Sympathomimetic drugs (Part II)

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Sympathomimetic drugs (Part II)

Sympathomimetic drugs Part II

Selectivity for alpha versus β receptors (SAR):


  • N-alkyl substitution… increases potency at β and decreases potency at alpha receptors.
  • Phenol group…important for β more than alpha agonists.
  • alpha-substitution…increases alpha2 selectivity.
  • N-alkyl extension… good for β selectivity.

Examples of alpha and beta agonists

  • Selective alpha1-agonists.
  • Act as vasoconstrictors.
  • Used topically for nasal congestion.


  • Selective alpha2 agonist (centrally) leads to inhibition of sympathetic outflow from the CNS.
  • Used in hypertension
  • Central nervous (CNS) system stimulant 
  • Increasing levels of dopamine and noradrenaline in the synaptic cleft.
  • Long-acting beta-2 agonist
  • For Asthma and COPD
  • Adrenergic agonist 
  • Neurotransmitter
  • Adrenergic agonist 
  • Neurotransmitter
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