Question

What is the mechanism of action and common side effects of dobutamine, norepinephrine, labetalol, and amiodarone?

Answer 1

Dobutamine

A beta agonist catecholamine that has cardiac stimulant action without working vasiconstrictionnor tachycardia.

Mechanism if Action

Dobutamine is used as a phamacological agent because of it's ianotropic effects on the myocardium through binding and activating the beta - 1 receptors .Dobutamine increases contractility ,which leads to increased end systolic volume and therefore increased stroke volume.The larger stroke volume leafs to an increase in cardiac output of the heart .The changes in the cardiac output allows for the baroreceptor mediated response to decrease the systemic vascular resistance and cause little to no change in the arterial blood pressure.In addition dobutamine has shown to have beta -2 activity which contributes to the reduction in the systemic vascular resistance .

Side effects

Most frequent side effects:-

Increases heart rate

Increased blood pressure

Irregular ventricular beats

Chest Pain

Serious side effects includes:-

Low blood orespres

Chest Pain

Abnormal heart beat

Eosinophilic myocarditis

Norepinephrine

  Norepinephrine is an endogenous catecholamine synthesized in adrenal medulla that is the biochemical precursor of epinephrine.

Mechanism of Action

Norepinephrine functions as a peripheral vasocostrictor by stimulating alpha-1 and alpha -2 adrenergic receptors It is act as an ianotropic stimulator of heart and dialator of coronary artery by the activity of Beta 1 adrenergic receptors.

Side effects

Common side effects includes :-

Headache, nausea, vomiting

Infrequent side effects:-

Fast heart beat

High blood pressure

Ventricular arrythmias

Muscle tremors

Heart throwing and pounding

Rare side effects includes:-

Angina

fluid in lungs

blurredvision

High Blood pressure

Labetalol

Mode of Action

Labetalol non selectively antagonizes beta adrenergic receptors.and selectively antagonizes alpha-1 adrenergic receptors .Antagonism of alpha-1 adrenergic receptors leads to vasodialation and decreased vascular resistance.This leads to a decrease in blood pressure .Antagonism.of beta -1adrenerguc receptors leads to a slight decrease in heart rate.Antaginidm of Beta -2 adrenergic receptors leads to some side effects of labetalol such as bronchospasm however this may be attenuated by alpha- 1 .adrenergic antagonism.Labetalol leads to sustained vasodialation over long term without decrease in cardiac output or stroke volume and minimsl decrease in heart rate.

Side effects

Common:- Dizziness, Nausea, Tiredness

Serious. :- Bradycardia ( which will be presented as dizziness, lght headedness, fainting, fatigue)

Low Blood pressure

Liver damage ( dark colored urine, loss of appetite ,itiching)

Heart failure( shortness of breath ,chronic coughing,wheezing)

Breathing problems like shortness of beath.

Amiodarone

Amiodarone is considered as class lll anti arrhythmic drug.It blocks potassium currents that causes repolarization of the heart muscle during the third phase of cardiac action potential.As a result ,it increases the duration of action potential as well as the effective refractory period for cardiac cells ( myocytes) . Therefore cardiac muscle cell excitability is reduced,preventing and treating abnormal heart rhythm.Amiodarone also interferes with functioning of Beta adrenergic receptors ,sodium channels and calcium channrls .This action at times can lead to desirable effects of hypotension ,Bradycardia.Amiodarone has been found to bind to thyroid receptors due to it's iodine content ,potenti pote leading to amiodarone induced hypothyroidism or thyrotoxicosis.

Side effects

Increased liver AST or ALT levels

Low Blood pressure

Dizziness

Abnormal Gait/ problem with coordination

Involuntary movements

Hypothyroidism

Sleep disturbances

SA node dysfunction

Hepatitis, Cirrhosis

Optic neuritis

Corneal micro deposits

Congestive cardiac failure

ARDS

Constipation.