The most common side effects with Rebetol used in combination with interferon alfa-2b or peginterferon alfa-2b (seen in more than 1 patient in 10) are viral infections, pharyngitis (sore throat), anaemia (low red blood cell counts), neutropenia (low white blood cell counts), hypothryroidism (underactive thyroid gland), anorexia (loss of appetite), depression, insomnia (difficulty sleeping), emotional lability (mood swings), anxiety, dry mouth, headache, dizziness, impaired concentration, cough, dyspnoea (difficulty breathing), nausea, diarrhoea, abdominal (tummy) pain, vomiting, alopecia (hair loss), pruritus (itching), dry skin, rash, myalgia (muscle pain), arthralgia (joint pain), musculoskeletal pain (pain in the muscles and bones), reactions at the site of the injection including inflammation, fatigue (tiredness), fever, rigors (shaking chills), flu-like symptoms, asthenia (weakness), malaise (feeling unwell), irritability, weight loss and decreased growth rate.