ADRENERGIC AGONISTS & ANTAGONISTS 2 Flashcards
What is the effect of a -ADRENERGIC BLOCKERS
- Sympathetic control of the vasculature is mainly due to a1-adrenergic receptors
- Blockade of these receptors reduces the sympathetic tone of the blood vessels and decreases PVR.
PHENOXYBENZAMINE falls under what category and whats its effect?
NON-SELECTIVE a-ADRENERGIC BLOCKERS - blocks the release of ACh
- Irreversible antagonist of the a1 and a2 receptors..
- Unsuccessful for hypertension.
- Used in Pheochromocytoma
- Prior to surgical removal of the tumor.
- For chronic management of inoperable tumors.
PHENTOLAMINE falls under what category and whats its effect?
NON-SELECTIVE a-ADRENERGIC BLOCKERS
- Pheochromocytoma: control of hypertension during preoperative preparation and surgical excision.
- Diagnosis of pheochromocytoma: phentolamine blocking test.
- Prevention of dermal necrosis after extravasation of norepinephrine.
- Hypertensive crisis due to stimulant drug overdose.
What phenomenon is seen in EPINEPHRINE REVERSAL
All a-adrenergic blockers reverse the a-agonist effects of epinephrine.
- The vasoconstrictive a1 action of epinephrine is blocked, but vasodilation caused by activation of b2-receptors is not blocked.
- Therefore, the systemic blood pressure decreases in response to epinephrine given in the presence of phenoxybenzamine.
What are the a 1-SELECTIVE ADRENERGIC BLOCKERS and their common features?
PRAZOSIN TERAZOSIN DOXAZOSIN TAMSULOSIN
• DOC for BPH by Relax smooth muscle in the bladder neck,
prostate capsule and prostatic urethra improving urinary flow.
- Useful in the treatment of hypertension.
- Lower arterial blood pressure by relaxing both arterial and venous smooth muscle.
- First dose produces an exaggerated hypotensive response that can result in syncope (fainting).
- The first dose must be 1/3 or 1/4 of normal dose.
TAMSULOSIN falls under what category and whats its effect?
- a 1-BLOCKERS
- Tamsulosin is selective for α1A receptor which predominated in GU smooth muscle
- Approved for BPH.
- Little effect on blood pressure.
- Less likely to cause orthostatic hypotension
What are the NON-SELECTIVE B-BLOCKERS? What are they used for?
PROPRANOLOL (The prototype) NADOLOL TIMOLOL
- b-adrenergic antagonists slow heart rate and decrease myocardial contractility.
- Blocking b2 receptors in the lungs can precipitate a respiratory crisis in patients with COPD or asthma ( contraindicated)
- Metabolic effects: decrease Glycogenolysis and Glucagon secretion
ATENOLOL & METOPROLOL fall under what category and what are their effects?
• b1-SELECTIVE ADRENERGIC ANTAGONISTS
Useful in hypertensive patients with impaired pulmonary function.
• Useful in diabetic hypertensive patients who are receiving insulin or oral hypoglycemic agents.
ESMOLOL falls under what category and what its effect?
b 1-SELECTIVE ADRENERGIC ANTAGONISTS
- Ultra-short acting
- Half life ̴10 minutes
- Given IV
- For rapid control of ventricular rate in patients with atrial fibrillation or atrial flutter.
LABETALOL & CARVEDILOL fall under what category and what are their effects?
a 1- AND b-BLOCKERS:
LABETALOL • Competitive antagonist at b and a1 receptors.
- More potent as a b-antagonist than as an α- antagonist.
- Used in hypertension.
CARVEDILOL • Similar to labetalol.
- Has antioxidant properties.
- Used in hypertension and CHF.
PINDOLOL falls under what category and whats its effect?
PARTIAL b-AGONIST
• May be preferred in individuals with diminished cardiac reserve or a propensity to bradycardia.
What are the uses of b -BLOCKERS
- b-blockers lower blood pressure in hypertension by decreasing cardiac output.
- b-blockers, particularly timolol, are effective in diminishing intraocular pressure in glaucoma.
- b-blockers are effective for prophylaxis of migraine.
- b-blockers blunt sympathetic stimulation that occurs in hyperthyroidism.
- b-blockers decrease O2 requirement of heart muscle. = management of stable angina.
- b-blockers are indicated to control ventricular rate.
- b-blockers have a protective effect on the myocardium = MI
What are the ADVERSE EFFECTS of b-BLOCKERS?
Respiratory:
- Nonselective -blockers: Potentially lethal side effect in asthmatics.
- b1-selective drugs may be less likely to evoke bronchospasm.
Hypoglycemia
• Nonselective b-blockers may impair recovery from hypoglycemia in insulin-dependent diabetics. Due to blockade of b2 receptors in the liver.
Lipid metabolism
- Blockade of b receptors inhibits release of free fatty acids from adipose tissue.
- Both non-selective and β1-selective blockers increase TG and reduce HDL.
- Lipid levels are relatively unaffected by labetalol and partial agonists like pindolol.
a -METHYLTYROSINE (METYROSINE) falls under what category and whats its effect?
INHIBITORS OF NOREPINEPHRINE SYNTHESIS
- Competitive inhibitor of tyrosine hydroxylase.
- Used for management of malignant pheochromocytoma.
- Used in preoperative preparation of patients for resection of pheochromocytoma.
RESERPINE falls under what category and whats its effect?
INHIBITORS OF NOREPINEPHRINE STORAGE
- Irreversibly blocks VMAT. Vesicles cannot store norepinephrine and dopamine.
- This causes depletion of norepinephrine, since MAO degrades norepinephrine in the cytoplasm.
- Gradual decrease in blood pressure and slowing of cardiac rate.
- Used in the past to treat hypertension.
What are the tissues that are controlled by the ANS in the eye? What is their function and receptor?
