Absorption, distribution and excretion of [3H] octanoylprimaquine in rats

[3H]Octanoylprimaquine in castor oil and tea oil (6:4) was injected im into rats. The drug was absorbed slowly, maximum radioactivity was found after 3 d. About 12.3% of the dose was still remained at the im site after 30 d. The t1/2 = 8d in plasma and 12 d in liver. According to the residual amount in the im site, the plasma t1/2 was the t1/2 for absorption of the preparation, and the sustained effect was due to the slow absorption of the drug. The radioactivities were highest in plasma, then in kidneys, liver, spleen, lungs and heart. The rate of binding with plasma protein was 49%. In 30 d the total radioactivity excreted was 40% of the dose in urine and 38% in feces. No parent drug was isolated in the urine.