In therapeutic doses, the drug is usually well tolerated. Allergic reactions are possible (skin rash, itching, hives, Quincke's edema, rarely anaphylactic shock, in very rare cases, malignant exudative erythema (Stevens-Johnson syndrome), toxic epidermal necrolysis (Lyell's syndrome).
Rarely (usually chronic administration, or high doses) - agranulocytosis, leukopenia, thrombocytopenia; disturbance of kidney function: oliguria. anuria, proteinuria, interstitial nephritis; bronchospasm, lowering of blood pressure, gastralgia, staining of urine in red.
Very rarely - anticholinergic effects (dry mouth, decreased sweating, paresis of accommodation, tachycardia, urine retention.).
All side effects should be reported to your doctor.