Sustained concentrations of active compound were maintained in vitro and in vivo for an oral and a parenteral dosage form respectively. The vehicle of a oral dosage form was modified and the molecular structure of a parenteral dosage form was modified. An oral dosage form was tested in vitro using dissolution apparatus. A parenteral dosage form was tested in vivo using rats. A new oral suspension dosage form for acetylsalicylic acid was compared to two controlled release forms and two immediate release dosage forms which are currently commercially available. A parenteral thrombomodulin analogue conjugated to polyethylene glycol was compared to the unconjugated thrombomodulin analogue. In each case the goal was to maintain sustained concentrations of active compound. / Graduation date: 1991