PMID: 6106671Jun 1, 1980Paper

Long-term controlled delivery of levonorgestrel in rats by means of small biodegradable cylinders

The Journal of Pharmacy and Pharmacology
D L WiseH J Esber

Abstract

Hormone release rates from biodegradable cylindrical implants consisting of a physical matrix of [14C]levonorgestrel and copolymers of [3H]lactic and glycolic acids have been monitored in rats. Two copolymers were evaluated: one consisted of 90 parts L-lactide/10 parts glycolide (90L/10G) containing 33 or 50% hormone by weight, and the other of 50 parts DL-lactide/50 parts L-lactide (50DL/50L) containing 50% hormone. For each system, 4-6 rods (0.8 x 16 mm) providing 19 mg of steroid per rat were subcutaneously implanted into the scapular regions of 5 rats, and 14C and 3H in faeces and urine were determined weekly for 90-724 days. An initial burst of hormone release, peaking at approximately 90 microgram day-1, occurred in the first two weeks. This was followed by an approximately 10-30 microgram day-1 for the 90L/10G system containing 33% hormone, a more uniform rate of approximately 25 microgram day-1 for the 50DL/50L system and the highest rate of approximately 40 microgram day-1 for the 90L/10G system containing 50% hormone. 3H and 14C in residual implants of 90L/10G with 33% hormone removed from animals dying of natural causes during the test were assayed. For this system 3H activity decreased by over 50% within 250 days, c...Continue Reading

References

Nov 1, 1978·The Journal of Pharmacy and Pharmacology·D L WiseJ F Howes
Apr 1, 1979·The Journal of Pharmacy and Pharmacology·D L WiseG J McCormick
Dec 15, 1975·Life Sciences·A D SchwopeJ F Howes
Mar 1, 1976·Contraception·L C AndersonJ F Howes

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Citations

Aug 12, 2009·Journal of Materials Science. Materials in Medicine·G J S DawesJ Duszczyk
Nov 1, 1990·Biomaterials·H T WangE Schmitt
Oct 1, 1990·Biomaterials·R H MüllerP Couvreur
Nov 5, 1998·Journal of Controlled Release : Official Journal of the Controlled Release Society·M MiyajimaM Ikeda
Sep 9, 1999·Journal of Controlled Release : Official Journal of the Controlled Release Society·M MiyajimaM Ikeda
Jul 30, 1999·Journal of Controlled Release : Official Journal of the Controlled Release Society·M MiyajimaM Ikeda
Apr 1, 1984·Journal of Microencapsulation·V VidmarI Jalsenjak

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