Adrenaline it's mechanism indications contraindications how to give how to dilute dose

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epinephrine anaphylaxis dosing

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Adrenaline (Epinephrine)

Mechanism of Action

Epinephrine is an endogenous catecholamine that acts as a nonselective agonist at α1, β1, and β2 adrenergic receptors:

α1 effects: peripheral vasoconstriction → increases systemic vascular resistance, raises diastolic BP, improves coronary and cerebral perfusion pressure. Also reduces mucosal edema and mast cell mediator release (key in anaphylaxis).
β1 effects: increased heart rate and myocardial contractility → increased cardiac output.
β2 effects: bronchial smooth muscle relaxation (bronchodilation) and stabilization of mast cells/basophils, reducing histamine release.

Onset is rapid (1-2 min) with a short duration of action (2-10 min); it is metabolized hepatically by MAO and COMT (Tintinalli's Emergency Medicine; Miller's Anesthesia, 10e; Current Surgical Therapy, 14e).

Indications

Anaphylaxis - first-line, life-saving treatment (Dermatology 2-Vol Set, 5e)
Cardiac arrest - VF/pulseless VT unresponsive to shock, asystole, PEA
Symptomatic bradycardia unresponsive to atropine or transcutaneous pacing
Septic shock - as an additional vasopressor when norepinephrine alone is insufficient
Cardiogenic shock / low cardiac output states
Severe bronchospasm/asthma unresponsive to standard therapy
Croup / upper airway edema - nebulized route
Local hemostasis and prolongation of local anesthetic action (added to lidocaine, etc.) (Tintinalli's Emergency Medicine; Red Book 2021; Bailey and Love's Short Practice of Surgery)

Contraindications / Cautions

There is no absolute contraindication in true anaphylaxis - it remains life-saving regardless of comorbidities. However, caution/relative contraindication applies to:

Patients on monoamine oxidase inhibitors (MAOIs) - should not receive epinephrine-containing preparations
Tricyclic antidepressants and pre-existing cardiovascular disease - contraindicated for epinephrine-containing local anesthetics
Hyperthyroidism, uncontrolled hypertension, atherosclerotic cardiovascular disease - use with caution
Narrow-angle glaucoma
Local infiltration in fingers, toes, penis, nose, ears or areas with poor vascular supply, and caution in diabetes/peripheral vascular disease (end-arteriole ischemia risk)
IV administration risks lethal arrhythmia - cardiac monitoring required; avoid mixing with alkaline solutions (inactivates the drug)

(Bailey and Love's Short Practice of Surgery, 28e; Pfenninger and Fowler's Procedures for Primary Care, 3e)

How to Give (Route)

IM (anterolateral thigh) - preferred first-line route for anaphylaxis; can repeat at the same injection site if the reaction followed an injected allergen (slows systemic absorption of the trigger)
IV bolus - reserved for cardiac arrest or anaphylaxis refractory to IM dosing, given slowly with cardiac monitoring
IV continuous infusion - for refractory anaphylaxis, cardiogenic shock, or septic shock requiring titration
Nebulized - for croup/laryngeal edema
Subcutaneous infiltration - combined with local anesthetics for hemostasis/prolonged block

Dilution

Preparation	Concentration	Typical use
1:1000	1 mg/mL	IM injection (anaphylaxis), nebulization, local infiltration
1:10,000	0.1 mg/mL	IV/IO bolus (cardiac arrest, refractory anaphylaxis) - made by diluting 1 mL of 1:1000 in 9 mL 0.9% saline
Infusion	1 mg in 250 mL D5W/NS = 4 microg/mL (or 2 mg in 100 mL = 20 microg/mL)	Continuous IV infusion

Do not mix epinephrine into alkaline IV solutions.

Doses

Anaphylaxis (IM, 1:1000):

0.01 mg/kg (0.01 mL/kg), up to a maximum single dose of 0.5 mL (0.5 mg), IM in the anterolateral thigh
Repeat every 5-15 minutes as needed, up to 3 doses if not responding

Anaphylaxis refractory to IM (IV, 1:10,000):

0.01 mg/kg (0.1 mL/kg) as a slow IV bolus, with cardiac monitoring

Continuous IV infusion (anaphylaxis/cardiogenic shock):

1 mg (1 mL of 1:1000) in 250 mL D5W = 4 microg/mL, start at 0.1 microg/kg/min, titrate up to 1 microg/kg/min to maintain BP
General vasoactive dosing range cited in surgical literature: 0.01-0.4 microg/kg/min

Cardiac arrest (IV/IO):

1 mg of the 1:10,000 dilution (10 mL) IV/IO every 3-5 minutes; no maximum cumulative dose
High-dose epinephrine (2-5 mg) is not recommended - associated with worse neurologic outcomes without survival benefit

Nebulized (croup/laryngeal edema):

1 mL of 1:1000 diluted in 3 mL of 0.9% saline

Sources: Tintinalli's Emergency Medicine; Red Book 2021 (AAP Committee on Infectious Diseases); Miller's Anesthesia, 10th ed; Current Surgical Therapy, 14th ed; Bailey and Love's Short Practice of Surgery, 28th ed; Dermatology 2-Volume Set, 5th ed; Pfenninger and Fowler's Procedures for Primary Care, 3rd ed.

A quick check of recent systematic reviews/meta-analyses (2024-2025) on anaphylaxis and epinephrine dosing did not surface any findings that contradict these standard doses/routes - current guidance remains consistent with the textbook recommendations above.

In easy way

Adrenaline (Epinephrine) - Simple Explanation

What it does (Mechanism)

Adrenaline is a natural hormone that:

Tightens blood vessels → raises blood pressure
Speeds up the heart → pumps more blood
Opens up airways → helps breathing
Calms down allergic reactions → stops the body from releasing more allergy chemicals

Think of it as the "fight or flight" hormone - it kicks the heart, lungs, and blood vessels into high gear.

When to use it (Indications)

Severe allergic reaction (anaphylaxis) - swelling, difficulty breathing, low BP - #1 use
Cardiac arrest - heart has stopped
Very slow heart rate that isn't responding to other drugs
Severe asthma attack that isn't improving
Septic shock / low BP as a backup drug
Croup (child's airway swelling) - given as inhaled mist
Mixed with local anesthetic (like at the dentist) to reduce bleeding and make numbness last longer

When to be careful (Contraindications)

In a true severe allergy reaction → always give it, no exceptions, it's life-saving
Be cautious in people with heart disease, high blood pressure, or overactive thyroid
Don't give with certain antidepressants (MAOIs)
Don't inject into fingers, toes, nose, ears, or penis (can cut off blood supply there)
Watch the heart closely if giving through a vein (can cause dangerous fast heart rhythms)

How to give it

Allergic reaction → injection into the outer thigh muscle (like an EpiPen)
Heart attack/cardiac arrest → injection into a vein
If very sick and needs a steady effect → slow drip through a vein (IV infusion)
Croup/breathing swelling → breathed in through a nebulizer mask

How to dilute and dose (simple version)

For allergic reaction (IM shot):

Use the strong solution (1:1000 = 1 mg per mL)
Dose: 0.01 mg per kg of body weight, max 0.5 mg per shot
Can repeat every 5-15 minutes, up to 3 times

For cardiac arrest (IV push):

Dilute it weaker first (1:10,000 = 0.1 mg per mL) - mix 1 mL of the strong stuff with 9 mL saline
Give 1 mg every 3-5 minutes, no upper limit

For a slow drip (infusion):

Mix 1 mg of adrenaline in 250 mL of fluid (makes it very dilute, 4 micrograms per mL)
Start slow and increase gradually while watching blood pressure

Simple rule to remember: stronger solution (1:1000) for muscle shots, weaker solution (1:10,000) for vein injections.

Dopamine doubtamine adrenaline digoxin it mechanism and dose indications contraindications how to give how munch to dilute in table form in easy wording

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Easy Comparison Table: Adrenaline, Dopamine, Dobutamine, Digoxin

	Adrenaline (Epinephrine)	Dopamine	Dobutamine	Digoxin
What it is	Natural "fight or flight" hormone	Natural hormone, precursor of adrenaline	Man-made (synthetic) heart drug	Plant-derived heart drug (from foxglove)
Mechanism (simple)	Acts on α and β receptors → tightens blood vessels, speeds up heart, opens airways	Dose-dependent: low dose → opens kidney/gut vessels; medium dose → strengthens heart beat; high dose → tightens blood vessels like adrenaline	Mainly acts on heart (β1) → makes heart pump stronger and faster; mild vessel-opening effect	Blocks a heart cell pump (Na+/K+-ATPase) → more calcium stays in the cell → heart beats stronger, and slows the electrical signal through the AV node (slows heart rate)
Main job	Vasoconstrictor + bronchodilator + heart stimulant	Blood pressure / cardiac output support	Boosts a weak heart's pumping strength	Strengthens weak heart beat + slows fast heart rate in AFib
Indications	- Severe allergy (anaphylaxis) - Cardiac arrest - Very slow heart rate not responding to atropine - Septic shock (add-on) - Severe asthma - Croup (nebulized)	- Shock with low blood pressure (esp. cardiogenic/septic) - Symptomatic bradycardia as backup	- Heart failure with poor pumping (low cardiac output) - Cardiogenic shock - Used in "dobutamine stress echo" test	- Heart failure with reduced pumping (add-on, not first choice) - Atrial fibrillation (to control fast heart rate)
Contraindications / Caution	- Careful with MAOI drugs, tricyclic antidepressants - Caution in heart disease, high BP, overactive thyroid - Don't inject into fingers/toes/nose/ears/penis	- Caution in fast irregular heart rhythms (can worsen) - Avoid in pheochromocytoma - Watch for tissue death if it leaks outside the vein	- Caution in outflow obstruction (like severe aortic stenosis, HOCM) - Can trigger irregular heart beats - Less effective if patient is on beta-blockers	- Very narrow safety margin - toxic levels close to treatment levels - Avoid/adjust dose in kidney problems (drug builds up) - Low potassium makes toxicity worse - Caution with heart block
How to give (route)	IM injection (thigh) for allergy; IV push for cardiac arrest; slow IV drip for shock; inhaled for croup	Always given as a slow continuous IV drip (never as a single push) - needs a working IV line, ideally a big vein	Given as a slow continuous IV drip through a pump	Oral tablets for daily use; IV given slowly for urgent situations
Dilution (how much to mix)	Strong form 1:1000 (1 mg/mL) for IM shots. Weaker form 1:10,000 (0.1 mg/mL) for IV push - made by adding 1 mL of the strong solution to 9 mL saline. Drip: 1 mg in 250 mL fluid = 4 microgram/mL	Typically 400 mg mixed in 250 mL fluid (about 1600 microgram/mL)	Typically 250 mg mixed in 250 mL fluid (about 1000 microgram/mL), or per hospital protocol	No dilution needed for tablets. IV form is given slowly, undiluted or per hospital protocol, over several minutes
Dose	Allergy (IM): 0.01 mg/kg, max 0.5 mg, repeat every 5-15 min (up to 3 times) Cardiac arrest (IV): 1 mg every 3-5 min Drip: start 0.1 microgram/kg/min, titrate up	1-3 microgram/kg/min = mild ("kidney dose") 3-8 microgram/kg/min = stronger heart beat Above 10 microgram/kg/min = mainly vessel-tightening	Usual range 2-20 microgram/kg/min, start low and increase slowly while watching blood pressure and heart rhythm	Heart failure: usually 0.125 mg once daily (lower in kidney disease/elderly) AFib loading (if urgent): larger initial dose split over first day, then daily maintenance dose

Quick memory tips

Adrenaline = the emergency "rescue" drug (allergy, cardiac arrest)
Dopamine = dose changes what it does (low = kidneys, high = vessel squeeze)
Dobutamine = the "pure pump booster" for a weak heart, doesn't squeeze vessels much
Digoxin = old, slow-acting heart helper, dangerous if too much builds up (watch potassium and kidneys)

Sources: Lippincott Illustrated Reviews Pharmacology; Braunwald's Heart Disease, 2-Vol Set; Fischer's Mastery of Surgery, 8th ed; Tintinalli's Emergency Medicine; Current Surgical Therapy, 14th ed; Red Book 2021.

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