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Trade names | Palmestril, Stilpalmitate |
Other names | Stilpalmitate |
Routes of administration | Intramuscular injection |
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Chemical and physical data | |
Formula | C50H80O4 |
Molar mass | 745.186 g·mol−1 |
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Diethylstilbestrol dipalmitate (brand names Palmestril, Stilpalmitate), also known as stilpalmitate, is a synthetic, nonsteroidal estrogen of the stilbestrol group and an ester of diethylstilbestrol (DES) that was formerly marketed but is now no longer available.[1][2] Its actions and uses are essentially the same as those of DES, but it is absorbed more slowly and for this reason has a much longer duration of action and improved tolerability in comparison.[3] A single 5 mg intramuscular injection of DES dipalmitate in oil solution has been found to have an average duration of action of 8 to 10 weeks[4] in terms of relief of menopausal symptoms, with a duration of as long as 15 to 16 weeks occurring in some women.[5][6][7] A single 15 or 20 mg intramuscular injection of DES dipalmitate in oil solution will control menopausal symptoms for 3 months or longer.[8] DES dipalmitate in aqueous suspension by intramuscular injection has been studied as well.[9]
A similar response is obtained with diethylstilbestrol. The free compound is less effective than diethylstilbestrol dipropionate which in turn is less effective than diethylstilbestrol dipalmitate. This is dramatically shown by our results which we have already reported, namely, that injections of diethylstilbestrol in dosages of 5 mg. once weekly for three weeks will give relief in the menopausal patient for an average of three weeks following cessation of treatment. A similar dosage of the dipropionate will induce a therapeutic effect for approximately five weeks under similar conditions while the dipalmitate has an effect lasting on the average of nine weeks and not uncommonly as long as 15 to 16 weeks.2
There is a possibility that some of the estrogens may be improved further so that even pellets may not be considered to possess advantages. In this regard, Freed and associates have introduced diethylstilbestrol dipalmitate.26 This combination of estrogen with a relative high fatty acid was injected in dosages containing 5 mg. of the active compound 3 times at weekly intervals. The period of relief from symptoms following cessation of therapy averaged 8 to 9 weeks. In some unpublished work the author has found that one injection of a 5 mg. dose in about 200 instances produced relief, on the average, for 5 weeks. It is obvious that compounds developed along these lines with, for instance, even higher fatty acid esters may be even more effective, or than an injection of 10 or 15 mg. will produce results equivalent to that of pellets.
Stilbestrol dipalmitate in oil is a soap-like material which can be liquified by heat and injected intramuscularly. A single injection containing 15 or 20 mg. of stilbestrol may control climacteric symptoms for three months or more at a time.