Thiamin status of patients treated with drug combinations containing 5-fluorouracil

Thiamin status has been assessed from whole blood transketolase measurements in patients with cancer in various sites being treated with drug combinations which included 5-fluorouracil (5-FU). Longitudinal measurements in nine patients showed that thiamin deficiency developed during treatment with 5-FU and was corrected by giving 100 mg thiamin per day. Similar evidence of thiamin deficiency was found in 26 patients who had been treated with 5-FU-containing regimens for varying periods of time but was not found in patients treated with regimens not containing 5-FU. Giving high doses of thiamin reduced the high levels of plasma and urinary ribonuclease which was of hepatic origin.