Short report: interferon‐α decreases 14C–aminopyrine breath test values in patients with chronic hepatitis C

SUMMARY Objective: To investigate the effect of interferon-α on cytochrome P-4 50 dependent microsomal function. Methods: The 14C-aminopyrine breath test was performed before, during and after a standard dose of interferon-α (3 000000 units three times per week) was administered for at least six months (nine patients with chronic hepatitis C). Results : Mean aminopyrine breath test values obtained during therapy were significantly lower than either pre- or post-treatment, the degree of reduction varying widely between individuals. Pre- and post-treatment aminopyrine breath test values did not differ significantly. Conclusion: Interferon therapy is associated with a significant and transient inhibition of cytochrome P-450 activity, which should be taken into account when prescribing concurrent therapy with drugs metabolized by this pathway.