Pilocarpine reservoir systems

Figure 19 Exploded view of the pilocarpine Ocusert system (AJD) Transparent rate-controlling membranes. (B) Plastic ring, opaque white for visibUity in handling and insertion. (C) Drug reservoir. Total thickness of the assembled system is 0.3 mm. Major and minor axes of the ellipsoidal device are 13.4 and 5.7 mm, respectively.

Diffusion-controlled membranes exist in two categories depot systems, in which the drug is totally encapsulated within a reservoir, and monolithic systems, where the drug is dispersed in a rate-controlling polymer matrix [25]. One commercially successful depot device is the Alza Ocusert for ocular delivery of pilocarpine in the treatment of glaucoma [25]. 

Diffusional reservoir inserts consist of a core of drug surrounded by an inert rate-controlli polymeric barrier. A typical example of this system is the Ocuserx which delivers pilocarpine at a nearly zero-order rate for one week, and, being insoluble, necessitates removal from the conjunctival sac after exhaustion. 

The latter device, developed by Alza Corp., Palo Alto, California, is a diffusion unit consisting of a drug reservoir (e.g., pilocarpine HCl in an alginate gel) enclosed by two release-controlling membranes made of ethylene-vinyl acetate copolymer, and enclosed by a white ring which Slows positioning of the system in the eye. The Pilo-20 Ocular Therapeutic System has a release rate of 20 mg/hr for 7 days, and the Pilo-40 system a release rate of 40 mg/hr for 7 days. The former releases a total of 3.4 mg in 7 days, the latter 6.7 mg. In order to maintain constant release of tog, and in accordance with the principles of diffusion, there... 

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