Comparison of two dosage regimens of the substrate for the [13C]methacetin breath test

The [13C]methacetin breath test ([13C]MBT) – a valuable non-invasive tool dedicated to the assessment of the liver metabolic capacity – still needs standardisation. The aim of this study was to check whether currently used dosage regimens of [13C]methacetin provide concordant [13C]MBT results in subjects with an atypical body constitution. Healthy volunteers: low body mass 95 kg (eight large body frame men) were recruited. They underwent [13C]MBT on separate days, taking in random order [13C]methacetin: a fixed 75 mg dose (FX75), or a 1 mg kg−1 body mass-adjusted dose (BMAD). Samples of expiratory air for 13CO2 measurement were collected over 3 h. The maximum momentary 13C elimination in breath air occurred earlier and was higher following BMAD than with FX75 in the low body mass females (T max 14.6±1.0 min vs. 22.1±2.4 min, p=0.019; D max 41.9±2.9 % dose h−1 vs. 36.6±3.6 % dose h−1, p=0.071). In the high body mass men, T max remained unchanged, whereas D max was sl...