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Registry data reveal no major teratogenicity signal associated with sumatriptan use during pregnancy

Monday, November 23 2009 | Comments

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What's This? A new analysis of data from the Sumatriptan and Naratriptan Pregnancy Registry has not shown any signal for major teratogenicity associated with sumatriptan exposure during pregnancy. Although the authors of the analysis suggest that these findings offer some level of reassurance regarding the safety of in utero exposure to the drug, they caution that the registry size is too small to draw definitive conclusions or to evaluate the risk of specific defects.

The Sumatriptan and Naratriptan Pregnancy Registry allows health care professionals worldwide to report--on a voluntary basis--exposed pregnancies, with enrollment encouraged as early in pregnancy as possible (to facilitate prospective follow-up) and before any prenatal testing for birth defects is completed.

The registry obtains information about major birth defects (MBDs) that are external, recognizable in the delivery room or in prenatal ultrasound, and/or symptomatic shortly after birth. In the current analysis, the risk of MBDs with sumatriptan or naratriptan exposure was calculated as the number of infants and fetuses with MBDs divided by the number of infants/fetuses with MBDs plus the number of live births without defects.

During 12 years of monitoring, pregnancy outcome data were available for 558 infants and fetuses exposed in utero to sumatriptan, including 479 first-trimester exposures. There were 20 cases of MBDs following first-trimester exposure, yielding a risk of MBDs of 4.6% (95% CI, 2.9%-7.2%). There were 24 cases of MBDs following any in utero exposure, yielding an MBD risk of 4.7% (95% CI, 3.1%-7.0%).

There was no distinctive pattern of MBDs observed among infants exposed to sumatriptan, although the authors noted that 4 cases of ventricular septal defects among 433 live-born infants following first-trimester exposure is a finding that warrants further investigation.

The registry also included data for 55 infants and fetuses exposed to naratriptan, including 50 first-trimester exposures. Among these infants, there was 1 case of an MBD in a fetus following first-trimester exposure; this fetus was also exposed to sumatriptan.

The authors acknowledged certain limitations inherent in the pregnancy registry, including the lack of a control group, the voluntary nature of recruitment, the lack of standardized methods for ascertaining outcomes, and the low sensitivity for detecting MBDs that are not apparent shortly after birth or are not detectable by examining physicians with normal procedures.

Regardless, they suggested that these data complement results from preclinical studies and other observational investigations that failed to show a substantial increase in MBD risk following prenatal sumatriptan or naratriptan exposure. In addition, the investigators noted, the risk estimate calculated for sumatriptan falls below MBD risk estimates reported for known teratogens.

"While neither drug can unequivocally be designated as nonteratogenic on the basis of available data, the lack of a signal of major teratogenicity with sumatriptan across these several sources of data is encouraging," the researchers concluded. (Cunnington M, et al. Headache 2009;49:1414-1422.)

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