Follow-up measurements of Nevirapine plasma levels over a prolonged period.

Over a period of more than four years of treatment, 177 Nevirapine plasma levels were taken from 27 patients. The values showed a high inter-patient variability and a lower intra-patient variability. Differences in body weight turned out to be the main reason for inter-patient variability. Treatment over a prolonged period did not result in any change in plasma concentrations. Adjusting dosage by means of therapeutic drug monitoring would appear to be a reasonable way of maximising patient benefit from treatment.