Final results from the 16-year sumatriptan, naratriptan, and treximet pregnancy registry

Objectives: To monitor for a signal of major teratogenicity by determining the risk of all birth major defects following in utero exposure to sumatriptan, naratriptan, and the sumatriptan/naproxen sodium combination product (tablets marketed in the United States as Treximet [GlaxoSmithKline, Research Triangle Park, NC, USA]), and to monitor for unusual patterns of defects that might suggest teratogenicity.

Background: The prevalence of migraine is highest in women of childbearing age. Coupled with the recurrent nature of migraine attacks and the high proportion of unplanned pregnancies, intentional and inadvertent exposure to anti-migraine drugs in pregnancy is likely. The Sumatriptan, Naratriptan, and Treximet Pregnancy Registry captured data on women exposed to those drugs during pregnancy to monitor for evidence of major teratogenicity.

Methods: In this primarily prospective, observational study, health care professionals from anywhere in the world enrolled, on a voluntary basis, women exposed to sumatriptan, naratriptan, or the sumatriptan/naproxen sodium combination product during their pregnancies. Only pregnancies with unknown outcomes at the time of enrollment were included in the analysis. The proportion of infants or fetuses with major birth defects was calculated as the total number of infants/fetuses with major birth defects divided by the sum of the number of infants/fetuses with major birth defects + the number of live births without defects. The risk of major birth defects was further stratified by earliest trimester of pregnancy exposure.

Results: The registry enrolled 680 evaluable exposed pregnant women, which resulted in 689 infants and fetuses (outcomes). Of these outcomes, 626 were exposed to sumatriptan, 57 were exposed to naratriptan (seven were exposed to both sumatriptan and naratriptan), and six were exposed to the sumatriptan/naproxen sodium combination product. Twenty outcomes with major birth defects were reported among 528 outcomes exposed in the first trimester to sumatriptan. The estimated risk of major birth defects following first-trimester sumatriptan exposure is 4.2% (20/478 [95% confidence interval [CI] 2.6%-6.5%]). Among 52 first-trimester exposures to naratriptan, major birth defects were reported in one outcome, an infant with exposure to both sumatriptan and naratriptan [birth defect risk of 2.2% (1/46 [95% CI 0.1%-13.0%]). No major defects were reported among the five outcomes with first-trimester exposure to the sumatriptan/naproxen sodium combination products.

Conclusions: The Sumatriptan, Naratriptan, and Treximet Pregnancy Registry detected no signal of teratogenicity associated with major birth defects for sumatriptan. This finding is consistent with results from other observational studies using a variety of control groups. Enrollment in the registry was insufficient to permit definitive conclusions of the risks associated with naratriptan or sumatriptan/naproxen sodium tablets, or to assess the risk of individual birth defects in any of the products studied. Low enrollment and high rates of loss to follow up within the registry over an extended period of time led the registry's scientific advisory committee to conclude that continuation of the registry beyond its 16 years would offer little additional power to rule out more moderate increases in the risk of birth defects. Data from the other ongoing surveillance sources constitute an important element of post-marketing surveillance of these medications. The lack of a signal of major teratogenicity with sumatriptan across these several sources of data is encouraging.