title: Progesterone-releasing vaginal rings for use in postpartum contraception. I. In vitro release rates of progesterone from core-loaded rings.
abstract: Vaginal rings of Dow Corning 382 Silastic polymer, having identical outside dimensions, were fabricated to contain cores of different diameters loaded with 25% w/w progesterone. Elution of rings was carried out in continuously flowing baths of isotonic saline at 37 degrees C and quantities of progesterone released in 24 h periods measured for up to 128 days. Release of the steroid was shown to be a membrane diffusion-controlled process, modified by the development of a gradually increasing zone of depletion at the core surface. Rings of a suitable core diameter were selected to give initial release of 5 mg/24 h progesterone and sterile batches of these rings, prepared for WHO-sponsored clinical studies in post-partum, lactating women, were shown to give highly consistent and reproducible rates of in vitro drug delivery. A comparison was made with the in vitro release rates of rings containing a homogeneous dispersion of progesterone.
authors.affiliation: Chemistry Department, City University, London, U.K.
authors.forename: S A
authors.initials: SA
authors.lastname: Matlin
authors.forename: A
authors.initials: A
authors.lastname: Belenguer
authors.forename: P E
authors.initials: PE
authors.lastname: Hall
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003274:Contraceptive Devices, Female; D066298:In Vitro Techniques; D008962:Models, Theoretical; D011374:Progesterone; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D011374:Progesterone