A comparative study on the clinical effects of rectal diazepam and pentobarbital on small children. Relationship between plasma level and effect.

In order to test the possible differences in the clinical effects between benzodiazepines and barbiturates, 5 mg of diazepam and 60 mg of pentobarbital were used in a double-blind study as rectal premedication in 75 small children before major surgery. There were no significant differences between the two groups in the six parameters tested (demeanour in the anaesthetic room, preoperative emetic effect, response to venepuncture, degree of salivary suppression, postoperative state in the recovery room, postoperative emetic effect). The concentrations of pentobarbital and diazepam (and its 3 active metabolites) in the plasma were determined by gas chromatography and correlated with the clinical effects. No significant correlation was found between the total active benzodiazepine concentrations and the clinical effects of rectal diazepam. In contrast to diazepam, a weak but significantly positive correlation between the plasma concentrations of pentobarbital and the total score was found. Similarly, the plasma level of pentobarbital and the response to venepuncture and the degree of salivary secretion were in correlation with each other. In the plasma concentrations of both pentobarbital and total benzodiazepines, a wide interindividual variation was observed, indicating irregular rectal drug absorption.