Aminophenazone (or aminopyrine) is a pyrazolone with analgesic, anti-inflammatory, and antipyretic properties but has risk of agranulocytosis. A breath test with 13C-labeled aminopyrine has been used as a non-invasive measure of cytochrome P-450 metabolic activity in liver function tests. It is also used in measuring the total body water in the human body system.
^ abCaubet, M. S.; Laplante, A.; Caillé, J.; Brazier, J. L. (4 Jan 2007). "[13C]Aminopyrine and [13C]Caffeine Breath Test: Influence of Gender, Cigarette Smoking and Oral Contraceptives Intake". Isotopes in Environmental and Health Studies. 38 (2): 71–77. doi:10.1080/10256010208033314.