A Guide to Dopamine and Epinephrine

SimpleNursing Editorial Team Aug 24, 2018
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As a nursing student, it’s crucial to familiarize yourself with emergency drugs commonly used in healthcare settings. Dopamine and epinephrine are two medications frequently employed in emergency situations to stabilize patients and manage life-threatening conditions.

Jump to Sections

  1. Dopamine Pharmacology
  2. Epinephrine Pharmacology
  3. A Different Approach to Emergency Drugs

Dopamine and epinephrine are vital emergency drugs that nursing students should be familiar with. Understanding these medications’ mechanisms of action, indications, administration routes, and potential side effects is essential for providing safe and effective care to patients in critical situations. 

Dopamine Pharmacology

Dopamine is a catecholamine neurotransmitter used to treat hemodynamic imbalances, poor perfusion of vital organs, low cardiac output, and hypotension.

Dopamine is one of the catecholamine neurotransmitters in the brain. It’s derived from tyrosine and is the precursor to norepinephrine and epinephrine. Dopamine is also a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. It’s considered an inotropic drug because it helps with forceful heart contractions.

Dopamine Mechanism of Action

Dopamine is a neurotransmitter that acts on various receptor subtypes in the central nervous system and peripheral tissues. Its mechanism of action depends on the receptor it interacts with:

  • D1-like receptors: Activation of D1-like receptors (D1 and D5) leads to an increase in intracellular cyclic adenosine monophosphate (cAMP) levels through stimulation of adenylyl cyclase. This pathway is involved in vasodilation, increased renal blood flow, and natriuresis (excretion of sodium in the urine).
  • D2-like receptors: Activation of D2-like receptors (D2, D3, and D4) inhibits adenylyl cyclase, decreasing cAMP levels. This pathway is associated with various effects, including motor function regulation, hormone release modulation, and control of mood and emotions.

Dopamine Indications

Dopamine is usually given to patients who are extremely hypotensive (low blood pressure) to facilitate the proper flow of oxygen. Since oxygen is vital to life, extremely low blood pressure can be detrimental because oxygen is not appropriately distributed to different body areas. Dopamine is helpful in this situation.

Dopamine as an Inotropic Drug

Not all drugs are negative chronotropic. Dopamine is an inotropic drug that increases the heart rate to increase blood pressure and oxygen perfusion. The goal is to increase the amount of oxygen in the red blood cells, specifically the hemoglobin, to carry them out to different body parts.

Digoxin vs. Dopamine

Digoxin is also an inotropic drug; however, it is more focused on atrial fibrillation, specifically targeted on the atrial kick. As for dopamine, it is more on perfusion. By being a vasopressor, dopamine presses on the veins to bring blood back to the heart and push oxygenated blood out to the rest of the body.

Digoxin Mechanism of Action

Digoxin is used primarily in the treatment of heart failure and certain arrhythmias. Its mechanism of action involves the inhibition of the sodium-potassium ATPase pump (Na+/K+-ATPase) in cardiac myocytes. 

The Na+/K+-ATPase normally maintains the balance of sodium and potassium ions, which is essential for proper cardiac function. By inhibiting this pump, digoxin increases intracellular calcium levels, leading to increased contractility of the heart muscle. It also indirectly affects the autonomic nervous system and helps regulate heart rate.

Epinephrine Pharmacology

Dopamine and epinephrine are similar but different. How?

Epinephrine has some of the same qualities as dopamine with a positive inotropic effect, which helps the heart contract. Epinephrine also has a positive chronotropic effect in increasing the heart rate. Lastly, epinephrine is also known as adrenaline, a sympathomimetic drug miming the sympathetic nervous system.

The Sympathomimetic Response (Fight and Flight)

A sympathomimetic response or a fight and flight response is when the body increases the heart rate to increase blood flow to the heart, lungs, and brain. However, with epinephrine, it’s done differently – there is no pressure acting on the vessels to increase perfusion. Instead, epinephrine acts like a hormone that stimulates the fight and flight response.

This approach is just one of many different routes, and is useful and effective in bringing the heart rate up and contracting more forcefully.

Epinephrine Mechanism of Action

Epinephrine is a hormone and neurotransmitter that plays a crucial role in the body’s response to stress and emergency situations. Its mechanism of action involves binding to adrenergic receptors, specifically the alpha and beta-adrenergic receptors, located on various tissues throughout the body. Epinephrine acts as a potent agonist at these receptors, leading to several physiological effects:

  • Beta-1 adrenergic receptors: Stimulation of beta-1 receptors increases heart rate and force of contraction, resulting in increased cardiac output.
  • Beta-2 adrenergic receptors: Activation of beta-2 receptors causes smooth muscle relaxation in the bronchioles, blood vessels, and uterus. This leads to bronchodilation, vasodilation, and inhibition of uterine contractions.
  • Alpha-adrenergic receptors: Stimulation of alpha receptors causes vasoconstriction, which can help increase blood pressure and reduce bleeding in certain situations.

A Different Approach to Emergency Drugs

Giving emergency drugs is like being locked out of the house; there are a couple of ways to go in, and you will still get the same result of being able to get in. Whether you’re trying to decrease blood pressure or heart rate, it can be done with the ABC drugs. 

On the other hand, if the goal is to increase the pressure, heart rate, and perfusion, you can choose from inotropic, chronotropic, and dromotropic drugs.

Prepare for Success in Your Pharmacology Exams and Beyond

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