Adrenergic Drugs

Adrenergic Drugs

1. Sympathomimetics/adrenergic agonists/adrenergic drugs

   • Fight or flight response.
   • Shock and hypotension
   • Much of the same action as anticholinergics, except these drugs are more specific and have a wider therapeutic application.
   • Catecholamines: Same structure as NE, shorter duration of action
     • Must be given parenterally
   • Noncatecholamines: Not rapidly destroyed by MAO or COMT, so longer duration of action
     • Can be given orally
   • Most act directly by binding to and activating adrenergic receptors, but some act indirectly by causing release of NE or by inhibiting reuptake or destruction of NE
   • Effects are predictable based on which receptor subtype is stimulated. Here's what they treat:
     • Alpha 1: Nasal congestion, hypotension, mydriasis for ophthalmic exams
       • Alpha 2: Hypertension
         • Beta 1: Cardiac arrest, heart failure, and shock
           • Beta 2 receptor: Asthma and premature contractions
             • Beta 3: Overactive bladder
   • Side effects such as tachycardia, hypertension, dysrhythmias may limit therapy
     • CNS excitement and seizures can occur at a large dose
       • Dry mouth, nausea, vomiting, and anorexia can also occur

2. Adrenergic blocking drugs/adrenergic antagonists/sympatholytics

   • Alpha-adrenergic agonists: Used for effects on vascular smooth muscle
     • Relaxes vascular smooth muscle in small arteries, causing vasodialtion and decreasing blood pressure
     • Can cause orthostatic hypotension, reflex tachycardia, nasal congestion, and impotence
     • Phentolamine is used to diagnose pheochromocytoma (pg.151)
   • Greater therapeutic application.
   • Similar effect to parasympathomimetics
   • Treatment of hypertension
   • Beta-adrenergic agonists: Decrease rate and force of heart contraction and slow electrical conduction through AV node
     • Used primarily for hypertension, but can also work for migraines, angina pectoris, dysrhythmias, heart failure, MI, and narrow angle glaucoma
     • May exacerbate heart failure in some patients.
       • Increases risk of hypotension and bradycardia. Can cause bronchial constriction, hypoglycemia, diarrhea, nausea, vomiting, muscle cramps, rash, blurred vision, fatigue, depression, and erectile dysfunction
     • Abrupt discontinuation can cause acute resurgence of symptoms.