Serum concentration of clonazepam after rectal administration.

The purpose of the present study was to evaluate the absorption of clonazepam administered rectally. 10 adult non-epileptics were given 0.02 mg clonazepam/kg body weight, and blood samples were drawn 0, 2, 5, 7, 10, 15, 30 and 60 min after administration. The concentrations were measured by gas-chromatography. To gain an impression of the serum concentration after intravenous administration, 2 persons were given 1 mg clonazepam and blood samples were drawn and analyzed in the same way as after rectal administration. Peak values occurred 10 to 30 min after rectal administration; the values were between 18 and 57 nmol/l. After intravenous administration, the values were very high within the first 10-15 min; hereafter the concentrations were about the same level as the peak values after rectal administration, indicating that clonazepam is well-absorbed after rectal administration and can be used in the treatment of status epilepticus, possibly in larger doses than those used in this study.