Allergic reactions: urticaria, itching, Quincke's edema, exanthema, bullous rash.
From the nervous system: sweating, dizziness, headache, weakness, increased fatigue, retardation,paradoxical stimulation of the central nervous system (nervousness, agitation, anxiety, tremor, muscle spasms, euphoria, emotional lability, hallucinations), drowsiness, sleep disturbance, confusion, impaired coordination of motion, convulsions of the central genesis (with concomitant administration of antipsychotics), depression, amnesia, violation of cognitive function, paresthesia, unsteadiness of gait.
From the digestive system: dry mouth, nausea, vomiting, flatulence, abdominal pain, constipation, diarrhea, difficulty in swallowing; an increase in the activity of "hepatic" enzymes, usually without the development of jaundice.
From the cardiovascular system: tachycardia, orthostatic hypotension, syncope, collapse.
From the endocrine system: hypoglycemia, up to hypoglycemic coma.
From the urinary system: difficulty urinating, dysuria, urinary retention. With prolonged admission in doses significantly exceeding the recommended - nephrotoxicity (interstitial nephritis, papillary necrosis).
From the sense organs: impaired vision, taste.
From the respiratory system: dyspnoea.
From the skin: multiforme exudative erythema (including Stevens-Johnson syndrome), toxic epidermal necrolysis (Lyell's syndrome).
On the part of the organs of hematopoiesis: sulfgemoglobinemia. With prolonged admission in doses much higher than recommended - aplastic anemia, pancytopenia, agranulocytosis.
Other: violation of the menstrual cycle.
With prolonged use - the development of drug dependence. With a sharp cancellation, the "cancellation" syndrome.