- Patients who are taking HIV Antiretrovirals: (indinavir, nelfinavir, ritonavir saquinavir); Antibiotics: (clairithromycin, itraconazole, ketoconazole, telithromycin,fluconazole, erythromycin); Calcium Channel Blockers (verapamil, diltiazem),Amiodarone, Ciprofloxacin. (These drugs inhibit CYP 3A4 enzyme which metabolises ketamine)