Drug interactions between Crixivan and Norvir
| Results for the following 2 drugs: |
|---|
| Crixivan (indinavir) |
| Norvir (ritonavir) |
Interactions between your selected drugs
ritonavir ↔ indinavir
Applies to:Norvir (ritonavir) and Crixivan (indinavir)
ADJUST DOSE: Coadministration with ritonavir may significantly increase the plasma concentrations of indinavir. The mechanism is ritonavir inhibition of indinavir metabolism via CYP450 3A4. In a study with healthy volunteers, ritonavir (200 mg to 400 mg every 12 hours) increased the peak plasma concentration (Cmax) and systemic exposure (AUC) of indinavir by up to 110% and 475%, respectively, compared to administration of indinavir alone. However, increasing ritonavir dosage did not yield proportional increases in indinavir Cmax and AUC. Ritonavir reduced intersubject variability in indinavir plasma levels and has also been shown to eliminate food effects on the bioavailability of indinavir. Indinavir had negligible effect on the pharmacokinetics of ritonavir.
MANAGEMENT: Based on the magnitude of interaction, indinavir dosage should be reduced when coadministered with ritonavir. A regimen of (indinavir:ritonavir) 400:400 mg twice a day with food has been well tolerated in clinical trials and is recommended by some HIV experts. This dosing reportedly produces comparable indinavir AUC as standard indinavir (i.e., unboosted indinavir 800 mg three times a day) but increases plasma trough levels by 4-fold and reduces Cmax by over 50%, which may enhance dosing convenience as well as the safety-to-efficacy profile of indinavir. Lower doses of ritonavir (100 to 200 mg) plus 800 mg of indinavir twice daily with food are also recommended by HIV experts. These regimens appear to be equally effective as standard indinavir but may be somewhat less well tolerated, as indicated by an increased rate of treatment discontinuation and adverse effects such as nephrolithiasis, taste disturbances, and gastrointestinal intolerance in some studies. One trial also found that ritonavir-boosted indinavir (800:100 mg twice daily) had poorer tolerability and caused greater plasma lipid increases than ritonavir-boosted saquinavir (1000:100 mg twice daily), although virologic responses were similar. Limited data suggest that once-daily regimens with indinavir 1200 mg and ritonavir 200 to 400 mg may also be efficacious and warrant further investigation.
See also...
Drug Interaction Classification
The classifications below are a guideline only. The relevance of a particular drug interaction to a specific patient is difficult to determine using this tool alone given the large number of variables that may apply.
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
Do not stop taking any medications without consulting your healthcare provider.
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