Intratunical versus parenteral administration of methotrexate.

Methotrexate (MXT) distribution in serum, testicle and epididymis after administration into the tunica vaginalis cavity or intravenously was studied in 36 dogs. The dogs were divided into two equal groups: (1) an intratunical group in which 20 mg MXT solution was injected into the tunica vaginalis sac of each dog and (2) a parenteral group in which the same MXT dose was administered intravenously. The MXT concentration in serum, testicle and epididymis was determined 2, 4 and 24 h after MXT administration. Clinical and histologic examination of the tunica vaginalis was performed weekly for four consecutive weeks. The intratunical route, in contrast to the parenteral route, achieves a high MXT level in the testicle and epididymis with a low serum level, resulting in low toxicity and high drug efficacy. This route may therefore be suitable for a more effective treatment of testicular and epididymal lesions, notably malignant tumors.