The national impact of ritodrine hydrochloride for inhibition of preterm labor.

Ritodrine hydrochloride is a beta 2-receptor agonist that relaxes uterine smooth muscle. It was developed specifically for treatment of preterm labor and was approved for this indication in 1980 by the Food and Drug Administration. Estimates of ritodrine usage in the United States were calculated based upon annual sales, and these were examined in relation to the incidence of births in 500-g weight categories less than 2500 g. We estimate that more than 100,000 women with preterm labor are treated with ritodrine annually, but this has had minimal if any impact on the incidence of low birth weight in this country.