As RBV is a guanine analogue it is not specific for HCV and some severe adverse effects are known. The most important adverse effect is haemolytic anaemia,which usually occurs during the first weeks of treatment (>10% of the treated patients, depending on co-medication). Other adverse reactions that were frequently reported were: neutropenia, anorexia, depression/insomnia, headache, dizziness, dyspnea, and cough 5.