Emergency Drugs: Adrenaline, Vasopressors, Antidotes

Emergency drugs are the small set of powerful medicines given in the first minutes of cardiac arrest, anaphylaxis, shock and poisoning, when each passing minute lowers survival. Adrenaline (epinephrine) restarts the circulation by constricting blood vessels and stimulating the heart; vasopressors like noradrenaline hold blood pressure up in septic shock; and antidotes like naloxone and N-acetylcysteine directly reverse specific poisons. They are given by fixed protocols, not by trial and error.

This matters because cardiac arrest survival falls with every minute without adrenaline and defibrillation, anaphylaxis can kill within minutes without intramuscular adrenaline, and paracetamol poisoning destroys the liver silently unless its antidote is started in time.

Key Concepts

• Adrenaline: stimulates alpha receptors (vessel constriction) and beta receptors (stronger faster heartbeat, open airways); the single most important emergency drug.
• Concentrations: 1:1000 means 1 mg per mL (for intramuscular use); 1:10000 means 0.1 mg per mL (for intravenous use in arrest).
• Anaphylaxis dose: 0.3 to 0.5 mg of 1:1000 adrenaline intramuscularly into the outer thigh, repeatable every 5 to 15 minutes.
• Cardiac arrest dose: 1 mg of 1:10000 adrenaline IV every 3 to 5 minutes during resuscitation.
• Noradrenaline: first-line vasopressor in septic shock, infused at 0.05 to 0.6 micrograms per kg per minute.
• Supportive agents: atropine 1 mg IV for symptomatic bradycardia (maximum 3 mg); amiodarone 300 mg IV for shock-resistant ventricular fibrillation; dobutamine when the heart needs squeezing power rather than vessel tone.
• Antidotes: naloxone 0.4 to 2 mg IV reverses opioid overdose; flumazenil reverses benzodiazepines (used cautiously); N-acetylcysteine replenishes glutathione in paracetamol poisoning; activated charcoal binds ingested poisons if given within 1 to 2 hours.

Formulas

• 1:1000 adrenaline: 1 mg per mL; volume in mL equals the dose in mg.
• 1:10000 adrenaline: 0.1 mg per mL; volume in mL equals ten times the dose in mg.

Worked Example

A patient collapses with anaphylaxis after a bee sting, then a second patient arrests in the next bay. Case 1: the doctor orders 0.5 mg adrenaline IM. Using 1:1000 (1 mg per mL), volume = 0.5 mg divided by 1 mg per mL = 0.5 mL, injected into the anterolateral thigh; it may be repeated in 5 minutes if the blood pressure has not recovered. Case 2: the arrested patient needs 1 mg IV. Using 1:10000 (0.1 mg per mL), volume = 1 mg divided by 0.1 mg per mL = 10 mL IV push, repeated every 3 to 5 minutes.

Common Misconceptions

• "IV adrenaline works faster in anaphylaxis, so give it IV first." Intramuscular adrenaline in the thigh is first-line; IV bolus adrenaline in anaphylaxis risks fatal arrhythmia and is reserved for peri-arrest cases given as a careful infusion.
• "Keep pushing more adrenaline and the heart will restart." Beyond protocol doses, extra adrenaline worsens heart oxygen demand and brain injury; high-quality chest compressions and defibrillation matter more than extra drug.
• "An antidote fixes poisoning by itself." Antidotes buy time; airway protection, fluids, seizure control and monitoring remain the foundation,

Real-World Applications

• Anaphylaxis kits: adrenaline auto-injectors (0.3 mg adult, 0.15 mg child) carried by people with severe allergies.
• Intensive care: noradrenaline infusions as the backbone of septic shock management.
• Emergency departments: naloxone for opioid overdose, now also available as a nasal spray for bystanders.
• Poison control: N-acetylcysteine within 8 hours of paracetamol overdose prevents liver failure.

Adrenaline saves lives in anaphylaxis at 0.5 mg intramuscularly of 1:1000 and in cardiac arrest at 1 mg intravenously of 1:10000, noradrenaline sustains pressure in shock, and antidotes reverse specific poisons. Concentration math must be automatic because the wrong syringe kills.