arithromycin ↓ clarithromycin concentration
↑ 14-OH metabolite concentration Clinical significance unknown. In uninfected volunteers, 46% developed rash while receiving efavirenz and clarithromycin. No dose adjustment of ATRIPLA is recommended when given with clarithromycin. Alternatives to clarithromycin, such as azithromycin, should be considered. Other macrolide antibiotics, such as erythromycin, have not been studied in combination with ATRIPLA.
Antimycobacterial:
rifabutin ↓ rifabutin concentration Increase daily dose of rifabutin by 50%. Consider doubling the rifabutin dose in regimens where rifabutin is given 2 or 3 times a week.
Antimycobacterial:
rifampin ↓ efavirenz concentration If ATRIPLA is coadministered with rifampin to patients weighing 50 kg or more, an additional 200 mg/day of efavirenz is recommended.
Calcium channel blockers:
diltiazem ↓ diltiazem concentration
↓ desacetyl diltiazem concentration
↓ N-monodes-methyl diltiazem concentration Diltiazem dose adjustments should be guided by clinical response (refer to the full prescribing information for diltiazem). No dose adjustment of ATRIPLA is necessary when administered with diltiazem.
Others (e.g.,
felodipine, nicardipine,
nifedipine, verapamil) ↓ calcium channel blocker No data are available on the potential interactions of efavirenz with other calcium channel blockers that are substrates of CYP3A. The potential exists for reduction in plasma concentrations of the calcium channel blocker. Dose adjustments should be guided by clinical response (refer to the full prescribing information for the calcium channel blocker).
HMG-CoA reductase inhibitors:
atorvastatin
pravastatin
simvastatin ↓ atorvastatin concentration
↓ pravastatin concentration
↓ simvastatin concentration Plasma concentrations of atorvastatin, pravastatin, and simvastatin decreased with efavirenz. Consult the full prescribing information for the HMG-CoA reductase inhibitor for guidance on individualizing the dose.
Hormonal contraceptives:
Oral:
ethinyl
estradiol/norgestimate ↓ active metabolites of norgestimate A reliable method of barrier contraception must be used in addition to hormonal contraceptives. Efavirenz had no effect on ethinyl estradiol concentrations, but progestin levels (norelgestromin and levonorgestrel) were markedly decreased. No effect of ethinyl estradiol/norgestimate on efavirenz plasma concentrations was observed.
Implant:
etonogestrel ↓ etonogestrel A reliable method of barrier contraception must be used in addition to hormonal contraceptives. The interaction between etonogestrel and efavirenz has not been studied. Decreased exposure of etonogestrel may be expected. There have been postmarketing reports of contraceptive failure with etonogestrel in efavirenz-exposed patients.
Immunosuppressants:
cyclosporine,
tacrolimus, sirolimus,
and others
metabolized by
CYP3A ↓ immuno-suppressant Decreased exposure of the immunosuppressant may be expected due to CYP3A induction by efavirenz. These immunosuppressants are not anticipated to affect exposure of efavirenz. Dose adjustments of the immunosuppressant may be required |
