QT Prolongation with Variable Association with Torsade (see Torsade, [[Torsade]])
Agents
Diphenhydramine (Benadryl) (see Diphenhydramine, [[Diphenhydramine]]): QT prolongation with definite association with torsade
Hydroxyzine (Atarax, Vistaril) (see Hydroxyzine, [[Hydroxyzine]]): QT prolongation without definite association with torsade
Physiology: class effect
Gastrointestinal Adverse Effects
Constipation
Diarrhea
Dry Mouth
Nausea and Vomiting
Neurologic Adverse Effects
Blurred Vision
Dizziness
Headache
Hallucination/Psychosis
Insomnia
Tinnitus
Sedation: more common with first-generation antihistamines (due to relative lack of selectivity for the H1-receptor and ability to cross the blood-brain barrier)
Other Adverse Effects
Urinary Retention
Adverse Effects (Second-Generation Agents)
Cardiovascular Adverse Effects
QT Prolongation with Variable Association with Torsade (see Torsade, [[Torsade]])
Agents
Astemizole (Hismanal) (see Astemizole, [[Astemizole]]): QT prolongation with definite association with torsade
Ebastine: QT prolongation without definite association with torsade
Loratidine (Claritin) (see Loratidine, [[Loratidine]]): QT prolongation with definite association with torsade
Mizolastine: QT prolongation without definite association with torsade
Terfenadine (Seldane) (see Terfenadine, [[Terfenadine]]): QT prolongation with definite association with torsade