Effects of nirmatrelvir/ritonavir on midazolam and dabigatran pharmacokinetics in healthy participants

Abstract

AimsTo evaluate pharmacokinetics (PK) and safety after coadministration of nirmatrelvir/ritonavir or ritonavir alone with midazolam (a cytochrome P450 3A4 substrate) and dabigatran (a P‐glycoprotein substrate).MethodsPK was studied in 2 phase 1, open‐label, fixed‐sequence studies in healthy adults. Single oral doses of midazolam 2 mg (n = 12) or dabigatran 75 mg (n = 24) were administered alone and after steady state (i.e. ≥2 days) of nirmatrelvir/ritonavir 300 mg/100 mg and ritonavir 100 mg. Midazolam and dabigatran plasma concentrations and adverse events were analysed for each treatment.ResultsAfter administration of midazolam with nirmatrelvir/ritonavir (test) or alone (reference), midazolam geometric mean area under the concentration–time curve extrapolated to infinity (AUCinf) and maximum plasma concentration (Cmax) increased 14.3‐fold and 3.7‐fold, respectively. Midazolam coadministered with ritonavir (test) or alone (reference) resulted in 16.5‐fold and 3.9‐fold increases in midazolam geometric mean AUCinf and Cmax, respectively. After administration of dabigatran with nirmatrelvir/ritonavir (test) or alone (reference), dabigatran geometric mean AUCinf and Cmax increased 1.9‐fold and 2.3‐fold, respectively. Dabigatran coadministered with ritonavir (test) or alone (reference) resulted in a 1.7‐fold increase in dabigatran geometric mean AUCinf and Cmax. Midazolam or dabigatran exposures were generally comparable when coadministered with nirmatrelvir/ritonavir or ritonavir alone, with a slightly higher dabigatran Cmax with nirmatrelvir/ritonavir vs. ritonavir alone. Nirmatrelvir/ritonavir was generally safe when administered with or without midazolam or dabigatran. No serious or severe adverse events were reported.ConclusionCoadministration of midazolam or dabigatran with nirmatrelvir/ritonavir increased systemic exposure of midazolam or dabigatran. Midazolam exposures were comparable when coadministered with nirmatrelvir/ritonavir or ritonavir alone, suggesting no incremental effect of nirmatrelvir. Dabigatran Cmax was slightly higher when coadministered with nirmatrelvir/ritonavir compared with of ritonavir alone, suggesting a minor incremental effect of nirmatrelvir.