Like all medicines, this medicine can cause side effects, although not everybody gets them.
Nervous system side effects such as dizziness may be higher after a single 'loading' dose.
Patients must be advised to talk to the doctor or pharmacist if they get any of the following: Very common (may affect more than 1 in 10 people): Headache; Feeling dizzy or sick (nausea); Double vision (diplopia).
Common (may affect up to 1 in 10 people): Short jerks of a muscle or group of muscles (myoclonic seizures); Problems in keeping balance, difficulties in coordinating movements or walking, shaking (tremor), tingling (paresthesia) or muscle spasms, falling easily and getting bruises; Troubles with memory, thinking or finding words, confusion; Rapid and uncontrollable movements of the eyes (nystagmus), blurred vision; A spinning sensation (vertigo), feeling drunk; Being sick (vomiting), dry mouth, constipation, indigestion, excessive gas in the stomach or bowel, diarrhoea; Decreased feeling or sensitivity, difficulty in articulating words, disturbance in attention; Noise in the ear such as buzzing, ringing or whistling; Irritability, trouble sleeping, depression; Sleepiness, tiredness or weakness (asthenia); Itching, rash.
Uncommon (may affect up to 1 in 100 people): Slow heart rate, palpitations, irregular pulse or other changes in the electrical activity of the heart (conduction disorder); Exaggerated feeling of wellbeing, seeing and/or hearing things which are not there; Allergic reaction to medicine intake, hives; Blood tests may show abnormal liver function, liver injury; Thoughts of harming or killing oneself or attempting suicide: advise the patient to inform the doctor straightaway; Feeling angry or agitated; Abnormal thinking or losing touch with reality; Serious allergic reaction which causes swelling of the face, throat, hands, feet, ankles, or lower legs; Fainting; Abnormal involuntary movements (dyskinesia).
Not known (frequency cannot be estimated from available data): Abnormal rapid heartbeat (ventricular tachyarrhythmia); A sore throat, high temperature and getting more infections than usual. Blood tests may show a severe decrease in a specific class of white blood cells (agranulocytosis); A serious skin reaction which may include a high temperature and other flu-like symptoms, a rash on the face, extended rash, swollen glands (enlarged lymph nodes) [Blood tests may show increased levels of liver enzymes and a type of white blood cell (eosinophilia)]; A widespread rash with blisters and peeling skin, particularly around the mouth, nose, eyes and genitals (Stevens-Johnson syndrome), and a more severe form causing skin peeling in more than 30% of the body surface (toxic epidermal necrolysis); Convulsion.
Additional side effects in children: The additional side effects in children were fever (pyrexia), runny nose (nasopharyngitis), sore throat (pharyngitis), eating less than usual (decreased appetite), changes in behaviour, not acting like themselves (abnormal behavior) and lacking in energy (lethargy). Feeling sleepy (somnolence) is a very common side effect in children and may affect more than 1 in 10 children.
Reporting of side effects: If the patient gets any side effects, they must be advised to talk to the doctor or pharmacist. This includes any possible side effects not listed in this monograph. Side effects can also be reported directly via the local reporting system. Reporting side effects can help provide more information on the safety of this medicine.
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