BETA BLOCKERS

Question 1

BETA BLOCKERS are used for the treatment of

Answer 1

1-hypertension,
2-dysrhythmia,
3-coronary artery heart disease and
4-migraine.

Question 2

Mechanism of toxicity:

Answer 2

beta-receptor specificity is lost in overdose.

Question 3

Beta-receptor blockade inhibits

Answer 3

adenylate cyclase and decreases cAMP → decreased influx of sodium and calcium ions → negative inotropic and chronotropic effects.

Question 4

Propranolol has in addition

Answer 4

type I antidysrhythmic activity (membrane stabilizing activity)

Question 5

Sodium channel blockade (quinidine-like action)

Answer 5

→ wide QRS → ventricular dysrhythmias (This the greatest cause of morbidity)

Question 6

Propranolol has High degree of lipid solubility this increases

Answer 6

CNS penetration and results in CNS depression and convulsion.

Question 7

Clinical presentation

Answer 7

I-Cardiac disturbances,
-Bradycardia and asystole.
-Heart block.
-Hypotension,
-Cardiogenic shock, with severe overdose, especially with propranolol.
*The ECG usually shows
-Increased PR intervals; and HB
-QRS widening occurs with propranolol.
II-CNS toxicity,:
-convulsions, coma, and respiratory arrest, is commonly seen with propranolol.
III-Hypoglycemia (interference with glycogenolysis and gluconeogenesis)..
IV-Hyperkalemia (inhibits CA-mediated K uptake at skeletal muscle.)
V- Bronchospasm in asthmatic patients.

Question 8

Investigations

Answer 8

• ECG and cardiac monitoring.
• Serum electrolytes, especially K+ level.
• Serum glucose
• ABG.
• Renal function tests.
• Cardiac enzymes.

Question 9

Treatment

Answer 9

I- Emergency measures: ABCD
II- GI decontamination
*GL may be beneficial if the patient presents to the ED within 1-2 h of ingestion. Pre-treat with atropine to avoid severe bradycardia.
*AC should be administered routinely after lavage.

Question 10

Antidote

Answer 10

(Glucagon)
Action: Glucagon is a polypeptide hormone that stimulates the formation of adenyl cyclase, which in turn increases the intracellular concentration (cAMP). This results in positive inotropic, chronotropic effects. These effects occur independently of beta-adrenergic stimulation (glucagon has a separate receptor on the myocardium).

Question 11

Treatment of complications:

Answer 11

• Hypotension and bradycardia:
• Atropine.
• Glucagon.
• Calcium IV.
• Wide QRS ,ventricular dysrhythmias (propranolol): NaHCO3 IV
• Seizures:
• If caused by hypoglycemia: Glucose IV
• If caused by direct CNS effect (propranolol): BDZ