Failure of commercially prepared isoniazid diet to produce isoniazid serum concentrations in rhesus monkeys.

A comparison was made of serum isoniazid concentrations and the time course of isoniazid elimination in rhesus monkeys given the drug im, orally on sugar cubes, or in a commercially medicated diet. When the drug was administered orally on sugar cubes or im, peak serum concentrations were usually reached within 2 hr. A threefold individual variation in the rate of elimination was noted, and in most animals the serum concentration at 6 hr approached zero. Isoniazid was not detected in the serum of any animal receiving the commercially medicated diet. Others using this medicated food in their tuberculosis prophylaxis programs should be aware that the diet probably does not provide therapeutically effective dosage to the animals.