Norvir Tablets and Sustiva

In the database of official manuals used in the service creation an interaction registered by statistical results of studies was found, which can either lead to negative consequences for the patient health or strengthen a mutual positive effect. A doctor should be consulted to address the issue of joint drug administration.

Using ritonavir together with efavirenz may alter the effects of ritonavir. Contact your doctor if you experience dizziness, nausea, or tingling or numbness in your extremities. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

MONITOR: Coadministration with efavirenz may variably affect the plasma concentrations of ritonavir. Specifically, ritonavir levels have been reported to increase when it is given therapeutically as an antiretroviral agent and decrease when it is used at low dosages as a pharmacokinetic booster. In 11 healthy subjects given ritonavir 500 mg every 12 hours, efavirenz (600 mg once a day) increased the mean peak plasma concentration (Cmax) and systemic exposure (AUC) of ritonavir by 24% and 18%, respectively. Efavirenz Cmax and AUC also increased 14% and 21%, respectively. The combination was associated with a higher frequency of adverse effects and laboratory abnormalities. In contrast, addition of efavirenz in 14 healthy male volunteers given indinavir 800 mg and ritonavir 100 mg orally twice a day led to decreases of 34%, 36% and 39% in ritonavir Cmax, AUC, and trough plasma concentration (Cmin), respectively. Efavirenz is primarily an inducer but also can be an inhibitor of the CYP450 3A4 isoenzyme. At low ritonavir plasma levels, efavirenz induction appears to be the predominant effect and causes an overall increased clearance of ritonavir. At higher plasma levels, however, ritonavir inhibiting effects may take over, resulting in increased concentrations of the drugs. However, efavirenz reportedly had no effect on the pharmacokinetics of ritonavir administered as lopinavir-ritonavir (400 mg-100 mg twice daily).

MANAGEMENT: When ritonavir is given therapeutically, coadministration with efavirenz may be associated with a higher frequency of adverse clinical events (e.g., dizziness, nausea, paresthesia) and laboratory abnormalities (elevated liver enzymes). Monitoring of liver enzymes is recommended during combination use. When ritonavir is given as a pharmacokinetic booster, limited data suggest it may be possible to overcome the inducing effects of efavirenz by increasing the ritonavir dosage (e.g., 200 mg twice a day).

Norvir Tablets

Generic Name: ritonavir

Brand name: Norvir, Norvir Soft Gelatin

Synonyms: Ritonavir

What is Norvir Tablets?

Sustiva

Generic Name: efavirenz

Brand name: Sustiva

Synonyms: n.a.

What is Sustiva?