Cetirizine (Ceti-Med) may enhance the sedative effects of CNS depressants including alcohol, barbiturates, hypnotics, opioid analgesics, anxiolytic sedatives and neuroleptic. MAOIs may enhance the antimuscarinic effects of antihistamines, and antihistamines have an additive antimuscarinic action with antimuscarinic drug such as atropine and tricyclic antidepressant.