Uncommon side effects (affects 1 to 10 users in 1,000) • allergic reaction • loss of appetite, decreased appetite • falling asleep suddenly without warning, psychotic disorders including abnormal thinking about reality and behaviour (paranoid psychosis), unusual urge to perform an action that is harmful including excessive gambling and repetitive meaningless actions, increased sex drive, anxiety, sleep problems, nightmares, disorientation • fainting, fainting due to a fall in blood pressure, slow movement or extended spasm in group of muscles, increased sleepiness, feeling of tiredness or lack of energy (lethargy), reduced concentration, loss of memory, numbness or tingling sensation, food and drink tasting different, poor balance, tremors • visual disturbances such as seeing colours or lights, or blurred vision • a feeling of dizziness or "spinning" (vertigo) • abnormal heart rhythm, increased heart rate, feeling of heart beat (palpitation) • high blood pressure, low blood pressure • cough, hiccups, shortness of breath • stomach discomfort and pain • generalised itching, skin rash, skin irritation • swelling of the joints • being unable to achieve or maintain an erection • being unable to walk properly, feeling abnormal, weight increase