Sympathetic Drugs

Alpha Agonists

Alpha agonists are described under vasopressors and inotropes.

Adrenoreceptor Antagonists

Centrally acting act on the BP control centre in the brain. It is thought that they act on α2 receptors to inhibit NE release

• side effects include sedation

• methyldopa
• clonidine

Beta-blockers

• decrease cardiac output (both HR and contractility)
• also decrease renin release, leading to lowered Na, water retention and vasodilation
• makes exercise difficult

 

Drugs

• propanolol: β1 and β2 antagonist
• metoprolol: β1 antagonist
• atenolol
• acebutamol
• bisoprolol

 

Uses

 

Mechanism(s)

• competitively inhibits beta1 receptors reducing HR, contractility, BP, and MVO2
• increases duration of diastole
• increased preload
• profound fatigue
• loss of glycemic control
• impotence
• contraindicated in asthma

• decreases heart rate
• decreases contractility
• decreases afterload

 

Adverse Effects

increasing doses of beta blockers causes loss of cardioselectivity.

short term

• avoid acute adminstration in unstable patients with hypotension or overt HF
• bradycardia and heart block
• bronchospasm
• peripheral vasoconstricion
• fatigue, lethargy

long term

• depression, vivid dreams, nightmares

Contraindications

• absolute: asthma
• relative:
  • tendency to bronchospasm
  • insulin dependent T2DM
  • conduction system disease
  • peripheral vascular disease

Alpha-blockers

• block α1 receptors on vascular smooth muscle cells, increasing vasodilation

• parazosin

Acetylcholine Agonists

 

Drugs

 

Uses

 

Mechanism(s)

 

Adverse Effects

Acetylcholine Antagonists

 

Drugs

 

Uses

 

Mechanism(s)

 

Adverse Effects