[C-13]AMINOPYRINE BREATH TEST DETECTS ALTERED LIVER-METABOLISM CAUSEDBY LOW-DOSE ORAL-CONTRACEPTIVES

The [C-13]aminopyrine breath test measures hepatic mixed function oxid ase activity. The cumulative percent dose recovered over 2 hr is a sen sitive indicator of hepatic dysfunction; values less than or equal to 7.0% have been shown to indicate severe liver disease. Previous studie s have suggested that the test results may be influenced by the use of oral contraceptive steroids, We compared the results from five non-or al contraceptive-using women with those from 31 women whose duration o f oral contraceptive steroid usage ranged from 4 to 204 months, The wo men were taking one of four oral contraceptive formulations that diffe red in the amounts of estrogen (20, 35, or 50 mu g with 1 mg progester one) and progesterone (35 mu g estrogen with stepped levels of progest erone of 0.5, 0.75, and 1.0 mg). The [C-13]aminopyrine breath test was performed on days 21 and 28 of the menstrual cycle, Cumulative percen t dose recovery values among the normal menstrual cycle of non-oral co ntraceptive steroid-using women were 12.1 +/- 1.6 and 11.8 +/- 1.5% (m ean +/- SD). In contrast, oral contraceptive steroid users showed a ma rked reduction in cumulative percent dose recovery at 21 days, averagi ng 6.1 +/- 2.3% (P < 0.001), and returned to normal values (10.2 +/- 3 .6%) at 28 days in most women (seven days after oral contraceptive ste roid usage was paused). The adverse impact on hepatic mixed function o xidase by oral contraceptive formulations did not differ on the basis of estrogen or progesterone content. The adverse impact of oral contra ceptive usage on the mixed function oxidase activity measured by the [ C-13]aminopyrine breath test must be considered for women of childbear ing potential.