Short report: interferon-alpha decreases 14C-aminopyrine breath test values in patients with chronic hepatitis C

OBJECTIVE: To investigate the effect of interferon-alpha on cytochrome P-450 dependent microsomal function. METHODS: The 14C-aminopyrine breath test was performed before, during and after a standard dose of interferon-alpha (3,000,000 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.