Adrenergic Blockers

Question 1

Classification

Alpha blockers

Answer 1

1. Non selective :
   a. Reversible- phentolamine
   b. Irreversible- phenoxybenzamine
2. Selective a1- prazosin, terazosin, tamsulosin
3. Selective a2 - yohimbine

Question 2

Phenoxybenzamine Pharmacological effects

Answer 2

1. Peripheral venodilation

2. Cardiac stimulation

Question 3

Therapeutic uses of alpha blockers

Answer 3

1. Pheochromocytoma: phenoxybenzamine is used up control hypertension and restore blood volume. Also used in inoperable cases.

Administration of beta blockers with prior administration of alpha blockers.

2. Hypertensive emergencies : i.v phentolamine
   From pheocromocytoma, clonifibe withdrawal, cheese reaction.
3. Essential hypertension:
4. Benign prostatic hyperplasia: selective a1 blockers used to reduce urinary flow after resection.
5. Tissue necrosis : phentolamine
6. Male sexual dysfunction: phentolamine with papaverine
7. CCF , PVD

Question 4

Classification

Beta blockers

Answer 4

1. First gen : non selective : propranolol, sotalol
2. Second gen :b1 selective : metoprolol, atenolol
3. Third gen : with additional vasodilatory effect :
   Non selective: labetalol
   Selective: betaxolol

Question 5

Pharmacological properties

Answer 5

1. Heart : negative chronotropic,inotrophic, dromotrophic.
   Decreased CO,HR, SA and AV node activity, automaticity, o2 requirement.

Blood vessels: initial increases in pvr, later fall in systolic and diastolic BP.

Renin release from JG apparatus.

2. Respiratory system : severe brochospasm.
3. Skeletal muscles- on chronic use, weakness and tiredness.
4. Metabolic effects: inhibits glycogenolysis, mask warning signs of hypoglycaemia. Chronic use decreases HDL: LDL ratio.
5. Eye : decreases IOP.

Question 6

Pharmacokinetics

Answer 6

1. Highly lipid soluble
2. Extensive first pass metabolism: low bioavailability
3. Crosses bbb
4. Large volume of distribution
5. Excreted in urine

Question 7

Adverse effects

Answer 7

1. CVS : may precipitate CCF, may worsen pvd, can exacerbate variant angina.
2. Respiratory: severe brochospasm
3. Cns: hallucinations, fatigue, mental depression
4. Mask warning signs of hypoglycaemia
5. Muscle weakness and tiredness
6. Withdrawal symptoms : up regulation in prolonged blockade

Question 8

Drug interactions

Answer 8

1. Propranolo + verapamil : CCF, bradyarrthymias, heart block, cardiac arrest
2. Propranolo + lignocaine: reduced clearance
3. Beta blockers + cholestyramine: interfere with beta blockers absorption
4. Beta blockers + insulin: inhibits glycogenolysis
5. Propranolol + NSAIDs: decreases antihypertensive effect of beta blockers
6. Propranolol + chlorpromazine : interferes with first pass metabolism of chlorpromazine and increases its bioavailability.

Question 9

Therapeutic uses of beta blockers

Answer 9

1. Hypertension
2. Angina prophylaxis and MI
3. Cardiac arrthymias
4. CCF
5. Pheochromocytoma
6. Glaucoma
7. Migraine prophylaxis
8. Hyperthyroidism
9. Essential tremors
10. Alcohol withdrawal
11. Dissecting aortic aneurysms
12. Acute anxiety state