Objective

To characterize the antiviral effect and tolerability of higher dose (HD, 600 mg two times daily) and lower dose (LD, 400 mg two times daily) combination regimens of ritonavir and saquinavir in British Columbia (BC), Canada.

Design

Intent-to-treat analysis with suppression of plasma viral load to levels below 500 copies/ml as the main outcome measure.

Patients

Adult human immunodeficiency virus (HIV)-positive individuals in the province of British Columbia prescribed ritonavir and saquinavir in combination between 1 September 1996 and 30 June 1997, with a minimum of two plasma viral loads, one at baseline and one after the initiation of therapy.

Results

A total of 84 participants [27 HD (32%) and 57 LD (68%)] were prescribed ritonavir and saquinavir. There was no difference at baseline in the two groups with respect to age (P=0.466), CD4 cell count (P=0.373) and baseline plasma viral load (P=0.656). However, LD were more likely to have had prior protease experience than HD participants (65 versus 40%, P=0.037). The median follow-up time was 9 months. A total of 44 (52%) subjects demonstrated a decrease in plasma viral load to levels <500 copies/ml. After adjusting for length of follow-up, baseline CD4 cell count and prior AIDS diagnosis, HD participants were as likely to be suppressed to <500 copies/ml as LD individuals (P=0.760). HD participants did report more adverse effects (P=0.042) than LD subjects.

Conclusion

Our results provide confirmatory evidence that lower doses of ritonavir and saquinavir in combination are better tolerated and as effective as the standard doses of these drugs. This response, however, is seriously compromised by prior exposure to protease inhibitors.