Adverse reactions which have been reported with the use of antihistamines are as follows:
Central Nervous System
Sedation and sleepiness (often transient), dizziness, disturbed coordination,
confusion, restlessness, excitation, nervousness, tremor, irritability, insomnia, paresthesias, neuritis,
convulsions, euphoria, hallucinations, hysteria, faintness.
Allergic manifestation of rash and edema, excessive perspiration, urticaria,
Acute labyrinthitis, blurred vision, diplopia, vertigo, tinnitus.
Hypotension, palpitation, tachycardia, extrasystoles, anaphylactic shock.
Hemolytic anemia, leukopenia, agranulocytosis, thrombocytopenia.
Cholestasis, hepatic failure, hepatitis, hepatic function abnormality, dryness of
mouth, epigastric distress, anorexia, nausea, vomiting, diarrhea, constipation, jaundice.
Urinary frequency, difficult urination, urinary retention, early menses.
Dryness of nose and throat, thickening of bronchial secretions, tightness of chest and
wheezing, nasal stuffiness.
Fatigue, chills, headache, increased appetite/weight gain.
MAO inhibitors prolong and intensify the anticholinergic effects of
antihistamines. Antihistamines may have additive effects with alcohol and other CNS depressants, e.g.
hypnotics, sedatives, tranquilizers, antianxiety agents.