VPT 321: Veterinary Neuropharmacology (2+1) copy 1

α receptor antagonists

α - RECEPTOR ANTAGONIST

• Inhibit all responses mediated through α adrenergic receptors without affecting those mediated by β adrenergic receptors.
• Based on α-receptors subtypes these drug antagonize. These are further divided into
  • Non-selective α adrenergic receptor antagonists (block both alpha1 and alpha2 adrenoceptors)
    • Haloalkylamine derivatives Eg: Phenoxybenzamine, Dibenamine
    • Imidazoline derivatives: Eg: Tolazoline, Phentolamine
    • Ergot derivatives Eg: Ergotmine, Dihydroergotamine, Dihydroergotoxine
    • Miscellaneous drugs
      • Neuroleptics- Chlorpromazine, Haloperidol
      • Benzodioxan derivatives- Piperoxane, Dibozane
      • Dibenzepine derivatives- Azapetine
  • Selective α - adrenergic receptor antagonists
    • Selective α1 adrenergic receptor antagonists
      • Quinazoline derivatives- Prazosin, Terazosin, Doxazosin, Trimazosin
      • Indole derivatives- Indoramin
      • Miscellaneous drugs- Ketanserin, Urapidil
    • Selective α₂- adrenergic receptor antagonists- Yohimbine, Atipamazole