الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Frogestin only contraceptive are being in orner to avoid the risks associated with the estrogens use in combined oral contraceptives. The effectiveness of progestin only contraceptives can be prolonged by incorporating them in a drug delivery system such as injectable solutions , vaginal rings , intrauterine devices, injectable microcapsules and implants • More than 25 years ago it was shown that polydimethylsiloxane (Silastic) could be used for the long term delivery of lipopr~lic drugs , and it was subsequently proposed for use in the delivery of contraceptive steroids. After studies with several steroids. t levonorgestrel was r selected as the drug with which the Silas tic subdermal implants would be developed further. The implantable contraceptive system available for use in family planning is the levonorgestrel Norplant implants. The Norplant implant system consists of six capsules , each containing 36 mg. of levonorgestrel and having a diameter of 2.4 mm and a length of 34 m. The six capsules a’ppear to release levonorgestrel at a rate of approximately 80 mcg per day during the first 6 18 months of use. This rate declines over the next few months and thereafter the capsules deliver approximately 30 mcg. of levonoTgestrel par. day. This latter rate of release is maintained for at least five years . The capsules. are inserted subdermally, in the inner aspect of the upper arm, by means of a specially designed lO-gauge trocar which is introduced through a single 2 -mm incision under local anaethesia.