Nevirapine daily exposure for daily 400 mg dose compared to 200 mg twice-daily

When administered to HIV-infected patients, a daily 400-mg dose of nevirapine gives an equivalent daily exposure as a 200 mg twice-daily dose does, according to researchers in the Netherlands. Dr Rolf P. G. van Heeswijk, from Slotervaart Hospital, in Amsterdam, and colleagues randomized 20 HIV-infected patients already using nevirapine to either continue receiving the drug at 200 mg twice a day or to switch to a 400-mg dose once a day.

After 2 weeks, the researchers measured the steady-state plasma pharmacokinetics of nevirapine over a 24-hour period. Patients were then switched to the other dosing regimen for 2 weeks, after which the researchers again evaluated the pharmacokinetics of the drug. As assessed by the area under the plasma concentration versus time curve, nevirapine exposure was similar between the 2 dosing regimens, Dr van Heeswijk’s group reports in the May 26th issue of AIDS. Other pharmacokinetic parameters such as the time to maximal plasma concentration, plasma elimination half-life, apparent oral clearance, and apparent volume of distribution also did not significantly differ between the 2 regimens.

However, the investigators note that the maximal plasma concentration was higher, and the minimal plasma concentration was lower, with the once-daily regimen compared with the twice-daily regimen. ‘The clinical implications of these differences remain to be established,’ the authors write, noting that ‘thus far, no relationship between (maximum) plasma nevirapine concentrations and toxicity has been discerned.’

The results of this study demonstrate that the daily exposure to nevirapine is not significantly different between a dosing regimen of 400 mg once daily and 200 mg twice daily,’ they conclude.

Comment

This report correctly states that no relationship has been established between maximum Nevirapine concentrations and toxicity. Caution should be observed, however, as there has been a relationship established between minimal plasma concentration (Cmin or trough) of nevirapine and virological response. Lower trough levels were observed with once daily dosing.