Diffusion of pyrimethamine from silicone rubber and flexible epoxy drug capsules

✍ Scribed by Fu, J. C. ;Kale, A. ;Moyer, D. L.

• Publisher: John Wiley and Sons
• Year: 1973
• Tongue: English
• Weight: 362 KB
• Volume: 7
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/jbm.820070207

✦ Synopsis

Abstract

The rate of diffusion of pyrimethamine, a pyrimidine‐based antimalarial drug, from silicone rubber is compared to the diffusion of this drug from a flexible epoxy. Specific amounts of drug were mixed into the epoxy resin prior to the addition of an aliphatic diamine curing agent in the reparation of the epoxy‐drug capsules and into the silicone rubber prior to vulcanization with stannous octoate in the preparation of silicone drug capsules. These capsules, in the form of discs, were separately immersed in water which was replenished at regular time intervals. The amount of drug released was determined spectrophotometrically (λ max = 275 mμ). Silicone rubber discs with 20 mg of drug incorporated/disc showed a much higher initial release rate than epoxy discs with an equivalent amount of drug incorporated. The rate of drug release is shown to be a nonlinear function of the amount of drug initially incorporated. The amine functional groups on pyrimethamine, and the possibility of its participation in the curing of the epoxy is noted. In silicone rubber, such interaction is not expected. The addition of a silica filler to the epoxy drug mixture is associated with greater uniformity in the observed drug release rates of capsules made from the same batch of polymer drug mixture. The Shore A durometer hardness of these drug capsules are 30 and 70 for silicone rubber and epoxy, respectively.