Development of an estriol-releasing intrauterine device

Interstitial delivery of dexamethasone in the brain for the reduction of peritumoral edema

Controlled-release polymers have facilitated the interstitial delivery of drugs within the central nervous system. In the present study, dexamethasone was incorporated into ethylene-vinyl acetate polymers, which were then implanted adjacent to a 9L gliosarcoma in the brain of Fischer 344 rats. The effect of interstitial delivery of dexamethasone on peritumoral edema was assessed and compared to the effect of dexamethasone delivered systemically. Eighty-five rats underwent intracranial implantation of the 9L gliosarcoma. Five days later, the animals were randomly assigned to one of four treatment groups: Group 1 received intracranial implantation of controlled-release polymers containing dexamethasone; Group 2 received intraperitoneal implantation of controlled-release polymers containing dexamethasone; Group 3 received serial intraperitoneal injections of dexamethasone; and Group 4 received sham treatment. The animals were sacrificed 3 days after initiation of therapy and their brains were removed for measurement of the water content (edema) in the tumor-bearing and contralateral hemispheres. Brain and plasma samples were analyzed by reverse-phase high-performance liquid chromatography to determine the tissue and plasma concentrations of dexamethasone. Measurement of the release kinetics of dexamethasone from the ethylene-vinyl acetate polymers in an in vitro system showed that the drug was released in a controlled, tapering fashion. During the first 3 days of controlled release in vitro, 330 micrograms of a total content of 7.5 mg of dexamethasone was released into the medium. Analysis of tissue for drug levels demonstrated, however, that the interstitial delivery of this fractional amount of dexamethasone within the brain resulted in levels 19 times higher than those achieved by administering the full dose of 7.5 mg systemically over a 3-day period. Conversely, the systemic administration of dexamethasone resulted in plasma levels 16 times higher than those measured in the interstitial delivery of dexamethasone in the brain. Brain-water content determinations showed that the interstitial controlled release of the fractional amount of dexamethasone within the brain was as effective in controlling peritumoral edema as systemic administration of the full dose by serial intraperitoneal injections. The study demonstrates the following: 1) controlled-release polymeric carriers deliver biologically active dexamethasone in a sustained fashion; 2) very high concentrations of dexamethasone in brain tissue can be achieved using interstitial polymer-mediated drug delivery while minimizing plasma concentrations of this drug which are sometimes associated with serious systemic side effects; and 3) peritumoral brain edema can be effectively treated by the interstitial delivery of dexamethasone directly within the tumor bed.

Effect of drug-vinyl copolymer delivery composites on the rat prostate

A radiation polymerized drug-vinyl copolymer delivery composite (0.8 mm in diameter, 3 mm long) was inserted into the right-lobe ventral prostate (I), into the right testis (II), and subcutaneously (III) into the back of male Wistar rats. The implantation was carried out over a period of 12 weeks maximum. From the relationship between the site of surgical insertion of the implant and the physiologic response (as measured by the decrease in the weight of the prostatic organs, e.g., ventral prostates, dorsolateral prostates, and seminal vesicles), it was found that in an AA560-containing composite (36 micrograms daily), the physiologic response is increased in order of (III) greater than (II) greater than (I). The same tendency was observed in the Estracyt-containing composite system (15 micrograms daily). The difference in the physiologic response owing to the site of surgical insertion of the implant was not observed in an E2-17 beta-containing composite (6 micrograms daily), although this composite showed the strongest physiologic response. No physiologic response in rats with CMA-containing composite (28 micrograms daily) was noted.

An intravaginal contraceptive device for the delivery of an acrosin and hyaluronidase inhibitor

A study was begun to develop a contraceptive delivery system that would free the user from precoital or daily administration and utilize a nonhormonal agent as the active ingredient. Testing of such a system in rabbits has led to the development of a device that will release a controlled level of an acrosin and hyaluronidase inhibitor into the vagina. This toroidal device is composed of a core of tetradecyl sodium sulfate (TDSS) incorporated in polyurethane surrounded by a rate-limiting membrane of polyurethane. Such devices had a sustained in vitro TDSS release rate of greater than or equal to 400 micrograms/day for over 30 days. These devices had a complete contraceptive effect in 15 rabbits bred weekly for 4 weeks. The contraceptive effect is due to release of the TDSS into the vagina and the subsequent binding of the TDSS to spermatozoa in the female reproductive tract. TDSS has a very low toxicity profile in the rat, dog, and rabbit.

Sustained drug delivery systems II: Factors affecting release rates from poly(epsilon-caprolactone) and related biodegradable polyesters

The release rates of several steroids from films and capsules of homopolymers and copolymer of epsilon-caprolactone, DL-lactic acid, and glycolic acid were measured in vitro and in vivo for up to 200 days. Relatively constant release rates from capsules (reservoir devices) were observed only under certain conditions. Factors that influence the drug release kinetics were evaluated. Release from poly(epsilon-caprolactone) and poly(epsilon-caprolactone-co-DL-lactic acid) was diffusion controlled. Release from poly(DL-lactic acid-co-glycolic acid) was associated with polymer degradation. Release from poly(DL-lactic acid) was very slow when diffusion controlled.