Effect of parity on pituitary prolactin response to metoclopramide and domperidone: implications for the enhancement of lactation.

Objective: The gastrointestinal motility agents metoclopramide and domperidone are known to increase pituitary prolactin (PRL) secretion and breast milk production. This study compared the effect of single doses of two strengths of metoclopramide and a single dose of domperidone on PRL secretion.

Methods: Ten nonpregnant women had baseline evaluation of serum PRL concentrations. The PRL concentrations were then determined after random oral administration of metoclopramide 10 mg, metoclopramide 5 mg, and domperidone 10 mg. Blood samples were drawn in the first 7 days of the menstrual cycle, at 13 time points over a 6-hour period (0, 15, 30, 45, 60, 75, 90, 120, 150, 180, 240, 300, and 360 minutes), with the zero time point beginning at 0800 hours. Variables such as weight, height, age, gravidity, parity, and oral contraceptive use were recorded.

Results: Baseline PRL concentrations showed the natural circadian rhythm. Metoclopramide and domperidone both caused a significant increase in PRL. However, PRL secretion was most influenced by parity. Nulliparous women had the quickest and highest PRL secretion with metoclopramide 10 mg, compared with the PRL response with metoclopramide 5 mg and domperidone 10 mg. Conversely, multiparous women had PRL secretion patterns that were equivalent between the medications.

Conclusions: The PRL response to the medications was most influenced by parity. Therefore, we suggest that the medication therapy of choice for enhancing lactation may not be the same in all women, but may instead be determined by parity.