The effect of methylxanthines on milk volume and composition, and growth of rat pups

A study was conducted to investigate the effect of differential dose levels of methylxanthines on lactational performance, with respect to milk volume and composition and pup growth. The methylxanthines; caffeine, theophylline and theobromine, were administered via drinking water in the proportions occurring in tea, at a dose of 50, 1 and 2 mg/kg body-weight respectively to Wistar albino rats throughout pregnancy and for up to the 14th day of lactation. A fourth group received a mixture of all three methylxanthines. Maternal food and fluid intake and weight changes, as well as weight gain in the litter were monitored thrice weekly. Milk samples were collected from the dams on days 7 and 14 of lactation, while milk volume was measured on days 12-13 by a method using tritiated water. Results showed that caffeine and theobromine significantly enhanced litter weight (P less than 0.01 and 0.05 respectively). In the caffeine group, enhanced litter growth was due to a significant increase (P less than 0.05) in milk volume, consequent to increased maternal food intake (P less than 0.05). In the theobromine group there was only a weak association between increased litter weight and milk volume. Theophylline had no effect on the volume or composition of milk, or litter weight. The combination of all three methylxanthines also failed to produce any of the positive effects observed with separate drug treatments.