Clinical use of thymidine as a rescue agent from methotrexate toxicity.

Thymidine has been available for clinical research as a rescue agent since 1978 under sponsorship of the Division of Cancer Treatment, National Cancer Institute. Renal insufficiency following administration of high dose methotrexate results in prolonged exposure to toxic concentrations of drug. Thymidine has been used in conjunction with leucovorin and alkaline hydration to protect patients with acute renal dysfunction from life-threatening methotrexate toxicity. The outcome of eight cases in which thymidine was released under the special exception mechanism to treat patients who developed acute renal failure following methotrexate are reported. The clinical trials using thymidine in combination with methotrexate in patients with normal renal function are also reviewed.