Anal submucosal injection: a new route for drug administration in pelvic malignancies. Part I. Experimental study of misonidazole distribution in serum and tissues, with special reference to urinary bladder. Preliminary report.

The anal and oral administration routes were compared in 30 rats to study the distribution of misonidazole, a radiation sensitizer, in the serum and tissues with special reference to the urinary bladder. 14C-labelled misonidazole was administered in a dose of 0.2 ml water/100 gm body weight containing 1 mu Ci misonidazole. The dose was given orally by stomach tube in 15 rats, and was injected in the submucosa of the anal canal in another 15. Animals were then killed after 15, 30, 60, or 120 minutes or after 24 hours. Organs were dissected, and radioactivity was determined in each by the internal standard method. The study has shown that the highest drug concentration in the bladder tissue relative to the serum was achieved with the anal submucosal route. Its level was eight and five times that of the serum 15 and 30 minutes after administration, respectively, in contrast to the oral route in which the drug concentration was one-quarter and equal to the serum level at the same time intervals. The anal route would thus provide the adequate channel required for misonidazole to promote radiation responsiveness in bladder carcinoma.