catecholamines

Question 1

general catecholamines

Answer 1

Catecholamines are the strongest sympathomimetics, but they can’t
be given orally, they have a short duration of action, and they don’t
penetrate the blood-brain barrier.

Question 2

epinephrine

Answer 2

beta&raquo_space; alpha
• The mean arterial pressure is not changed dramatically (systolic raised, diastolic slightly depressed)
• It has positive inotropic and chronotropic actions on the heart.
• It causes bronchodilation.
it causes hyperglycemia and lipolysis

• Indications:
• anaphylactic shock (0.3-0.5 mg sc. or im.)
• emergency managem
ent of complete heart block and cardiac arrest (1 mg iv.) • asthmatic state
• inhaled epinephrine – treatment of croup (subglottic laryngitis)
• reduction of regional blood flow
• local anaesthesia (1:200,000 - combination with local anaesthetics)
• facial, nasopharyngeal, oral surgery

side-affects: Pulmonary edema, hemorrhage, CNS disturbances (anxiety, fear, tension and headache), cardiac arrhythmias.

Interactions: hyperthyroidism (reduce epinephrine given), DM (might have to increase insulin given) concaine, Beta blockers and inhalation anesthetics (sensitize heart to epinephrine effect).

Question 3

norepinephrine, also called levarterenol in practice.

Answer 3

• Norepinephrine activates α and β1 receptors, but it
has a little effect on β2 receptors.
• It causes vasoconstriction, and elevates the blood
pressure (both systolic and diastolic increase).
• Compensatory vagal reflexes can overcome its direct
positive chronotropic action on the heart. (It may cause
bradycardia in vivo.)

• Indications:
• neurogenic shock (early phase), septic shock, cardiogenic shock (pressor effect in case of hypotensive emergency)
• locally to reduce blood flow (diffuse bleeding; combination
with local anaesthetics)

Question 4

isoproterenol

Answer 4

• Isoprenaline is a potent and selective β receptor
agonist (both β1 and β2).
• It has positive inotropic and chronotropic actions
on the heart.
• It causes vasodilation, greatly decreases the diastolic and the mean arterial pressure. but increases CO!
• It causes bronchodilation.
• Possible indications:
• Bradycardia, heart blocks (AV)

Question 5

dopamine

Answer 5

In low dose (0.5-2.5 μg/kg/min) it activates D1 dopamine
receptors selectively (vasodilation – increased renal blood flow)

• In addition, in medium dose (2.5-5 μg/kg/min) it activates β1 adrenergic receptors (positive inotropic action on the
heart)

• In high dose (more than 5 μg/kg/min) it looses the
selectivity, acts like epinephrine.

• Indication: drug of choice for septic and cardiogenic shock (low to medium dose) due to preservation of renal blood flow and prevention of kidney ischemia.
also used for CHF and hypotension
• Problems: tachycardia, tolerance, bad pharmacokinetics

Question 6

dobutamine

Answer 6

• it causes less tachycardia compared with dopamine

Question 7

fenoldopam

Answer 7

beta agonist
• peripheral vasodilation in mesenterial vascular bed
• administered i.v. for the treatment of severe hypertension

Question 8

dopexamin

Answer 8

•D, β2(β1) agonist, (reuptake inhibitor)