Assessment of Aminopyrine Metabolism in Man by Breath Analysis after Oral Administration of¹⁴C-Aminopyrine

To determine whether hepatic drug metabolism might be conveniently assessed by a breath analysis technic, 4-dimethyl-14C-amino-antipyrine (aminopyrine) was administered orally to healthy ambulant and nonambulant volunteers and to patients with portal cirrhosis; some of the volunteers were restudied after pretreatment with either phenobarbital or disulfiram. 14CO2 output was estimated semiquantitatively from interval breath samples. Aminopyrine metabolic clearance rate and 12-hour breath 14CO2 output in the healthy volunteers studied before and after drug pretreatment correlated highly(r = 0.91). The metabolic clearance rate was 46 ± 7 ml per minute (mean ± S.E.) in the patients with portal cirrhosis, and 122 ± 20 ml per minute in the healthy controls (p < 0.01). Twelve-hour breath 14CO2 output was 13.8 ± 1.5 per cent in the patients with portal cirrhosis, and 32.6 ± 2.3 per cent in the nonambulant controls (p < 0.01). The data suggest that in vivo breath analysis after administration of 14C-aminopyrine provides useful information about hepatic drug metabolism in health and disease. (N Engl J Med 291:1384–1388, 1974)