Cinnabloc Drug Interactions

Sedating antihistamines may enhance the sedative effects of CNS depressants including alcohol, barbiturates, hypnotics, opioid analgesic, anxiolytic sedatives, and antipsychotics. Sedative interactions apply to a lesser extent with the non-sedative antihistamines, they do not appear to potentiate the effects of alcohol but should be avoided in excess.
Sedating antihistamines have an additive antimuscarinic action with other antimuscarinic drugs such as atropine and some antidepressant. Potentially hazardous ventricular arrhythmias have occurred when the non-sedating antihistamines astemizole and terfenadine have been given concomitantly with drug liable to interfere with their hepatic metabolism, with other potentially arrhythmogenic drugs including those that prolong the QT interval, or with those likely to cause electrolyte imbalance. For full details see under Astemizole.
It has been suggested that some sedating antihistamines could mask the warning signs of damage caused by ototoxic drugs such as aminoglycoside antibiotics.
Antihistamines may suppress the cutaneous histamine response to allergen extracts and should be stopped several days before skin testing.