Contraception with subdermal ST-1435 capsules: side-effects, endocrine profiles and liver function related to different lengths of capsules.

One Silastic capsule of 15 mm, 20 mm or 30 mm length was inserted subcutaneously into the ventral aspect of the left forearm or upper arm of 28 healthy women during menstrual bleeding or not later than on the seventh day of the menstrual cycle. A new capsule of the same length was inserted after six months and both capsules were removed twelve months after the first insertion. Side-effects, including changes in body weight, blood pressure, menstrual bleeding and liver function test results, were registered. Blood samples were taken from selected subjects twice a week during the 1st, 2nd, 3rd, 6th, 7th and 12th month of use. Plasma concentrations of ST-1435 were measured by radioimmunoassay and the effects of treatment on pituitary and ovarian function were determined by assaying plasma concentrations of LH, FSH, estradiol and progesterone. There were no differences in hormonal side-effects between subjects who had a 30 mm capsule or subjects who had 20 mm or 15 mm capsules, but subjects who had 20 or 15 mm capsules had significantly longer bleeding or spotting periods in comparison with subjects who had a 30 mm capsule. There were no changes in blood pressure, body weight or liver function test results in comparison with pre-insertion values. The plasma level of ST-1435 was not significantly higher during the use of 30 mm capsules than during the use of 20 or 15 mm capsules. During the use of the shorter ST-1435 capsules, plasma estradiol elevation and slightly suppressed FSH were seen, while the use of longer capsules resulted in a slight suppression of LH. Progesterone concentrations during monitored cycles indicated anovulation. No pregnancies occurred during the study period of one year. The continuation rate at one year was 71% in the 30 mm capsule group and 57% in the 20 and 15 mm capsule groups taken together.