Table 2.

Side effects of the different generations of antihistamines

Class	Central nervous system	Cardiovascular	Toxic high dose
First-generation	agitation, confusion, dystonia, dyskinesia, hallucinations, headache impairment in coordination, learning, memory, psychomotor and sensorimotor functions, and sedation	dose-dependent sinus tachycardia, reflex tachycardia, atrial refractory period prolongation and supraventricular arrhythmias	severe CNS and cardiac side effects, may lead to death unless treated
Second-generation	variable (such as sedation with cetirizine) Minimal or no side effects	no side effects	no severe side effects or deaths reported

CNS, central nervous system