الحلقة 11 من كورس كلنيكال فارما (ANS)

Continue Non-selective Direct acting

Norepinephrine (NE) or Noradrenaline (NA) (Levophed®)

About

The drug

- Norepinephrine is a naturally catecholamine.

- Secreted from adrenal medulla 20%.

- Act on α receptors more than β receptors.

- It is given IV for rapid onset of action.

- The duration of action is 1 to 2 minutes.

- It is rapidly metabolized by MAO and COMT, and

inactive

metabolites are excreted in the urine.

CVS

Actions

1)Vasoconstriction Effect:

- Norepinephrine causes greater vasoconstriction effect

than epinephrine (because it does not induce

compensatory vasodilation via β2 receptors on blood

vessels supplying skeletal muscles).

-↑ peripheral resistance (PR) due to intense

vasoconstriction. -↑ both systolic and diastolic blood

pressures.

2) Baroreceptor reflex:

- Norepinephrine ↑ blood pressure → stimulates baroreceptors

↑ vagal activity→ reflex bradycardia.

- Reflex bradycardia can blocked by administration of atropine

(blocks the transmission of vagal effects) before norepinephrine.

Therapeutic

Uses

-Used as a vasopressor in treatment vasodilatory shock (acute

severe hypotension such as in septic shock).

-It has no other clinically significant uses, because weak β2

activity of norepinephrine.

Side

effects

- CNS effects: anxiety and headache.

- CVS effects: hypertension, local VC, tissue hypoxia and reflex

bradycardia.

- Local effects: Blanching along the site of the infused vein (due to

potent vasoconstrictor effects) with ↑ venous permeability lead

to extravasation (leakage of drug from the vessel into tissues

surrounding the injection site)→ lead to local tissue necrosis and

rarely tissue sloughing.

Isoproterenol or Isoprenaline or Isopropyl noradrenaline (Isuprel®)

About

The drug

-Isoproterenol is a synthetic catecholamine.

-Stimulates both Bi and B2 receptors (insignificant activity on a

receptors).

- It is rarely used therapeutically due to non-selectivity.

Pharmacological

Action

• Heart --- increase heart rate, force of contraction and

cardiac output → moderate increase systolic pressure

(B1).

• Skeletal muscle → dilate arterioles →decrease

peripheral resistance →marked decrease diastolic

pressure (B2).

• Bronchi →potent bronchodilator effect (B2).

Therapeutic

Uses

- Heart attack and certain types of irregular heartbeat (heart

block).

- Acute attack of bronchial asthma.

- N.B:

- The use of isoproterenol has largely been replaced with other

drugs.

Side effects: similar to those of epinephrine.

Dopamine (DA) (Intropin®)

About

The drug

-Dopamine is a naturally catecholamine.

-In the brain, dopamine functions as a neurotransmitter and

plays a number of important roles as well as in the outside the

brain.

- It is rapidly metabolized by MAO or COMT.

- It is can activate α- and β-adrenergic receptors as well as

dopaminergic receptors.

* In small dose → activate D-dopaminergic receptors.

* In moderate dose → activate β-adrenergic receptors.

* In high dose activate on α-adrenergic receptor.

Pharmacological

Action

- Cardiac stimulatory effects:

(+ve) inotropic and chronotropic effects→ β1

- At very high doses (Vasoconstrictor effects):

Vasoconstriction → α1.

- Dilates renal blood vessels:

Increase blood flow to the kidneys→ D1

Therapeutic

Uses

1.Cardiogenic and septic shock: (by continuous infusion)

➢ A blood pressure {1 CO (β1) and ↑ PR (α1)}.

➢ ↑ perfusion to thể kidney (D1) →↑ glomerular

filtration rate → diuresis.

N.B: First researchers suggest; the dopamine used as first-line

choice for shock, (particularly septic shock), but recently;

norepinephrine became the drug of first choice because;

dopamine causes arrhythmia and has high mortality rate. –

2.Hypotension and severe heart failure: primarily

- In patients with low or normal peripheral vascular

resistance.

-In patients who have oliguria (low urine output).

Side effects - Tachycardia. hypertension, nausea, vomiting and headache.

Dopexamine (Dopacard®)

About

the drug

-It Is a synthetic analogue of dopamine, it stimulate D1 and β1

receptors (not dose dependant).

-It is rapidly eliminated from blood.

-Uses and side effects same as dopamine      

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