Antihistamines

• 1^st Generation H1 receptor antagonists
• May antagonize muscarinic receptors leading to anticholinergic effects
  • Decrease PNS = SNS effects
  • Urinary retention, retention due to impaired detrusor contraction
• Azelastine (Astelin)
• 2^nd Generation H1 receptor antagonists
• Fexofenadine (Allegra)
• Loratadine (Claritin)
• Desloratadine (Clarinex)
• Cetirizine (Zyrtec)
  • SE: sedation, arrhythmias in overdose
• H2 receptor antagonists
• Cimetidine (Tagamet)
• Famotidine (Pepcid)
• Ranitidine (Zantac)