Changes in the plasma diazepam concentration and its anticonvulsant effect after the discharge of a diazepam suppository from the rectum in rats

Abstract

One of the clinical problems regarding the use of suppositories for patients is the discharge of the medication itself after the insertion of the suppository. The effects of the discharge of diazepam (DZP) suppositories from the rectum on the plasma DZP concentration and its anticonvulsant action were investigated in rats. The plasma DZP concentration reached a maximum at approx. 30 min after the rectal administration of a 5 mg/kg DZP suppository. The discharge of the DZP suppository from the rectum at 5 or 10 min after rectal administration significantly reduced the plasma DZP concentration and the anticonvulsant action of the DZP suppository against pentylenetetrazol-induced seizures. However, when the suppository was discharged from the rectum after 20 min, the plasma DZP concentration and the anticonvulsant action were only slightly but not significantly decreased. These results suggest that the discharge of the DZP suppository in the early phase, within 20 min, decreases the plasma concentration and the anticonvulsant action of the DZP suppository in rats. Therefore, when the suppository is discharged from the rectum immediately, sufficient observation and proper treatment are necessary.