PCOL

• Alpha receptor Antagonist


  • Nonselective alpha antagonist
  • A1 selective antagonist
  • A2 selective antagonist
• Beta receptor Antagonist


  • Nonselective B antagonist
  • B1-selective antagonist
  • B2 selective Antangonist
• Adrenergic Drugs


  Blocks the effect of the receptor. Thus, antagonist!
• Drug's effect may vary based on selectivity for alpha and beta receptors
• Non Selective alpha blocker

  • Phenoxybenzamine
  • Causes irreversible blockade to the alpha receptor (14-48 hrs), noncompetitive antagonist
  • Somehow A1 selective
  • Inhibits the receptors in the presynaptic adrenergic nerve terminals
  • Blocks 5HT, Histamine, Ach, aside from alpha receptors
• Phentolamine


  • Nonselective, reversible, and competitive alpha inhibitor
  • By blocking alpha 1 receptor = vasodilation = decreased peripheral vascular resistance
  • By blocking alpha 2 receptor = increased release of NE, which binds with B1 = cardiac stimulation
• Alpha 1 - selective antagonist

  • Prazosin
  • Competitive antagonist used in HTN
  • Relaxes arterial and venous vascular smooth muscle
  • Also used in men with urinary retention symptoms due to benign prostatic hyperplasia, BPH (enlarged prostate causes obstruction)
  • Causes relaxation of the prostate = urine
• Terazosin


  Reversible alpha 1 selective antagonist with similar indication as prazosin
• Doxazosin


  • Similar indication with prazosin
  • Differs from prazosin and terazosin by having a longer half life (22 hrs, compared to 3 hours for prazosin and 9-12 hrs for terazosin)
• Tamsulosin


  • Competitive alpha 1 antagonist
  • Used for: urinary retention symptoms in patients with BPH
  • Greater potency in inhibiting contraction in the prostate smooth muscle than the vascular smooth muscle, thus, no anti-HTN effect
• Alfuzosin


  Similar indication with tamsulosin
• Alpha 2 selective antagonist


  • Yohimbine
  • Sometimes used as a treatment in the treatment of orthostatic hypotension because it promotes the release of NE = vasoconstriction
  • But it was mainly used to treat male erectile dysfunction BUT it has been replaced by phosphodiesterase-5-inhibitors
  • It can elevate the blood pressure
  • It reverses the antiHTN effect of clonidine
• Nonselective Beta blockers


  • Propranolol
  • THE PROTOTYPICAL B-BLOCKING DRUG
  • Major use: Tx for HTN by decreasing the production of renin = decreased BP
  • Warning: Since it is nonselective, it should be used with caution for patients with COPD and Asthma as this might cause bronchoconstriction
  • Low doses of propranolol have been found beneficial for performance anxiety or stage fright
• Nadolol


  • Similar indication to propranolol
  • Very long duration of action
• Sotalol


  Often used in arrhythmias rather than HTN
• Timolol


  • Similar indication to HTN
  • Additionally, this drug is different as this has excellent ocular hypotensive effects when administered topically in the eye = used in glaucoma
• B1-selective blockers


  • Nebivolol
  • It is the MOST HIGHLY selective B1-adrenergic receptor blocker. Additionally, it has vasodilating effect
  • Also used in HTN
• Betaxolol


  • Also used in HTN
  • It can also decrease intraocular pressure, thus, can be used as a treatment for glaucoma
• Atenolol


  • They are used in HTN
  • And as a B1 selective antagonist, it does not block B2 receptors, thus, no bronchoconstriction. Which means that it is relatively safer for patients with asthma
• Metoprolol


  Similar indication to Atenolol
• Esmolol


  • It is an ultra-short-acting B1 selective (THUS, ESMOL = 10 mins half life)
  • Useful in controlling supraventricular arrhythmias, arrhythmias associated with thyrotoxicosis, perioperative HTN, and MI
• Beta blocker with Alpha 1 blocking effect

  • Labetalol
  • Carvedilol
• B antagonists are used in HTN, arrhythmias, heart failure
• • Warning for B1 -blockers users:
  • 1. It may cause bradycardia
  • 2. It may exacerbate preexisting asthma
  • 3. Hypoglycemic episodes may be exacerbated
• Tocolytics


  • Ritodrine
  • Isoxsuprine
  • Terbutaline