Secretion of nizatidine into human breast milk after single and multiple doses.

Disposition of the H2-receptor antagonist nizatidine was studied in serum, urine, and breast milk. Five lactating women and five nonlactating women participated; the disposition of nizatidine was studied in three of the lactating women. Single and multiple doses of 150 mg nizatidine were administered orally. The disposition of nizatidine (half-life, 1 1/2 hours; apparent serum clearance, 40 L/hr; renal clearance, 27 L/hr; and apparent volume of distribution, 1.4 L/kg) was similar in lactating and nonlactating women. These pharmacokinetic results were analogous to observations for men in other studies. Nizatidine breast milk concentrations were directly proportional to corresponding serum concentrations. On average, 96 micrograms nizatidine, less than 0.1% of the maternal dose, was secreted into milk during a 12-hour interval after either single or multiple doses.