Sex differences in use of potentially teratogenic disease modifying treatments for multiple sclerosis and degree of hormonal contraception overlap in women between 2007–2021: An Australian population-based study

Background: Disease modifying treatments (DMTs) for multiple sclerosis (MS) have varying levels of teratogenic potential, but whether this influences DMT prescribing patterns by sex or concurrent use of hormonal contraception in women is unknown. This study aimed to examine patterns in dispensing of DMTs in women and men with MS, and hormonal long-acting reversible contraceptive (LARC) overlap at DMT initiation among women. Methods: Population cohort study using 10% random sample of the Australian Pharmaceutical Benefits Scheme dispensing data (2007–2021). DMT dispensing data were evaluated separately for women and men aged 18–49 years. Hormonal LARC overlap was determined by receipt of contraceptive dispensing where the expected duration of efficacy overlapped with the DMT dispensing date. Results: DMTs with teratogenic potential (cladribine, sphingosine-1-phosphates and teriflunomide) were less likely to be commenced in women than men aged 18–39 (OR 0.70, 0.51–0.96), but not in those aged 40–49 (OR 0.93, 0.60–1.43). Hormonal LARC overlap was higher among those commenced DMTs with teratogenic potential compared with interferons (aOR 2.52, 1.14, 5.55). Conclusion: Sex and age differences in DMT utilisation were observed based on teratogenic potential. Hormonal LARC overlap appears higher in those receiving potentially teratogenic DMTs, but overall rates remain low.