title: Antihistamines.
abstract: Antihistamines and their drug-drug interactions are reviewed in depth. The metabolism of "classic" or sedating antihistamines is coming to light through in vivo and in vitro studies. The polymorphic CYP 2D6 metabolic enzyme appears to be potently inhibited by many of these over-the-counter medications. The history of the discontinued "second-generation" antihistamines terfenadine and astemizole is reviewed to remind the reader why the understanding of the cytochrome P450 system became increasingly important when the cardiotoxicity of these drugs became apparent. The "third-generation" nonsedating antihistamines are also listed and compared. They have been exhaustively scrutinized for drug-drug interactions and cardiotoxicity, and they appear to have no serious drug-drug interactions at recommended doses.
authors.affiliation: Center for Geriatric Psychiatry, Tuality Forest Grove Hospital, Forest Grove, OR 97116, USA. scott.armstrong@tuality.org
authors.forename: Scott C
authors.initials: SC
authors.lastname: Armstrong
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Cozza
mesh_terms: D016589:Astemizole / Q000009:adverse effects / Q000627:therapeutic use; D065690:Cytochrome P-450 CYP2D6 Inhibitors; D004347:Drug Interactions; D006634:Histamine H1 Antagonists / Q000009:adverse effects* / Q000627:therapeutic use; D039563:Histamine H1 Antagonists, Non-Sedating / Q000009:adverse effects / Q000627:therapeutic use; D006801:Humans; D004366:Nonprescription Drugs / Q000009:adverse effects / Q000627:therapeutic use; D016593:Terfenadine / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D065690:Cytochrome P-450 CYP2D6 Inhibitors; D006634:Histamine H1 Antagonists; D039563:Histamine H1 Antagonists, Non-Sedating; D004366:Nonprescription Drugs; D016593:Terfenadine; D016589:Astemizole