E-DRUG: Norgestrel and combined contraceptive pills (cont'd)

[Barbara Mintzes <bmintzes@compuserve.com>]

E-drug: Norgestrel and combined contraceptive pills (cont'd)
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Dear E-druggers, 

I wanted to add a small note to the discussion on isomers and relative
contraceptive efficacy, as several people have mentioned that the form used
in Norplant, the subcutaneous delivery system, is much more effective in
preventing pregnancy than oral norgestrel-only contraceptives. I wanted to
suggest an additional simpler reason for the greater contraceptive
effectiveness: women using Norplant receive a higher daily dose of the
hormone, particularly during the first two years of use. This is also
intuitively unsurprising given the high rate of side effects experienced by
women using Norplant, particularly severe menstrual cycle disturbances.

Norplant capsules continuously release a daily dose of levonorgestrel
ranging from 85 micrograms/day just after implantation to 30 micrograms/
day at the end of the the five year period of contraceptive effectiveness.
This compares to a usual daily dose of 30 to 35 micrograms contained in
levonorgestrel-only pills.

I'm not sure if this adds much to the discussion on isomers except a note
of caution about directly interpreting differences in contraceptive
effectiveness as being related to the form of the hormone used in different
products.

With best regards,

Barbara Mintzes
bmintzes@compuserve.com
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