Drug Interactions between emtricitabine / lopinavir / ritonavir / tenofovir and Pavagen TD

MONITOR CLOSELY: Intracoronary administration of papaverine has been associated with QT interval prolongation and torsade de pointes (TdP) arrhythmia. The risk may theoretically increase in patients receiving concomitant medications that can also prolong the QT interval or cause bradycardia. QT interval prolongation has not been reported following systemic or intracavernosal administration of papaverine. The precise mechanism of papaverine-induced ventricular tachyarrhythmias has not been delineated, but may involve inhibition of potassium currents and prolongation of the action potential duration. In a study involving 182 consecutive patients undergoing fractional flow reserve measurements, premature ventricular beats occurred in 15.9% of patients following administration of intracoronary papaverine. TdP occurred in 2.8% of patients, and of those, 1.7% developed ventricular fibrillation. The incidence of intracoronary papaverine-induced ventricular tachyarrhythmias has not been determined, but has ranged between <0.67% and 8.8% following intracoronary administration of 6 mg to 20 mg. Based on numerous reports, female gender, hypokalemia, alkalosis, bradycardia, administration of papaverine into the left coronary artery, and a prior history of drug-induced QT prolongation may be risk factors for papaverine-induced fatal ventricular tachyarrhythmias. Apart from isolated case reports, there are no published data regarding the potential interaction between intracoronary papaverine and its use with other QT-prolonging drugs. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). In addition, the extent of drug-induced QT prolongation is dependent on the particular drugs involved and dosages of the drugs.

MANAGEMENT: Caution and close monitoring are advised during intracoronary administration of papaverine, particularly in patients receiving concomitant drugs that can prolong the QT interval or cause bradycardia and in patients with other risk factors described above. Some QT prolonging medications have specific monitoring, dosing, and/or other recommendations present in their labeling to help mitigate or monitor this side effect; therefore, it may be advisable to consult the package labeling of the concomitant medication if coadministration with intracoronary papaverine is being considered or deemed necessary.

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