There was no increase in the risk of birth defects among women who received clarithromycin in early pregnancy.
SUNDAY, Jan. 6, 2013 (MedPage Today) —
In a large cohort study, women who took the drug in the first trimester were 56 percent more likely to miscarry than those who did not take the drug, according to Jon Traerup Andersen, MD, of Denmark's Copenhagen University Hospital, and colleagues.
Reassuringly, there was no increase in the risk of birth defects, Andersen and colleagues reported online in PLOS ONE.
The drug has been associated with both miscarriage and birth defects in animal studies, and for that reason is not recommended for use by pregnant women, the researchers noted.
But since many pregnancies are unplanned and the drug is widely used, a "substantial number" of women might be at risk, they argued, although data are limited on the extent of that risk.
To help pin down the matter, they looked at 931,504 pregnancies in Denmark — registered between Jan. 1, 1997 and March 31, 2007 — including 705,837 live births, 77,553 miscarriages, and 148,114 induced abortions.
Using a national prescription database that is 97.5 percent complete, they identified 401 women who were prescribed clarithromycin during the first trimester of their pregnancy.
Among those women, 40 — or 10 percent — miscarried, compared with 77,513, or 8.3 percent, in the unexposed group, they reported. Those numbers yielded an adjusted hazard ratio for miscarriage of 1.56, with a 95 percent confidence interval from 1.14 to 2.13.
There were 253 live births among the women exposed to clarithromycin and 9 (3.6 percent) were diagnosed with a major malformation, compared with 24,808 (3.5 percent) among children born to unexposed mothers. The difference was not significant.
When clarithromycin use in the first trimester was compared directly with other drugs, the hazard ratios were similar to that seen in the main analysis — about a 45 percent to 69 percent increase in risk.
The findings "strengthen other data" on the risks of clarithromycin, Andersen and colleagues concluded.
But they cautioned that they lacked information on why clarithromycin was prescribed, so it remains possible that the underlying disease, in some cases, led to the miscarriage rather than the drug itself.
There is no data on prescribed dosages, they noted, and while they have information showing that the exposed women bought and paid for their prescriptions, there is no proof that they actually took the drug.
It is also possible, Andersen and colleagues cautioned, that women getting the drug differed from unexposed women in ways that were "causally related to the outcome," such as obesity, alcohol consumption, smoking and antiphospholipid syndrome.
Finally, they noted, registry data is subject to misclassification and the rate of miscarriage might have been under-reported.
Thursday, August 20, 2020