Ziltem/Ziltem IM Adverse Reactions

The most common adverse effect of the sedating antihistamine is CNS depression, with effects varying from slight drowsiness to deep sleep, and including lassitude, dizziness, and incoordination (although paradoxical stimulation may occasionally occur, especially at high doses and in children or the elderly). These sedative effects, when they occur, may diminish after a few days of treatment.
Other adverse effects that are more common with the sedating antihistamines include headache, psychomotor impairment and antimuscarinic effects, such as dry mouth, thickened respiratory-tract secretions, blurred vision, urinary difficulty or retention, constipation and increased gastric reflux.
Antihistamines sometimes cause rashes and hypersensitivity reactions (including bronchospasm, angioedema and anaphylaxis) and cross-sensitivity to related drugs may occur. Photosensitivity can be a problem, particularly with the phenothiazine antihistamines. Blood disorders, including agranulocytosis, leucopenia, haemolytic anaemia and thrombocytopenia, although rare, have been reported. Jaundice has also been observed, particularly with the phenothiazine antihistamines.
Other adverse effects that have been reported with the antihistamines include convulsions, sweating, myalgia, paraesthesias, extrapyramidal effects, tremor, sleep disturbances, depression, confusion, tinnitus, hypotension and hair loss.
Despite reports suggesting a possibility of human fetal abnormalities resulting from the use of some antihistamines, especially the piperazine derivatives, a causal relationship has largely been rejected.