Absorption of diazepam from the rectum and its effect on interictal spikes in the EEG.

Rectal administration of several different preparations of diazepam to a group of adult volunteer patients with epilepsy produced variable rates of absorption. Peak serum concentrations following 10 mg, 20 mg, and 30 mg of diazepam solution were achieved between 13-60 min, 10-120 min, and 30-90 min respectively. An experimental diazepam "solid solution" suppository was found to have significantly better absorption characteristics compared with the commercially available Valium suppository. Diazepam solution 20 mg was administered rectally in 10 adult epileptic patients with frequent spontaneous interictal spikes in their EEGs. A highly significant reduction in spike frequency was seen compared with placebo. The effect was most marked 10-20 min after administration of diazepam, when the mean spike count fell to 39 +/- 35 SD percent of the control value (p less than 0.01), and this corresponded with a mean serum diazepam level of 210 +2- 125 ng/ml.