Pharmacological interventions for the induction of ovulation

Gonadotrophins in ovulation induction

For anovulatory women who fail to ovulate or conceive with clomiphene citrate, gonadotrophin ovulation induction has been the conventional second-line therapy. The aim of treatment is to achieve monofollicular development and ovulation. This differs fundamentally from the aim of ovarian stimulation for IVF, in which multiple follicular development is the goal. The small therapeutic window of ovulation induction requires a rigorous approach to monitoring, and willingness to cancel the cycle when multiple follicle development occurs. The two most widely used approaches are the low-dose step-up and the step-down protocols. While the latter more closely mimics the normo-ovulatory cycle, outcomes are similar. For safety reasons, the step-down protocol has not been widely adopted. The principle risks of ovulation induction are ovarian hyperstimulation syndrome and multiple pregnancy. There is a need to individualize treatment if outcomes are to be optimized. The role of adjuvant therapies remains unclear. However, prediction models based on initial screening parameters enable the optimal dose of FSH to be determined, and the identification of patients with a poor prognosis for successful treatment.

Potent inhibition of human cardiac potassium (HERG) channels by the anti-estrogen agent clomiphene—without QT interval prolongation

The acquired form of the long-QT syndrome (LQTS) is a major safety consideration for the development and subsequent use of both cardiac and non-cardiac drugs; it is usually associated with pharmacological inhibition of cardiac HERG-encoded potassium channels. Clomiphene is an anti-estrogen agent used extensively in the treatment of infertility and is not associated with a risk of QT interval prolongation, in contrast to a structurally related compound tamoxifen. We describe here a potent inhibitory effect (IC(50) = 0.18 microM) of clomiphene on HERG ionic current (I(HERG)) recorded from a mammalian cell line expressing HERG channels. Inhibition of I(HERG) by clomiphene showed voltage-dependence and developed quickly following membrane depolarisation, indicating contingency of block on HERG channel gating. At 100 nM, clomiphene and the related anti-estrogen tamoxifen produced similar levels of I(HERG) blockade (p > 0.05). Experiments on guinea-pig isolated perfused hearts revealed that, despite its inhibitory action on I(HERG), clomiphene produced no significant effect at 1 microM on uncorrected QT interval (p > 0.1) nor on rate-corrected QT interval (QT(c); p > 0.1 for QT(c) determined using Van de Water's formula). The disparity between clomiphene's potent I(HERG) inhibition and its lack of effect on the QT interval underscores the notion that I(HERG) pharmacology may best be used alongside other screening methods when investigating the QT-prolonging tendency and related cardiotoxicity of non-cardiac drugs.

Clomiphene citrate in the twenty-first century

Clomiphene citrate is the drug most commonly prescribed for ovulation induction. It is the first choice medication in normogonadotrophic oligo/amenorrhoeic infertility (WHO group 2), essentially associated with polycystic ovaries. Anovulatory women who are responsive to clomiphene citrate should be treated for at least six cycles and the treatment should probably be limited to a maximum of 12 cycles. It is necessary to monitor at least the first cycle with ultrasonography because of the risk of multiple pregnancy and the variable response of patients to different doses of clomiphene. In addition, the risk of ovarian hyperstimulation syndrome should not be underestimated. More triplets and higher order pregnancies result from ovulation induction than from in vitro fertilization, and multiple pregnancy has many risks for both mother and babies. The role of empirical clomiphene in the treatment of unexplained infertility is debatable and the present data are inconclusive. Obesity, hyperandrogenaemia and insulin resistance are important factors in clomiphene-resistant patients. Failure to ovulate in response to clomiphene has been approached by either medical or surgical treatment. An effective alternative medical treatment is gonadotrophin injections. Treatment with metformin and the new generation of insulin-sensitizing drugs is under evaluation. The most widely used surgical treatment today is laparoscopic ovarian drilling, which appears to be as effective as gonadotrophin therapy.

WITHDRAWN: Clomiphene citrate for ovulation induction in women with oligo-amenorrhoea

BACKGROUND

The administration of clomiphene citrate is followed by an enhanced release of pituitary gonadotropins resulting in follicular recruitment. After the drug is stopped, there is continuing secretion of estradiol, selection of the dominant follicle and, in successful cases, ovulation. Clomiphene is indicated as the initial treatment in the majority of women with amenorrhoea and oligomennorhoea. In women with irregular ovulation it seems to re-establish typical frequency of ovulation. Its effectiveness in oligo-amenorrhoeic women was tested in a number of randomised controlled trials at that time. These trials form the basis for the following review.

OBJECTIVES

Clomiphene citrate enhances the release of pituitary hormones, often resulting in ovulation. The objective of this review was to assess the effects of clomiphene citrate on ovulation and pregnancy in women with oligo-ovulatory subfertility.

SEARCH STRATEGY

The Cochrane Subfertility Review Group specialised register of controlled trials was searched.

SELECTION CRITERIA

Randomised trials of clomiphene compared with placebo or no treatment in women with oligo-ovulatory subfertility of at least 12 months duration.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed and data were extracted independently by two reviewers.

MAIN RESULTS

Four studies were included. They were all of crossover design. Since it was not possible to separate data from the first and second phases of these trials, the effect of clomiphene may be overestimated. Compared with placebo, clomiphene citrate was associated with increased ovulation. The odds ratio for high doses (50-250 milligrams per day) was 6.82 (95% confidence interval 3.92 to 11.85). This dropped to a non-significant odds ratio of 1.29 (95% confidence interval 0.48 to 3.49) with low doses (10 milligrams per day). Clomiphene citrate (all doses) was associated with an increased pregnancy rate per treatment cycle (odds ratio 3.41, 95% confidence interval 4.23 to 9.48).

AUTHORS' CONCLUSIONS

Clomiphene citrate (at doses between 50 to 250 milligrams per day) appears to be an effective method of inducing ovulation and improving fertility in oligo-ovulatory women. However adverse effects include possible ovarian cancer risk and risk of multiple pregnancy.

Inhibition of food-stimulated acid secretion (intragastric titration) by roxatidine acetate. Dose-response study

In 10 healthy male volunteers a dose-response study was carried out with roxatidine acetate, 75, 150, 300, and 600 mg, and placebo on food-stimulated gastric acid secretion (intragastric titration (IGT]. The design of the study, with drug intake 150 min before starting IGT, enabled stable inhibition over the 90-min observation period of the test. Cumulative secretory results showed a dose-related acid secretion inhibition (67% for 75 mg; 87.6% for 150 mg; 98.8% for 300 mg; 99.6% for 600 mg). The results were statistically significantly different from placebo and from each other, except for 300 mg versus 600 mg. With a Lineweaver-Burk plot, the ED50 was 41 mg and r = 0.98. Peak concentrations of roxatidine were observed either at T 150 or T 180. Significant correlation (r = 0.7; p less than 0.001) was obtained for the percentage inhibition with 75 mg and 150 mg together versus peak concentrations. Antisecretory potency with the IGT model applied to normal subjects appears to be of the same order for roxatidine acetate and for ranitidine.