Ritonavir interaction with quinine is clinically insignificant but may warrant caution

Coadministration of ritonavir (100 mg twice daily) and quinine (105.3, 162, 210.6 or 648 mg single doses) was studied in 4 groups of HIV negative subjects (n=20 per group).

Quinine did not have a significant effect on ritonavir Tmax or Cmax, but increased AUC from 9.2 ± 2.21 ug.h/ml to 11.1 ± 3.96 ug.h/ml.

Similarly, ritonavir had no significant effect on quinine pharmacokinetics (Cmax 4.3 ± 1.07 vs 3.9 ± 0.88 ug/ml, AUC 78.9 ± 26.78 vs 68.4 ± 22.29 ug.h/ml, alone vs with ritonavir). Although the increased ritonavir exposure and decreased quinine exposure are unlikely to be of clinical significance, caution should be exercised if coadministered.

Wason S et al. Lack of clinically significant pharmacokinetic interactions between quinine and ritonavir in healthy adult participants. International Workshop on Comorbidities and Adverse Drug Reactions in HIV, Washington, July 2012. Abstract P21.