Chronic cough associated with interferon/ribavirin therapy for hepatitis C

The combination of pegylated interferon and ribavirin has become standard therapy for chronic hepatitis C infection. The occurrence of chronic cough associated with this treatment regimen has been reported, but the mechanism by which cough occurs has not previously been investigated. We measured cough reflex sensitivity, during and after completion of therapy, in four patients who developed chronic cough associated with interferon/ribavirin therapy.

Four patients without history of respiratory symptoms developed chronic cough temporally related to initiation of therapy with pegylated interferon and ribavirin for chronic hepatitis C infection. Cough resolved within 2-6 weeks after completion of a 48-week course of therapy. To measure cough reflex sensitivity, capsaicin cough challenge testing was performed 1 month prior to cessation of therapy, and 1 and 2 months after completion of treatment. In all patients, cough reflex sensitivity, as measured by C(5) , the concentration of capsaicin inducing 5 or more coughs, was significantly enhanced during treatment compared to 1 month after completion of therapy (P = 0·016).

Previous studies have observed that cough occurs more commonly in patients receiving the combination of interferon and ribavirin compared to interferon alone, thus implicating ribavirin as the causal agent. Our data demonstrate that it does so by reversible enhancement of cough reflex sensitivity. Clinicians should be aware of this potential treatment-related effect, so as to avoid unnecessary and costly diagnostic evaluations seeking an alternative aetiology of cough.