I was taught that methyldopa is labeled “Cat. B” for pregnancy and beta blockers and calcium channel blockers are “Cat. C,” but you consider these classes safe (Item 106-4). Please explain.
—Norman Zellers, MSPAS, PA-C, Carson City, Nev.

Category B means that there is no evidence of risk in humans: Either animal findings show risk (but human findings do not), or if no adequate human studies have been done, animal findings are negative. Category C means that risk cannot be ruled out; human studies are lacking and animal studies are either positive for fetal risk or lacking as well. However, potential benefits may justify the potential risk.

Of course, no drug can ever be considered perfectly safe in pregnancy, and therefore, risk must be balanced with benefit. Many experts warn against treating mild hypertension in pregnant women, especially if it is not associated with pre-eclampsia. On the other hand, severe hypertension can be lethal if untreated, leading to such obstetric disasters as placental abruption, hemorrhage, and fetal demise.

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Methyldopa has been used for years and is considered safe (Am J Kidney Dis. 1991;17:149-153). Whether beta-adrenergic blockers are safe in pregnancy is more controversial. Lower birth weights have been reported, but these are hard to interpret because maternal hypertension—the reason the women were treated—is also a major cause of small-for-gestational-age babies (Cochrane Database Syst Rev. 2007;[1]:CD002252). Thus, beta blockers may not be first-line, but they might be acceptable in a gravida with high BP who cannot tolerate or has not been adequately controlled with other classes of medication.

Calcium channel blockers are considered safe and acceptable (Cochrane Database Syst Rev 2003;[3]:CD002863).
—Reuben W. Zimmerman, PA-C (110-21)