Microspheres of propranolol HCI were successfully prepared using cellulose acetate butyrate (CAB) polymer by emulsion solvent evaporation technique. The effect of drug:  polymer ratio on the produced microspheres particle size, drug encapsulation efficiency and drug release properties were evaluated Conventional suppositories containing free drug and sustained release (SR) suppositories containing microspheres of propranolol HCI were formulated with hydrophilic polyethylene glycol (PEG) and lipophilic Witepsol H 15 bases. Increase in drug content and particle size were observed with an increase in drug: polymer ratio. In vitro release studies were  performed in phosphate buffer (pH 7 4). Results have shown that drug release from microspheres was affected by drug: polymer ratio. When the polymer: drug ratio was increased, the release of the drug was highly decreased. Witepsol base showed higher release rates of the dug compared with PEG base from conventional suppositories .On the other hand, slower release rates were obtained by dispersing microspheres of the drug into suppositories and also, Witepsol suppositories showed higher rates of drug release compared to PEG suppositories.
This study suggested that incorporation of propranolol HCI microspheres into a lipophilic or hydrophilic suppository base can give SR properties for the drug which is promising as being more useful than conventional formulations in therapy.