Food‐effect study on uracil and dihydrouracil plasma levels as marker for dihydropyrimidine dehydrogenase activity in human volunteers

Aims This study aimed to determine the effect of food intake on uracil and dihydrouracil plasma levels. These levels are a promising marker for dihydropyrimidine dehydrogenase activity and for individualizing fluoropyrimidine anticancer therapy. Methods A randomized, cross‐over study in 16 healthy volunteers was performed, in which subjects were examined in fasted and fed state on two separate days. In fed condition, a high‐fat, high‐caloric breakfast was consumed between 8:00 h and 8:30 h. Whole blood for determination of uracil, dihydrouracil and uridine plasma levels was drawn on both test days at predefined time points between 8:00 h and 13:00 h. Results Uracil levels were statistically significantly different between fasting and fed state. At 13:00 h, the mean uracil level in fasting state was 12.6 ± 3.7 ng ml−1 and after a test meal 9.4 ± 2.6 ng ml−1 (P