Drug Interactions between emtricitabine / lopinavir / ritonavir / tenofovir and triazolam

CONTRAINDICATED: Coadministration with protease inhibitors (PIs) may significantly increase the plasma concentrations and pharmacologic effects of orally administered midazolam and triazolam. The mechanism is PI inhibition of intestinal and hepatic CYP450 3A4, the isoenzyme primarily responsible for the metabolic clearance of these benzodiazepines. Within the class, ritonavir is the most potent CYP450 3A4 inhibitor, while saquinavir is considered one of the weaker ones. In six healthy volunteers, ritonavir (200 mg twice a day for 2 days) nearly doubled the peak plasma concentration (Cmax) of triazolam (0.125 mg single dose) and increased its systemic exposure (AUC) and elimination half-life by 20- and 14-fold, respectively, compared to placebo. Ritonavir also decreased triazolam clearance to less than 4% of control values. In 12 healthy volunteers, the Cmax and AUC of oral midazolam (7.5 mg single dose) increased by more than 2- and 5-fold, respectively, during coadministration with saquinavir (soft gelatin capsule 1200 mg three times a day for 5 days) relative to placebo, while oral bioavailability increased from 41% to 90%. The AUC of intravenous midazolam (0.05 mg/kg single dose) increased 2.4-fold, and mean plasma clearance decreased by 56%. In both studies, the pharmacokinetic changes were accompanied by increased sedation and impairment of psychomotor performance.

MANAGEMENT: Given the potential for prolonged and/or increased sedation and respiratory depression associated with excessive benzodiazepine blood levels, concomitant use of oral midazolam or triazolam with protease inhibitors is considered contraindicated. Caution and close clinical monitoring are recommended when administering parenteral midazolam in combination with protease inhibitors. Appropriate medical management should be readily available in case of respiratory depression and/or prolonged sedation. Dosage adjustment for midazolam may be appropriate, especially if more than a single dose of midazolam is administered.

Switch to consumer interaction data

MONITOR: Coadministration with ritonavir, with or without lopinavir, has been suggested in postmarketing reports to increase the proximal tubular intracellular concentrations of tenofovir and potentiate the risk of tenofovir-induced nephrotoxicity. The proposed mechanism is ritonavir inhibition of tenofovir renal tubular secretion into the urine via multidrug resistance protein MRP2. Analysis of data from a compassionate access study in which 271 patients with advanced HIV disease received the combination for a mean duration of 63 weeks revealed no clinically significant nephrotoxicity associated with coadministration. However, there have been case reports of renal failure associated with acute tubular necrosis, Fanconi's syndrome, and nephrogenic diabetes insipidus in patients treated with tenofovir disoproxil fumarate in combination with ritonavir. Some patients had incomplete recovery of renal function more than a year after cessation of tenofovir therapy. Ritonavir given in combination with lopinavir has also been reported to modestly increase the plasma concentrations of tenofovir. In contrast, both slight decreases and no change in lopinavir and ritonavir concentrations have been reported.

MANAGEMENT: Caution is advised if tenofovir disoproxil fumarate is prescribed with ritonavir. Renal function should be monitored regularly, including surveillance for signs of tubulopathy such as glycosuria, acidosis, increases in serum creatinine level, electrolyte disturbances (e.g., hypokalemia, hypophosphatemia), and proteinuria. The same precaution may be applicable during therapy with other protease inhibitors based on their similar pharmacokinetic profile, although clinical data are lacking. Nelfinavir reportedly does not alter the pharmacokinetics of tenofovir, or vice versa. Tenofovir administration should be discontinued promptly if nephropathy develops.

Switch to consumer interaction data

MONITOR: Coadministration with ritonavir, with or without lopinavir, has been suggested in postmarketing reports to increase the proximal tubular intracellular concentrations of tenofovir and potentiate the risk of tenofovir-induced nephrotoxicity. The proposed mechanism is ritonavir inhibition of tenofovir renal tubular secretion into the urine via multidrug resistance protein MRP2. Analysis of data from a compassionate access study in which 271 patients with advanced HIV disease received the combination for a mean duration of 63 weeks revealed no clinically significant nephrotoxicity associated with coadministration. However, there have been case reports of renal failure associated with acute tubular necrosis, Fanconi's syndrome, and nephrogenic diabetes insipidus in patients treated with tenofovir disoproxil fumarate in combination with ritonavir. Some patients had incomplete recovery of renal function more than a year after cessation of tenofovir therapy. Ritonavir given in combination with lopinavir has also been reported to modestly increase the plasma concentrations of tenofovir. In contrast, both slight decreases and no change in lopinavir and ritonavir concentrations have been reported.

MANAGEMENT: Caution is advised if tenofovir disoproxil fumarate is prescribed with ritonavir. Renal function should be monitored regularly, including surveillance for signs of tubulopathy such as glycosuria, acidosis, increases in serum creatinine level, electrolyte disturbances (e.g., hypokalemia, hypophosphatemia), and proteinuria. The same precaution may be applicable during therapy with other protease inhibitors based on their similar pharmacokinetic profile, although clinical data are lacking. Nelfinavir reportedly does not alter the pharmacokinetics of tenofovir, or vice versa. Tenofovir administration should be discontinued promptly if nephropathy develops.

Switch to consumer interaction data