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Sustained-Release Hormonal Preparations XV: Release of Progesterone from Cholesterol Pellets In Vivo

1977; Elsevier BV; Volume: 66; Issue: 4 Linguagem: Inglês

10.1002/jps.2600660408

1520-6017

Angela Ann Joseph, Joel Hill, Jayvadan K. Patel, Sneha A Patel, Fred A. Kincl,

Steroid Chemistry and Biochemistry

Progesterone-sterol pellets were made that provided a zero-order release of progesterone for 80 days. 4-14C-Progesterone was used to measure the release in vitro and in vivo. The dissolution rate in vitro (distilled water as the desorbing medium) for progesterone-cholesterol (59:41 w/w) and progesterone-β-sitosterol (47:53 w/w) pellets was 72 μg/100 mm2/24 hr. The average in vivo absorption from subcutaneously implanted pellets in rabbits was 2±0.1 μg/ml of plasma/cm2 of surface area. Of this amount, 20-25% was progesterone; the remainder was progesterone metabolites and conjugates. Zero-order release (plasma levels) was obtained for approximately 80 days or until about 70% of the available progesterone was exhausted. During this time, the level of excreted radioactivity in urine continuously decreased, indicating that monitoring only this parameter would lead to erroneous conclusions. A long-term effect and increased effectiveness were obtained with a 5-20-mg progesterone equivalent dose, using gel prepared from 2% methylcellulose as the suspending medium.