Tissue distribution of [14C]ethambutol in mice.

Fifteen male mice were given oral doses of 32 mg [14C]ethambutol/kg in a study of the tissue distribution of the drug. Animals were killed 1, 2, 4, 7, and 24 h after dosage and radioactivity in various tissues was measured. Peak concentrations were seen at 2 h after dosage. With the exception of brain, all tissues examined (liver, kidney, heart, spleen, lung, and muscle) developed tissue-to-plasma concentration ratios greater than 2. Highest values were seen in liver, kidney, and lung. High lung values were viewed as a favorable attribute for a drug used in the treatment of tuberculosis.