A poster at the 48th ICAAC conference held in Washington in October reported an interaction between buprenorphine/naloxone and the protease inhibitor tipranavir that was not overcome by ritonavir boosting.

This was a multiple dose, open-label, sequential, non-randomised study in HIV negative subjects stabilised on at least 3 weeks of BUP/NAL therapy.

At day 7 of concomitant administration, buprenorphine AUC and C24h were not affected by co-administered TPV/r (<6% change relative to BUP/NAL alone) while Cmax decreased approximately 14%. However, although AUC, Cmax and C24h of norbuprenorphine, the major BUP metabolite, were decreased almost 80% and naloxone AUC and Cmax were decreased approximately 44% and 36%, respectively, when coadministered with TPV/r, there was no clinical evidence of opioid withdrawal and no need to modify buprenorphine dose.

Compared to historical controls AUC and C12h tipranavir levels decreased by 26% and 39%, respectively and Cmax was unchanged. Ritonavir C12h was similar, but Cmax and AUC were lower in by 40-50% and 35%, respectively.

The authors concluded that no modification of BUP/NAL is required but that caution should be used when combining BUP/NAL with tipranavir/r due to sgnificantly decreased tipranavir plasma concentrations.

Ref:
Bruce R et al. Pharmacokinetic Interactions between Buprenorphine/Naloxone & Tipranavir/Ritonavir in HIV-Negative Subjects Chronically Receiving Buprenorphine/Naloxone. 48th ICAAC. Poster abstract A-967a.