Drug Interactions between eliglustat and Stribild

CONTRAINDICATED: Coadministration with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of eliglustat, which is primarily metabolized by CYP450 2D6 and, to a lesser extent, CYP450 3A4. Eliglustat at substantially elevated plasma concentrations is predicted to cause prolongation of the PR, QTc and QRS cardiac intervals, which may increase the risk of bradycardia, atrioventricular block, cardiac arrest, and serious ventricular arrhythmias such as torsade de pointes. In 31 subjects who were CYP450 2D6 extensive metabolizers (EMs), eliglustat peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 4.0- and 4.4-fold, respectively, following coadministration of eliglustat (84 mg twice daily) with the potent CYP450 3A4 inhibitor ketoconazole (400 mg once daily). Simulations using physiologically-based pharmacokinetic (PBPK) models suggest that ketoconazole may increase eliglustat Cmax by 4.4-fold and AUC by 5.4-fold in CYP450 2D6 intermediate metabolizers (IMs). PBPK modeling also suggest that ketoconazole may increase eliglustat Cmax by 4.3-fold and AUC by 6.2-fold in CYP450 2D6 poor metabolizers (PMs) given eliglustat 84 mg once daily (half the dosage used in EMs). The magnitude of interaction is expected to increase further with the addition of a CYP450 2D6 inhibitor like paroxetine. Simulations using PBPK models suggest that the combination of ketoconazole (400 mg once daily) and paroxetine (30 mg once daily) may increase eliglustat Cmax by 16.7-fold and AUC by 24.2-fold in EMs given eliglustat 84 mg twice daily. For IMs, the estimated increases in eliglustat Cmax and AUC are 7.5- and 9.8-fold, respectively.

MANAGEMENT: The use of eliglustat with a potent CYP450 3A4 inhibitor is considered contraindicated in CYP450 2D6 poor metabolizers (PMs) and intermediate metabolizers (IMs). The contraindication is extended to extensive metabolizers (EMs) when a moderate or potent CYP450 2D6 inhibitor is given concomitantly with a moderate or potent CYP450 3A4 inhibitor. In the absence of a concomitant CYP450 2D6 inhibitor, eliglustat may be prescribed at a reduced dosage of 84 mg once daily to EMs treated with a potent CYP450 3A4 inhibitor. Potent CYP450 3A4 inhibitors include itraconazole, ketoconazole, posaconazole, voriconazole, conivaptan, ceritinib, idelalisib, mibefradil, nefazodone, cobicistat, delavirdine, protease inhibitors, and ketolide and certain macrolide antibiotics. Potent and moderate CYP450 2D6 inhibitors include abiraterone, bupropion, celecoxib, cimetidine, cinacalcet, clobazam, darifenacin, diphenhydramine, dronedarone, duloxetine, flecainide, fluoxetine, methotrimeprazine, mirabegron, paroxetine, propafenone, propoxyphene, quinidine, ranolazine, sertraline, and terbinafine. Some drugs such as cobicistat, delavirdine, mibefradil, adagrasib and ritonavir are dual CYP450 3A4 and 2D6 inhibitors, and they should not be used with eliglustat in any patient regardless of their CYP450 2D6 metabolizer status. The product labeling for itraconazole states that concomitant use with eliglustat is contraindicated in CYP450 2D6 EMs taking a strong or moderate CYP450 2D6 inhibitor, CYP450 2D6 IMs and PMs during and for 2 weeks after treatment with itraconazole.

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MONITOR: Concomitant use of tenofovir with cobicistat may increase the risk for tenofovir-related renal adverse effects, including renal impairment, renal failure, elevated creatinine, and Fanconi syndrome. The mechanism of this interaction has not been described. Cobicistat may decrease estimated creatinine clearance via inhibition of tubular secretion of creatinine; however, renal glomerular function does not appear to be affected. When given concomitantly with cobicistat, the systemic exposure (AUC) and trough plasma concentrations (Cmin) of tenofovir was also increased by 23% and 55%, respectively. However, data are lacking to determine whether concomitant use of tenofovir with cobicistat-containing regimens is associated with a greater risk of renal complications compared with regimens that do not include cobicistat.

MANAGEMENT: Initiation of cobicistat or cobicistat-containing regimens is not recommended in patients with CrCl less than 70 mL/min if any coadministered medicine requires dose adjustment based on renal function (including tenofovir), or is nephrotoxic. If concomitant therapy is necessary, monitoring of renal function is recommended, particularly in patients with risk factors for renal impairment.

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GENERALLY AVOID: Cobicistat may increase the plasma concentrations of antiretroviral agents. The plasma concentrations of cobicistat may also be increased or reduced in the presence of antiretroviral agents. The proposed mechanism is cobicistat inhibition of the CYP450 3A4 isoenzyme, of which antiretroviral agents may be substrates, and the inhibition or induction of CYP450 3A4 by concomitant antiretroviral medications. Cobicistat is a mechanism-based inhibitor and substrate of CYP450 3A4 with no antiretroviral activity of its own. Rather, it is indicated in its capacity as a pharmacokinetic booster of CYP450 3A4 to increase the systemic exposure of some antiretroviral medications such as atazanavir, darunavir, and elvitegravir, which are substrates of this isoenzyme. Concomitant use of other antiretroviral agents with cobicistat may also increase the plasma levels and risk of side effects associated with these medicines. In contrast, concomitant use of cobicistat-boosted atazanavir or darunavir with CYP450 3A4 inducers nevirapine, etravirine, or efavirenz may reduce the plasma concentrations of cobicistat, darunavir, and atazanavir, leading to a potential loss of therapeutic effect and development of resistance to darunavir and atazanavir. Pharmacokinetic data are not available.

MANAGEMENT: Cobicistat is not intended for use with more than one antiretroviral medication that requires pharmacokinetic enhancement, such as two protease inhibitors or elvitegravir in combination with a protease inhibitor. In addition, cobicistat should not be used concomitantly with ritonavir due to their similar effects on CYP450 3A4. According to some authorities, use of the antiretroviral combinations of atazanavir-cobicistat or darunavir-cobicistat concomitantly with the CYP450 3A4 inducers efavirenz, etravirine, or nevirapine is also not recommended. Other authorities consider the administration of atazanavir-cobicistat with efavirenz or nevirapine to be contraindicated. Since dosing recommendations have only been established for a number of antiretroviral medications, product labeling and current antiretroviral treatment guidelines should be consulted.

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