Trough levels of the protease inhibitor Kaletra (lopinaivr boosted by ritonavir) are significantly higher in men with low body weight, according to a poster presentation at the Tenth Anniversary Conference of the British HIV Association (BHIVA) in Cardiff last week. The investigators, from Liverpool University Therapeutic Drug Monitoring Service, have called for further research to establish the clinical significance of their findings.
The Liverpool investigators performed a retrospective analysis of trough level samples (ten to 14 hours post dose) in adults receiving a twice daily 400mg dose of lopinavir. Plasma concentrations below 50ng/ml were excluded from analysis as they were likely to be the result of missed doses.
Data from 245 men and 49 women were studied. Individuals were stratified by gender and according to body weight (above or below 70kg). The investigators found that a greater proportion of males with low body weight had a trough level of lopinavir above 10,000ng/ml than men with a body weight above 70kg (17.2% versus 4.8%). However, the proportion of patients with trough concentrations of lopinavir below the therapeutic range did not differ significantly between the high and low weight individuals, and there were too few women in the study to determine if low body weight was associated with a higher trough level of the drug in women.
The investigators conclude that lopinavir levels appear to be affected by body weight and call for the clinical relevance of their findings to be explored in further studies.
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Gibbons S et al. Is there evidence for weight-adjusted dosing of Kaletra? Tenth Anniversary Conference of the British HIV Association, Cardiff, abstract P75, 2004.