Cardiovascular: Hypotension, headache, palpitations, tachycardia, extrasystoles.
Hematologic: Hemolytic anemia, thrombocytopenia, agranulocytosis.
Nervous system: Sedation, sleepiness, dizziness, disturbed coordination, fatigue, confusion, restlessness, excitation, nervousness, tremor, irritability, insomnia, euphoria, paresthesia, blurred vision, diplopia, vertigo, tinnitus, acute labyrinthitis, neuritis, convulsions.
Gastrointestinal: Epigastric distress, anorexia, nausea, vomiting, diarrhea, constipation.
Genitourinary: Urinary frequency, difficult urination, urinary retention, early menses.
Respiratory: Thickening of bronchial secretions, tightness of chest and wheezing, nasal stuffiness.
Interference with laboratory tests: Diphenhydramine will interfere with wheal formation in skin testing for skin sensitizing reaginic antibodies. However, the drug does not interfere with serological tests for IgE such as radioallergosorbent test.
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