Ketoconazole is inferior to ritonavir as an alternative booster for saquinavir in a once daily regimen in Thai HIV-1 infected patients

A model-based pharmacokinetic assessment of drug-drug interaction between tacrolimus and nirmatrelvir/ritonavir in a kidney transplant patient with COVID-19

We experienced a patient with a remarkable and prolonged increase in tacrolimus blood concentrations when nirmatrelvir/ritonavir was concomitantly used. The inhibitory intensity and duration of nirmatrelvir/ritonavir on tacrolimus pharmacokinetics were examined using a model-based analysis. A renal transplant patient taking oral tacrolimus continuously was treated with nirmatrelvir/ritonavir for 5 days. The baseline tacrolimus trough blood concentration was 4.2 ng/mL. Tacrolimus was discontinued on Day 6 after the concomitant administration of nirmatrelvir/ritonavir, and the trough concentration increased to 96.4 ng/mL on Day 7. The model-based analysis showed that tacrolimus clearance decreased to 35% and bioavailability increased by 18.7-fold after the coadministration of nirmatrelvir/ritonavir, compared with before the coadministration. Therefore, nirmatrelvir/ritonavir drastically decreased both the apparent clearance and apparent volume of distribution. Simulated tacrolimus concentrations could be best fitted to the observed concentrations when the inhibitory effects of nirmatrelvir/ritonavir were modeled to disappear over about 10 days by first-order elimination. In conclusion, nirmatrelvir/ritonavir greatly increases tacrolimus concentrations by not only reducing clearance, but also increasing bioavailability. Interactions between nirmatrelvir/ritonavir and low-bioavailability drugs which are substrates for CYP3A and P-glycoprotein, such as tacrolimus, are harmful, and concomitant use of these medicines should be avoided.

Protease inhibitor therapy in resource-limited settings

PURPOSE OF REVIEW

The use of protease inhibitors in resource-limited settings will increase in coming years as HIV treatment cohorts mature. We review data available to guide the expanded use of protease inhibitors in these settings.

RECENT FINDINGS

The safety and effectiveness of protease inhibitors may be affected by the context of their use, yet limited data exist regarding the use of these agents in resource-limited settings in either first or subsequent regimens. Critically, data are needed regarding optimal regimens at time of first-line nonnucleoside reverse transcriptase inhibitor-based regimen failure. A number of alternative strategies are being investigated, including dual-boosting, monotherapy and dose reduction. Despite recent progress cost, storage requirements, drug interactions and formulation continue to hinder the use of protease inhibitors, particularly for children.

SUMMARY

Protease inhibitors are the core component of second-line therapy in resource-limited settings and are used in specific situations in first-line therapy. Use of second-line regimens has been more diverse than first line, but WHO has recently prioritized regimens containing lopinavir/ritonavir or ritonavir-boosted atazanavir. As use of protease inhibitors in resource-limited settings increases evidence needs to be accrued to guide further expanded use.

How much ritonavir is needed to boost protease inhibitors? Systematic review of 17 dose-ranging pharmacokinetic trials

BACKGROUND

Ritonavir has been evaluated at boosting doses of 50–800 mg daily with seven protease inhibitors: amprenavir, atazanavir, darunavir, indinavir, lopinavir,saquinavir and tipranavir. Minimizing the boosting dose of ritonavir could improve tolerability and lower costs.

METHODS

A MEDLINE search identified 17 phamacokinetic trials using different ritonavir doses with protease inhibitors. The dose of ritonavir used was correlated with plasma levels of each boosted protease inhibitor. For the five pharmacokinetic trials of lopinavir/ritonavir, a meta-analysis was used to estimate the effects of lopinavir dose versus ritonavir dose on lopinavir pharmacokinetics.

RESULTS

Saquinavir, fosamprenavir and darunavir were boosted equally well by lower(50–100 mg) versus higher doses of ritonavir. Indinavir, tipranavir and lopinavir were boosted more by higher ritonavir doses. Data on atazanavir were inconclusive. The ritonavir dose-dependence of boosting effects did not correlate with their bioavailability or their effects on ritonavir plasma levels. Atazanavir and indinavir raised plasma ritonavir levels by 69–72%, whereas saquinavir had no effects on ritonavir. Darunavir,lopinavir, tipranavir and fosamprenavir all lowered ritonavir plasma levels. For the meta-analysis of lopinavir/ritonavir trials, the 200/150 mg twice daily (b.i.d.) dose of lopinavir/ritonavir (one Meltrex 200/50mg tablet and one ritonavir 100mg b.i.d.)showed lopinavir area under the curve and minimum concentration similar to the standard 400/100mg b.i.d. dose.

CONCLUSION

It may be possible to use three protease inhibitors (saquinavir, amprenavir and darunavir) with lower doses of ritonavir. A 200/150 mg b.i.d. dose of lopinavir/ritonavir could lower costs while maintaining very similar lopinavir plasma levels to the standard dose. New pharmaco enhancer drugs may need to be used at different doses to boost different antiretrovirals.