Abstract
Phenobarbital was released fastest from Witepsol H15 suppository among four Witepsol bases tested. A coprecipitate of phenobarbital and povidone (ratio, 1 : 3) gave an X-ray diffraction pattern which indicates that the drug is in an amorphous form in the coprecipitate, and the dissolution and permeation patterns of the drug from the coprecipitate indicated that drug dissolution from the coprecipitate was rapid. Release of the drug from a Witepsol H15 suppository containing the coprecipitate was faster than that from Witepsol H15 containing the drug alone or containing a physical mixture of the two components. Administration of the suppository containing the coprecipitate also gave the highest blood levels of the drug.
