Temporal trends in clomiphene citrate use: a population-based study

To examine temporal trends in clomiphene citrate use and sociodemographic characteristics associated with treatment initiation and duration.

Retrospective cohort study.

British Columbia, Canada, 1996 to 2008.

Women aged 20 to 49 years.

None.

Temporal trends in treatment prevalence and incidence rates were assessed using Cochran-Armitage test for trend; differences in treatment duration were assessed using Wilcoxon and Kruskal-Wallis tests. Incidence rate ratios and 95% confidence intervals were estimated using Poisson regression.

A province-wide database of all dispensed prescriptions was used to identify clomiphene citrate users. Rural versus urban residence and neighborhood's socioeconomic quintile were identified based on postal codes. Overall, 26,993 women were prescribed clomiphene citrate between 1996 and 2008. Prevalence rates declined from 4.1 to 3.7 clomiphene users per 1,000 women during this period, while the incidence rates remained stable (2.2 new users per 1,000 women per year). Both prevalence and incidence rates declined among women aged 20 to 29 years, and showed a statistically significant increase among women aged 30 to 44 years. Women aged 30 to 34 years had the highest incidence of clomiphene use (4.5 per 1,000 women per year). Urban residence and low versus high socioeconomic status were associated with higher rates of treatment initiation. Older age (40 to 49 years) and urban residence were associated with shorter duration of use.

The increase in the incidence rates of clomiphene citrate use among women aged 30 to 44 years indicates a growing demand for fertility treatments in this population and may have contributed to the increase in multiple births.