3. In infants and children, the side effects of first generation over-the-counter (OTC) antihistamines, such asdiphenhydramine (Benedryl) and hydroxyzine (Atarax) include:1. Reye’s syndrome.2. cholinergic effects.3. paradoxical CNS stimulation.4. nausea and diarrhea.
(3) Typically, first generation OTC antihistamines have a sedating effect because of passage into the CNS. However, insome individuals, especially infants and children, paradoxical CNS stimulation occurs and is manifested by excitement,euphoria, restlessness, and confusion. For this reason, use of first generation OTC antihistamines has declined, and secondgeneration product usage has increased. Reye’s syndrome is a systemic response to a virus. First generation OTCantihistamines do not exhibit a cholinergic effect. Nausea and diarrhea are uncommon when first generation OTC antihistaminesare taken.