Nuclear medicine liver function tests for pregnant women and children. 1. Breath tests with 14C-methacetin and 13C-methacetin.

Stable isotopes, such as 13C, should be substituted for the long-lived radionuclide 14C in the 14C breath test when doing liver function tests in children and pregnant women. For comparison 13C, 15N-methacetin and 14C-methacetin were synthesized as suitable diagnostic agents. Methods are described for the measurement of 14C and 13C in the breath. After oral administration of labelled methacetin to healthy subjects and patients with liver diseases a good correspondence between 13C- and 14C-measurements in the same subject on the one hand, and a good discrimination between controls and patients on the other hand were shown. Findings with regard to 14C measurements in urine are discussed supporting the supposed advantage of 13C-methacetin over 14C-methacetin application.