SHOULD NOT BE ADMINISTERED CONCURRENTLY WITH ASTEMIZOLE, CISAPRIDE, MIDAZOLAM, TRIAZOLAM, OR ERGOT DERIVATIVES BECAUSE COMPETITION FOR CYP3A4 BY EFAVIRENZ COULD RESULT IN INHIBITION OF METABOLISM OF THESE DRUGS AND CREATE THE POTENTIAL FOR SERIOUS AND/OR LIFE-THREATENING ADVERSE EVENTS (E.G., CARDIAC ARRHYTHMIAS, PROLONGED SEDATION OR RESPIRATORY DEPRESSION).ANTI-HIV PROTEASE INHIBITOR INDINAVIR (INCREASE DOSE FROM 800 MG TO 1000 MG EVERY 8 HOURS) PHENOBARBITAL, RIFAMPIN, RIFABUTIN) WOULD BE EXPECTED TO INCREASE THE CLEARANCE OF EFAVIRENZ RESULTING IN LOWERED PLASMA CONCENTRATIONS.CLARITHROMYCIN PLASMA CONCENTRATIONS DECREASED BY EFAVIR;