This study sought to decribe, quantify, and classify any adverse reactions occurring in patients with chronic hepatitis C treated with peginterferon and ribavirin, as well as verify the occurrence of potential medication interactions. The most prevalent reactions were fatigue (84.8%), fever (83%), weight loss (80%), irritability (74%), and body pain (72%). Most of the reactions were classified as mild (95%), whereas 4.5% were classified as moderate and 0.4% as severe. Adverse reactions led to the rearrangement of therapy for 9 patients (20%), where there was a reduction in dose for 7 (15%), temporary interruption of treatment for 5 (11%), and permanent discontinuation for 3 patients (7%). A total of 11 potential medication interactions were identified in 9 patients (20%), with the most frequent between peginterferon-α2a and captopril (45%). Given the above, it is observed that the treatment of chronic hepatitis C is marked by several adverse reactions of varying severity, which can interfere with the patient's quality of life or in treatment compliance, and that can be aggravated by potential drug-drug interactions.