Objective:

Previous research in healthy volunteers has demonstrated that rifampicin and adjusted doses of lopinavir/ritonavir soft-gel capsules resulted in adequate exposure to lopinavir. Our objective was to study the combined use of rifampicin and the newly introduced lopinavir/ritonavir tablets.

Methods:

A total of 40 healthy volunteers were planned to start with 600 mg rifampicin once daily from days 1–5. From days 6–15, volunteers were randomized to receive lopinavir/ritonavir tablets dosed as either 600/150 or 800/200 mg twice daily, both in addition to 600 mg rifampicin once daily. A 12 h pharmacokinetic curve was planned on day 15. Safety assessments were conducted regularly throughout the study period.

Results:

Eleven volunteers started as the first group in this study. No major complaints occurred during day 1–5 (rifampicin only). After addition of lopinavir/ritonavir, eight volunteers suffered from both nausea and vomiting, one from nausea only, and one from vomiting only. On day 7, increases in aspartate aminotransferase/alanine aminotransferase (AST/ALT) levels were reported in all volunteers and on day 8, the study was prematurely terminated. The AST/ALT levels continued to rise and peaked (grade 2, n= 2; grade 3, n= 1; grade 4, n= 8) on days 9–10. All values returned to normal within 6 weeks.

Conclusions:

The study showed a high incidence of adverse events when a higher than standard dose of the new lopinavir/ritonavir tablets was combined with rifampicin. In the future, this drug combination should not be given to healthy volunteers. Liver function should be carefully monitored when rifampicin and lopinavir/ritonavir are combined in patients.