The effect of repeated-dose activated charcoal on the pharmacokinetics of sodium valproate in healthy volunteers

Aims We investigated the effects of repeated-dose charcoal administered several hours after sodium valproate on the pharmacokinetics of a single dose of the drug in healthy volunteers. Methods The pharmacokinetics of sodium valproate were studied in seven healthy volunteers after administration of a syrup (300 mg) on two occasions, one of which was followed by administration of repeated doses of oral charcoal starting 4 h after the drug up to 32 h (total dose 80 g). Results Valproate was rapidly absorbed with maximum concentrations Ih after administration. The area under the plasma concentration-time curve to 48 h (AUG (0,48 h)) was 408 +/- 114.5 (s.d.) mg l(-1) h in the control phase and 398 +/- 108.6 mg l(-1) h after charcoal and the t(1/2) elimination was 20 +/- 6.8 h in the control phase, and 22 +/- 9.2 h after charcoal (NS). Conclusions Repeated-dose activated charcoal does not appear to enhance the rate of elimination of sodium valproate after therapeutic doses of the drug and any beneficial effect of charcoal in overdose may be to prevent absorption of valproate still present in the gut.