Epinephrine, also widely known as adrenaline, is a powerful hormone and medication that plays
a crucial role in the body's "fight-or-flight" response. It is naturally produced by the adrenal
glands and certain neurons.
What it is and does:
● Hormone and Neurotransmitter: Epinephrine acts as both a hormone (released into the
bloodstream) and a neurotransmitter (chemical messenger in the nervous system).
● Fight-or-Flight Response: When the body perceives a threat, epinephrine is released,
triggering a cascade of physiological changes to prepare for action. This includes:
○ Increased heart rate and force of contraction: To pump blood more efficiently.
○ Bronchodilation: Widening of airways in the lungs to allow for deeper and faster
breathing.
○ Vasoconstriction in some areas, vasodilation in others: Blood is diverted from
less critical areas (like skin and digestive tract) to vital organs (like muscles and
brain). This helps maintain blood pressure.
○ Pupil dilation: To enhance vision.
○ Breakdown of glycogen in the liver: To release glucose for energy.
● Mechanism of Action: Epinephrine exerts its effects by binding to and activating alpha
(α) and beta (β) adrenergic receptors throughout the body. The specific effects depend on
the type of receptor and its location, as well as the dose. Low doses tend to primarily
activate β-receptors, while higher doses engage α-receptors more significantly.
Medical Uses:
Epinephrine is a life-saving medication used in various emergency situations:
● Anaphylaxis (severe allergic reactions): This is perhaps its most well-known use.
Epinephrine rapidly reverses symptoms like difficulty breathing, swelling, hives, and
dangerously low blood pressure caused by allergic reactions to insect stings, foods,
medications, etc. It's often administered via auto-injectors (like EpiPen).
● Cardiac Arrest/Cardiopulmonary Resuscitation (CPR): It stimulates the heart and
helps increase blood pressure during cardiac arrest.
● Septic Shock: Used to manage dangerously low blood pressure associated with severe
body-wide infections.
● Severe Asthma Exacerbations: It helps open airways and reduce spasms when
standard treatments are ineffective.
● Croup: Can be used to alleviate respiratory distress in severe cases.
● As a local anesthetic additive: Used to prolong the action of local anesthetics and
reduce bleeding at the injection site due to its vasoconstrictive properties.
● During intraocular surgeries: To induce and maintain mydriasis (pupil dilation).
Side Effects:
While epinephrine is crucial in emergencies, it can have side effects, especially at higher doses
or in sensitive individuals. Common side effects include:
● Tachycardia (rapid heartbeat)
● Palpitations (feeling your heart beat fast or irregularly)
● Hypertension (high blood pressure)
● Anxiety, apprehension, restlessness, nervousness
● Tremors or shaking
● Dizziness
● Sweating
● Nausea and vomiting
● Headache
● Pale skin
● Weakness
More serious, though less common, side effects can include chest pain, stroke, or heart attack,
particularly in individuals with underlying cardiovascular conditions. It's vital to seek immediate
medical attention after administering epinephrine for an emergency, as medical professionals
can monitor and manage any potential side effects.
