The principal adverse effect of clonazepam is drowsiness, which occurs in about 50% of all patients on starting therapy. Sedation, muscle weakness, ataxia which generally decrease on continued administration and are consequence of CNS depression. Less frequent effects include vertigo, headache, confusion, depression, slurred speech or dysarthria, changes in libido, tremor, visual disturbances, urinary retention or incontinence, gastrointestinal disturbances, changes in salivation and amnesia. Some patients may experience a paradoxical excitation which may lead to hostility, aggression, and disinhibition, jaundice, blood disorders, and hypersensitivity reactions have been reported rarely. Respiratory depression and hypotension occasionally occur with high dosage and parenteral administration.