Metoclopramide treatment has been shown to augment milk production by stimulating prolactin secretion in women in whom lactational insufficiency develops after a full-term pregnancy. The effect of metoclopramide therapy in 23 women who were delivered of premature infants (birth weight 1,314 +/- 115 g, gestational age 30.4 +/- 0.7 weeks) and who were having difficulty maintaining milk production with milk expression was evaluated. Each woman had noted a gradual decrease in the total daily volume of expressed milk during the first several weeks of lactation. Maternal metoclopramide therapy was started at a mean of 32.0 +/- 3.7 days postpartum, after a review of diet and milk expression technique and an increase in the number of expressions per day failed to increase milk production. Daily milk production increased significantly from 93.3 +/- 18.0 mL/d to 197.4 +/- 32.3 mL/d between the first and seventh day of therapy. This increase was associated with significantly increased basal serum prolactin levels, from 18.1 +/- 3.3 ng/mL to 121.8 +/- 21.5 ng/mL. Although milk expression resulted in a variable increase in serum prolactin levels prior to metoclopramide treatment, milk expression did not produce any additional prolactin response in the treated women, with mean basal levels of 157.8 +/- 15.4 ng/mL v mean peak levels of 144.5 +/- 12.2 ng/mL. No major side effects were reported by the women, and no untoward effects were noted in the infants fed milk expressed while their mothers were being treated with metoclopramide.(ABSTRACT TRUNCATED AT 250 WORDS)