INHIBITED. RIFAMPICIN INCREASES ITS METABOLISM LEADING TO SUBCLINICAL LEVELS OF INDINAVIR. ERYTHROMYCIN LEVELS ARE TO BE REDUCED ONLY IF IT IS GIVEN IN VERY HIGH DOSES.
ANTIDEPRESSANTS - TRICYCLIC ANTIDEPRESSANTS METABOLISM IS INHIBITED BY HIV PROTEASE INHIBITORS.
ANTIEPILEPTICS - PHENOBARBITONE, PHENYTOIN, CARBAMAZEPINE INCREASE INDINAVIR METABOLISM LEADING TO REDUCED PLASMA LEVELS. CARBAMAZEPINE CONC. IS ALSO INCREASED.
ANTIFUNGALS - PLASMA CONC. OF HIV PROTEASE INHIBITORS IS INCREASED BY AZOLE ANTIFUNGALS LIKE FLUCONAZOLE ETC. CONVERSELY ANTIFUNGALS CONC IS INCREASED.
ANTIHISTAMINES - ASTEMIZOLE & TERFENADINE PLASMA CONC IS INCREASED TO TOXIC LEVELS.
ANTIPSYCHOTICS - PIMOZIDE & CLOZAPINE PLASMA CONC IS INCREASED TO TOXIC LEVELS.
CYCLOSPORIN - MUTUAL INCREASE IN PLASMA CONC IS SEEN WITH CONCURRENT USE.
ANTIVIRALS - HIV PROTEASE INHIBITORS CAN INHIBIT METABOLISM OF OTHER DRUGS OF THE SAME CLASS & INCREASE IN ADVERSE EFFECTS HAVE BEEN SEEN WITH SAQUINAVIR & RITONAVIR. SAME EFFECT IS SEEN WITH INDINAVIR & NELFINAVIR.
PLASMA CONC. OF INDINAVIR & SAQUINAVIR MAY BE REDUCED BY CONCURRENT USE OF NEVIRAPINE.
PLASMA CONC. OF INDINAVIR & SAQUINAVIR IS INCREASED BY DELAVIRDINE.
PLASMA CONC OF INDINAVIR & SAQUINAVIR IS DECREASED BY EFAVIRENZ.
PLASMA CONC OF NELFINAVIR IS INCREASED WHEN GIVEN WITH EFAVIRENZ.
DIDANOSINE SHOULD BE GIVEN 1 HR. APART FROM NELFINAVIR, INDINAVIR OR RITONAVIR DUE TO THE BUFFER INCLUDED IN DIDANOSINE FORMULATION WHICH INHIBIT HIV PROTEASE ABSORPTION.
CORTICOSTEROIDS - ESPECIALLY DEXAMETHASONE MAY INDUCE HIV PROTEASE METABOLISM WITH REDUCED PLASMA CONC.
ERGOT ALKALOIDS - PLASMA CONC IS INCREASED LEADING TO ERGOTISM.
INTERLEUKIN 2 - PLASMA CONC. OF INDINAVIR WERE INCREASED ON CONCURRENT USE.
HIV PROTEASE MAY INHIBIT THE METABOLISM OF TACROLIMUS, STATINS & WARFARIN. THEOPHYLLIN METABOLISM IN POTENTIATED LEADING TO REDUCED PLASMA LEVELS.