1.        SELECTIVE ALPHA-1 ANTAGONISTS

[Mechanism of action]

  • Block alpha-1 receptors located in the body, especially on the arterioles
  • antagonists will cause a decrease in blood pressure and in peripheral resistance

Drugs: PRAZOSIN, DOXAZOSIN, TERAZOSIN AND TAMSULOSIN

[Treatment]

  • Very good for hypertension due its vasodilation effect
  • Helps manage pheochromocytoma (tumor of adrenal medulla that releases high amount of epinephrine) by reducing blood pressure
  •  Helps manage benign prostatic hyperplasia (BPH- give selective a1 blockade b/c it relaxes bladder sphincter)
  • Drugs of choice for hypertension given in combinations: alpha-1 antagonist, beta blocker and diuretic

[Side effects]

  • May cause reflex tachycardia; THEREFORE, give in combination with a BETA blocker to stop the tachycardia
  • The drop in BP will stimulate the renin-angiotensin system to cause salt and water retention; to prevent this, give a DIURETIC

 

2.       NONSELECTIVE ALPHA BLOCKERS

[Mechanism of action]

  • These drugs block both alpha-1 and alpha-2 receptors

Drugs: PHENTOLAMINE & PHENOXYBENZAMINE

  • Phentolamine: competitive inhibitor; acute effect
  • Phenoxybenzamine: noncompetitive inhibitor; used in hypertensive crisis; given IV

 3.       SELECTIVE ALPHA-2 BLOCKERS

  • Yohimbine: treats sexual impotence, and orthostatic hypotension
  • Mirtazapine: used to treat depression
  • MOA: They increase norepinephrine causing an increased BP

 

 

BETA BLOCKERS

Note: the rule is that any beta (olol’s) drug that starts with the letters A-M is BETA-1 selective blocker-except Albuterol which is a beta agonist. Starting with letters P-Z is BETA-2 selective blocker

1.       BETA-1 BLOCKERS

[Mechanism of action]

  • Decreases renin and aqueous secretion)
  • Treat: hypertension, asthmatics
  • Side effects: causes bradycardia
  • Contraindications: Don’t give beta2 blockers to diabetics because it decreases insulin secretion

 

2.       BETA-2 BLOCKERS

  • Pindolol & propranolol (very sedative; treat tremors and migraine)
  • give TIMOLOL to treat glaucoma
  • Acebutolol and pindolol are partial agonists (therefore you won’t get maximum blockade)
  • Atenololis better to give to depressed patients because it is water soluble; doesn’t depress CNS

 

 

[Side effects of b blockers]:

  • Hyperlipidemia (acebutolol and pindolol don’t increase lipids)
  • Hypoglycemia due to decreased insulin release
  • May cause vasospasm or bronchospasm
  • Contraindications: DO NOT GIVE TO ASTHATICS , DIABETICS and vasospastic disorders