Dydrogesterone

Medical Uses

Dydrogesterone has proven effective in the following conditions associated with progesterone deficiency:

Dydrogesterone has also been registered as hormone replacement therapy (HRT) to counter-check the negative effects of unopposed estrogen on the endometrium in women with an intact uterus.

Dysmenorrhea

Primary or essential dysmenorrhea is a very common gynaecological phenomenon experienced by women during their reproductive years. Clinical studies have shown symptom relief and a reduction in pain with dydrogesterone treatment for dysmenorrhea.

Secondary amenorrhoea

Secondary amenorrhoea is not a specific disease, but is instead a symptom. Dydrogesterone has been found to adequately induce bleeding within a sufficiently estrogen-primed endometrium. When estradiol levels are found to be low, dydrogesterone treatment is more effective when supplemented with estrogens.

Dysfunctional uterine bleeding and irregular cycles

Apart from a wide variety of medications in use to reduce heavy menstrual bleeding in patients with ovulatory cycles, oral progestogens like dydrogesterone have been found to be the most commonly prescribed as it has been found to prevent heavy bleeding.

Infertility due to luteal insufficiency

Oral dydrogesterone is effective drug, well tolerated and accepted among patients and can be considered for routine luteal support. Advantage of dydrogesterone is oral administration, easy to use and better patient compliance which results in high satisfaction score of oral dydrogesterone in luteal support of IVF/ICSI cycles. According to the Cochrane review 2011, there is clinical evidence in favor of dydrogesterone over micronized progesterone for luteal phase support. Dydrogesterone is used for luteal support in IVF protocols, for treatment of recurrent pregnancy loss.

Miscarriage

Threatened miscarriage is defined as bleeding during the first 20 weeks of pregnancy while the cervix is closed. It is the most common complication in pregnancy, occurring in 20% of all pregnancies. Recurrent abortion is defined as the loss of three or more consecutive pregnancies. Dydrogesterone is associated with approximately two-fold significant reduction in the miscarriage rate as compared to standard care in threatened and recurrent miscarriages with minimal side effects.

Endometriosis

Endometriosis is a chronic disease which can cause severe, progressive, and at times, incapacitating dysmenorrhoea, pelvic pain, dyspareunia and infertility. Dydrogesterone relieves pain without inhibiting ovulation, so that patients are able to become pregnant during treatment. Dydrogesterone is particularly suitable in cases where the woman desires to become pregnant and to prevent bleeding problems. Dydrogesterone results in statistically significant reductions in the symptoms pelvic pain, dysmenorrhea and dyspareunia after the first treatment cycle for the treatment of post-laparoscopic endometriosis. The amount and duration of menstrual bleeding is also significantly reduced, and from the end of the third month onwards, bleeding was considered normal in the majority of patients. Improvement of endometriosis was observed in 71% of patients and cure in 21%.

Premenstrual syndrome

Dydrogesterone has shown reasonable efficacy in relieving a number of premenstrual syndrome symptoms like mood swings & physical symptoms.

Hormone replacement therapy

The objective behind hormone replacement therapy is to actively increase the circulating levels of estrogen to control hot flushes and to prevent the long-term effects of the menopause, such as bone resorption and unfavourable changes in blood lipids. The administration of 17β-oestradiol halts, or reverses atrophic changes that occur due to the loss of endogenous oestradiol during the menopause.

Estrogen promotes endometrial cell growth and in postmenopausal women with an intact uterus, estrogen monotherapy results in continued endometrial development without the physiological secretory changes normally brought on by progesterone. This action is associated with an increased incidence of endometrial hyperplasia and carcinoma. Additional protection with progestogens is therefore important in patients with an intact uterus who receive estrogen replacement therapy. Dydrogesterone counters the proliferative effect of estrogens on the endometrium and ensures the transition to a secretory pattern and cyclical shedding of the endometrium in serial HRT regimes. Dydrogesterone effectively protects against the ontogenesis of endometrial hyperplasia. Unlike androgenic progestogens, dydrogesterone does not reverse the benefits brought on by 17β-oestradiol on lipid profiles and carbohydrate metabolism. In a continuous, combined HRT regimen, dydrogesterone retards the proliferation of the endometrium so that it remains atrophic or inactive.

Breast disorders

Cyclic treatment with low-dose (10 mg/day) dydrogesterone has been found to be effective in the treatment of fibrocystic breast changes and associated mastodynia (breast pain).

Pregnancy

Dydrogesterone has been prescribed and used in over 10 million pregnancies worldwide. There have been no harmful effects exhibited due to the use of dydrogesterone while pregnant. Dydrogesterone is safe to use during pregnancy only when prescribed and indicated by a medical practitioner.

Fertility

Studies have not shown any incidence of decreased fertility due to dydrogesterone at therapeutic dose.

Overdose

There is not enough clinical data to support overdose in humans. 360 mg is the maximum dose taken to date by humans and dydrogesterone was found to be well-tolerated at that oral dose. Additionally, there are no antidotes to overdose and subsequent treatments should be based on patient symptoms.

Toxicology

No severe or unforeseen toxicity have been accounted for with the use of dydrogesterone. In acute toxicity trials, the LD₅₀ doses in rats were in excess of 4,640 mg/kg orally.

The Ames test found no evidence of any potential mutagenic or toxicity properties.

Side effects

The most commonly reported drug related adverse reactions of patients treated with dydrogesterone without estrogen treatment in clinical trials of indications are migraines, headaches, nausea, menstrual disorders and breast pain/tenderness, bloating or weight gain.

The use of progestins, in particular medroxyprogesterone acetate, in treating post-menopausal symptoms have been associated with increased risk of blood clots and breast cancer in a study carried out by the Women's Health Initiative. While the study did not involve dydrogesterone, it is possible, but not certain, that it too increases these risks.

Interactions

In HRT, dydrogesterone is administered together with an estrogen. Therefore, the interaction between dydrogesterone and estrogens has been assessed, and no clinically significant interaction has been observed.

Pharmacology

Dydrogesterone is a highly selective progestogen, and due to its unique structure, unlike progesterone and many other progestins, binds almost exclusively to the PR. The affinity of dydrogesterone for the PR is relatively low at 15.9% of that of progesterone. However, in vivo, dydrogesterone is much more potent in comparison, with an equivalent dose, in terms of endometrial proliferation, that is 10 to 20 times lower than that of progesterone. This is due to pharmacokinetic differences between the two drugs, namely improved bioavailability and metabolic stability with dydrogesterone as well as additional progestogenic activity of its metabolites. Although dydrogesterone binds to both isoforms of the PR and has similar activity as an agonist of the PR_B as progesterone, its agonistic activity is weak in the case of the PR_A. Hence, dydrogesterone shows selectivity for PR_B activation. This could confer a therapeutic advantage, as the two receptor isoforms induce different physiological responses in target tissues.

Dydrogesterone does not bind to the androgen receptor, estrogen receptor, or glucocorticoid receptor. As such, it is devoid of androgenic, estrogenic, or glucocorticoid activity. Similarly to progesterone however, dydrogesterone binds to the mineralocorticoid receptor and possesses antimineralocorticoid activity, but only weakly so. Due to its activity as a progestogen, dydrogesterone can produce antigonadotropic effects. However, it does not suppress gonadotropin secretion or inhibit ovulation at typical clinical dosages. Unlike progesterone, which forms sedative neurosteroid metabolites, dydrogesterone is not able to be metabolized in a similar way due to structural differences, and for this reason, is non-sedative.

Effects and properties

When administered orally dydrogesterone has advantageous pharmacological properties compared to endogenous progesterone:

Dydrogesterone is characterised by progestational and PR-mediated antiestrogenic activity. This is demonstrated by its ability to induce a secretory transformation in the endometrium of immature or ovariectomised animals after they have been primed with estrogens (cf. the Clauberg test). The oral progestogenic potency of dydrogesterone is 20 times higher than that of progesterone. The progestational efficacy and potency of dydrogesterone was confirmed by standard test (i.e. delay of menses and induction of withdrawal bleeding). The benefits of estrogen or other target organs are not compromised by dydrogesterone.

Unlike many other synthetic progestogens, dydrogesterone is not chemically related to testosterone. Its low affinity for the androgen receptor explains why it has no unwanted androgenic effects even at high doses and after prolonged treatment showed:

Dydrogesterone is not converted into estrogen, and has no adverse estrogenic effects on fertility or sexual development.

At recommended doses, dydrogesterone has no effect on ovulation in healthy women:

These beneficial results are of particular relevance to the use of dydrogesterone in women who wish to become pregnant.

Absorption

Dydrogesterone has predictable pharmacokinetics. The single-dose kinetics are linear in the oral dose range of 2.5–10 mg. The pharmacokinetics do not change during repeated administration of up to 20 mg dydrogesterone once daily. Steady state is attained after 3 days of treatment.

Distribution

The plasma protein binding of dydrogesterone and 20α-DHD are unknown, but based on the plasma protein binding of other progestins, they are probably bound to albumin and not to sex hormone-binding globulin or corticosteroid-binding globulin.

Metabolism

Dydrogesterone is readily absorbed after oral administration. T_max values vary between 0.5 and 2.5 hours. Dydrogesterone is virtually completely metabolized, which occurs in the liver. The primary reaction (metabolic) is the hydrogenation of the 20-keto group mainly by AKR1C1 and to a lesser extent AKR1C3, resulting in 20α-dihydrodydrogesterone (20α-DHD), which is a potent progestogen similarly to dydrogesterone. The levels of 20α-DHD, which is the main active metabolite, are also found to peak about 1.5 hours post-dose.

After oral administration, it was found that plasma concentrations of 20α-DHD were substantially heightened than those of the primary drug. The ratios of 20α-DHD and dydrogesterone for AUC and C_max are in the order of 40 and 25, respectively. Absolute bioavailability is on average 28%.

All the metabolites of dydrogesterone retain the 4,6-diene-3-one structure, and are metabolically stable. As such, dydrogesterone does not undergo aromatisation, which is consistent with its absence of estrogenic effects. Furthermore, dydrogesterone does not undergo 17α-hydroxylation, which may contribute to its lack of androgenic effects.

The average terminal terminal half-lives of DHD and dydrogesterone vary between 14–17 and 5–7 hours, respectively.

Elimination

Dydrogesterone and its metabolites are excreted predominantly in urine. Total clearance of plasma is at a rate of 6.4 L/min. Within 72 hours, excretion is virtually complete. DHD is preponderantly present in the urine as a conjugate of glucuronic acid. Approximately 85% of the oral dose is successfully egested from the body within 24 hours.

Chemistry

Although its molecular structure is almost identical to that of natural progesterone, its unique design makes it a potent, orally active progestogen. In the dydrogesterone molecule, the hydrogen atom at carbon 9 is in the beta position and the methyl group at carbon 10 is in the alpha position - a reverse of the progesterone structure, hence the term 'retro' progesterone. Furthermore, it has a second double bond between carbon 6 and carbon 7 (the 4, 6-diene-3-one configuration). These small differences in chemical structure account for the improved oral activity, metabolic stability, and the lack of estrogenic, androgenic, glucocorticoid, and mineralocorticoid properties of dydrogesterone.

Sources

Dydrogesterone is manufactured by treating progesterone with ultra-violet light, leading to a change in the spatial structure. It is produced from the plant steroids, Dioscorea mexicana, a plant of the yam family native to Mexico. Dioscorea contains a sterol called diosgenin. Diosgenin is converted to progesterone.

History

Dydrogesterone is a steroidal progestin that was first synthesized by Duphar in the 1950s and was first introduced to the market in 1961. It is unique, being the only retrosteroid that is commercially available and its molecular structure is closely related to that of natural progesterone, but it has enhanced oral bioavailability.

It is estimated that during the period from 1977 to 2005 around 38 million women were treated with dydrogesterone and that fetuses were exposed to dydrogesterone in utero in more than 10 million pregnancies. It has been approved in more than 100 countries worldwide. It is commercially marketed under the brand name Duphaston and manufactured by Abbott (formerly known as Solvay Pharmaceuticals).

Dydrogesterone was first introduced, by Duphar, as Duphaston in the United Kingdom in 1961. Subsequently, it was introduced in the United States as Duphaston and Gynorest in 1962 and 1968, respectively. Duphaston was removed from the U.S. market in 1979, and Gynorest is also no longer available in the U.S..