Allylestrenol

Allylestrenol has a fairly weak progestational effect on the human endometrium. In oestrogen-primed castrated women, getting a full secretory endometrium needed higher doses than those recommended for treating or preventing abortion. The same was true when menstruation was postponed (with an oestrogen added) in normal ovulating women.

In vitro studies showed that allylestrenol stimulates the synthesis of progesterone in the human placenta. It also brought about a significant (p/. 0,01) increase in the production of some specific placental enzymes, cystine aminopeptidase and heat-stable alkaline phosphatase.

In women with a normal pregnancy and in those with a threatened pregnancy, treatment with allylestrenol led to histological and histochemical changes that point to increased activity in the placenta, particularly in the syncytiotrophoblast. The effect on placental function was also suggested by higher levels of placental hormones (pregnanediol, oestriol, HCG and HPL) and enzymes (oxytocinase, CAP) in the maternal urine and plasma. These rises followed administration of the drug, for example in the early weeks as well as in the last trimester of pregnancy.

A study in full-term pregnant women found that allylestrenol in high doses (up to 100 mg daily) did suppress the intensity of spontaneous uterine contractions. It had no effect on how sensitive the uterine muscle is to oxytocin, and no adverse effect on the progress of normal delivery.

Studies in non-pregnant women, with and without endocrinological disorders, showed that allylestrenol has no oestrogenic or androgenic properties and no adverse effects on adrenal function.

Healthy non-pregnant female volunteers who were given allylestrenol showed no abnormal liver function tests and no water or salt retention.