Polyanhydrides polymer—drug mixture

The reaction of castor oil with diisocyanates has been used to make polyurethanes.53 In one case, hydroxyethyl-methacrylate was included to form a prepolymer with a terminal methacrylate group that could be cured with benzoyl peroxide. Heating a mixture of ricinoleic, maleic, and se-bacic acids in a melt produced a polyanhydride with a molecular weight of over 100,000, which could be used as a biodegradable polymer for slow drug release.54... 

Biodegradable polymer blends of polyanhydrides and polyesters have been used as drug carriers [59], Polyflactic acid) (PLA), polyfhydroxybutyrate) (PHB), and poly(caprolactone) (PCL), of 2000 and 50000 molecular weights were mixed with poly(sebacic anhydride) (PSA), and the properties of these mixtures were studied. Mixtures of PHB and low molecular weight PLA or PCL formed uniform blends with various amounts of PSA. These blends possess different physical and mechanical properties compared to the parent polymers. The release rate of drugs from these polymeric blends increases with the increase in the content of the rapidly degrading component, PSA. 

This method was adopted to prepare polyanhydride copolymer of poly(bis(p-carboxy phenoxy) propane anhydride) with sebacic acid. In this method, the polymer is first melted and then mixed with solid particles of the drug. The mixture is suspended in a nomniscible solvent (e.g., silicone oil), continuously stirred, and heated to 5°C above the melting point of the polymer. Once the emnision is stabilized, it is cooled until the polymer particles solidify. The resniting microspheres are washed by decantation with petroleum ether. The primary objective for developing this method is to develop a microencapsulation process suitable for the water-labile polymers, for example, polyanhydrides. Microsphere with diameter of 1-1000 pm can be obtained, and the size distribution can be easily controlled by altering the stirring rate. 

---