Introduction
A synthetic steroid with progestational activity.
Uses
Allylestrenol is a steroid used to prevent premature labour in pregnant women.
Allylestrenol was designed to be used for miscarriage prevention, prevention of premature labour and has been investigated for possible use in men for treatment for benign prostatic hyperplasia.
Associated Conditions
Pharmacodynamics
Allylestrenol is a progestogen structurally related to progesterone that has been given in threatened and recurrent miscarriage, and to prevent premature labour. However, with the exception of proven progesterone deficiency, such use is no longer recommended. In threatened miscarriage in progesterone-deficient women a suggested dose is 5 mg three times daily by mouth for 5 to 7 days.
Mechanism of Action
Allylestrenol is similar in structure and function to progesterone. Progesterone shares the pharmacological actions of the progestins. Progesterone binds to the progesterone and estrogen receptors. Target cells include the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. Once bound to the receptor, progestins like Progesterone will slow the frequency of release of gonadotropin releasing hormone (GnRH) from the hypothalamus and blunt the pre-ovulatory LH (luteinizing hormone) surge. In women who have adequate endogenous estrogen, progesterone transforms a proliferative endometrium into a secretory one. Progesterone is essential for the development of decidual tissue and is necessary to increase endometrial receptivity for implantation of an embryo. Once an embryo has been implanted, progesterone acts to maintain the pregnancy. Progesterone also stimulates the growth of mammary alveolar tissue and relaxes uterine smooth muscle. It has little estrogenic and androgenic activity.
Route of Elimination
The glucuronide and sulfate conjugates of pregnanediol and pregnanolone are excreted in the urine and bile. Progesterone metabolites which are excreted in the bile may undergo enterohepatic recycling or may be excreted in the feces. Progesterone metabolites are excreted mainly by the kidneys.
Dosage
Threatened abortion: 1 tablet three times daily until symptoms disappear.
Habitual abortion: 1-2 tablets daily as soon as pregnancy is diagnosed. The administration should be continued for at least one month after the end of the critical period.
Threatened premature delivery: Dosage must be determined individually. High dosages (up to 40 mg daily) have been used.
In case of a missed dose, it should be taken as soon as the patient remembers & she should continue the regular dosing schedule. A double dose is not recommended.
