Allylestrenol, sold under the brand names Gestanin and Turinal among others, is a progestin medication which is used to treat recurrent and threatened miscarriage and to prevent premature labor in pregnant women.

[6] Allylestrenol is one of only a handful of progestogens that has commonly been used for such purposes, the others including progesterone, hydroxyprogesterone caproate, and dydrogesterone.

[8] The medication has also been studied in the treatment of gynecological disorders such as amenorrhea, irregular menstruation, and premenstrual syndrome.

[26] On the other hand, allylestrenol was found to be effective in the treatment of hot flashes in postmenopausal women.

[11][28][29][30][31][32][33][34][35][9][10][36][37][38][39][40][41][42][43] Related medications that have similarly been used to treat BPH, particularly in Japan, include chlormadinone acetate, gestonorone caproate, and oxendolone.

[46][47] In Japan, a 25 mg allylestrenol oral tablet, under the brand name Perselin, is marketed for the treatment of BPH.

Owing to its effect on the stomach lining, manufacturers recommend people with peptic ulcers, mild diabetes, or gastritis seek medical advice before using allylestrenol.

[48] Side effects of allylestrenol are few and have not been well-defined, but are assumed to be similar to those of related medications (i.e., other progestins).

[14] When used at high dosages in the treatment of BPH in men, allylestrenol can cause symptoms of hypogonadism and sexual dysfunction.

[15] It is lacking the keto group at the C3 position (part of the important 3-keto-4-ene structure) that is common in progestogens and is considered to be necessary for activity, and in relation to this, is thought to be a prodrug of 17α-allyl-19-nortestosterone (3-ketoallylestrenol).

[3] These findings may help to explain the absence of teratogenic effects of allylestrenol on the external genitalia of female and male rat fetuses.

[55][56][57] In accordance, the reduction of testosterone and luteinizing hormone levels with allylestrenol in men has been found in a study to be equivalent to that of chlormadinone acetate and oxendolone.

[33] However, another study found a significantly lower decrease in testosterone levels with 50 mg/day allylestrenol relative to 50 mg/day chlormadinone acetate of about 49–52% versus 76–85%, respectively.

[31][34][35] Allylestrenol therapy for BPH is associated with a significant decrease in prostate-specific antigen levels, which may mask the detection of prostate cancer.

[23][6][24][25][19] It has also been marketed under a variety of other brand names, including Alese, Alilestrenol, Allynol, Allytry, Alynol, Anin, Arandal, Astanol, Cobarenol, Crestanon, Elmolan, Fetugard, Foegard, Fulterm, Gestanin, Gestanin, Gestanol, Gestanyn, Gestin, Geston, Gestormone, Gestrenol, Gravida, Gravidin, Gravinol, Gravion, Gravynon, Gynerol, Gynonys, Iugr, Lestron, Loestrol, Maintane, Meieston, Moresafe, Nidagest, Orageston, Pelias, Preabor, Pregnolin, Pregtenol, Pregular, Prelab, Premaston, Prenolin, Prestrenol, Profar, Progeston, Protanon, and Shegest.

Allylestrenol has been marketed widely throughout the world, including in Europe, Southern, Eastern, and Southeastern Asia, Africa, Oceania, and Latin America.

[23][6][24][25] It appears to still be available in Bangladesh, the Czech Republic, Egypt, Hong Kong, India, Indonesia, Japan, Lithuania, Malaysia, the Philippines, Russia, Singapore, and Taiwan.

[23][6][24][25] Previously, allylestrenol has also been available in Australia, Austria, Belgium, Brazil, Germany, Greece, Hungary, Italy, Luxembourg, Mexico, Poland, South Africa, Spain, Sweden, Switzerland, Turkey, Ukraine, the United Kingdom, and Yugoslavia (now Serbia and Montenegro).