Drug Interactions between Juluca and telithromycin

MONITOR: Telithromycin has the potential to prolong the QT interval of the electrocardiogram in some patients. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death. No cardiovascular morbidity or mortality attributable to QTc prolongation occurred with telithromycin treatment in 4780 patients during clinical trials, including 204 patients having a prolonged QTc at baseline. 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 drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Although the risk of a serious interaction is probably low, caution is recommended if telithromycin is used in combination with other drugs that can prolong the QT interval. Since the magnitude of QTc prolongation may increase with increasing plasma concentrations of telithromycin, the recommended dosage should not be exceeded, particularly in patients with renal or hepatic impairment. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.

Theoretically, coadministration with inhibitors of UGT1A or CYP450 3A4 isoenzymes may increase the plasma concentrations of dolutegravir, which is primarily metabolized by UGT1A1 with some contribution from CYP450 3A4. Dolutegravir is also a substrate of UGT1A3, UGT1A9, and P-glycoprotein in vitro. Potent CYP450 3A4 inhibitors such as boceprevir (800 mg every 8 hours) and telaprevir (750 mg every 8 hours) had no significant effects on the pharmacokinetics of dolutegravir given at 50 mg once daily. The interaction has not been studied or reported with UGT1A1 inhibitors such as nilotinib, regorafenib, and sorafenib. However, it is possible that simultaneous inhibition of UGT1A1 and CYP450 3A4 may lead to a clinically significant interaction with dolutegravir. In 12 study subjects, administration of dolutegravir (30 mg once daily) with the dual UGT1A1 and CYP450 3A4 inhibitor, atazanavir (400 mg once daily), increased dolutegravir peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Cmin; 24 hours postdose) by 50%, 91% and 180%, respectively, compared to administration without atazanavir. When the same dosage of dolutegravir was given with atazanavir/ritonavir 300 mg/100 mg once daily, the Cmax, AUC and Cmin of dolutegravir increased by 34%, 62% an 121%, respectively. Because safety data regarding increased dolutegravir exposures are limited, caution may be advisable if dolutegravir is used in combination with both a UGT1A1 inhibitor and a CYP450 3A4 inhibitor.