Essential Paramedic Pharmacology Revision Guide

Why Pharmacology Matters in Paramedic Practice

Pharmacology sits at the heart of paramedic practice. Whether you are managing a patient in anaphylaxis, controlling a seizure, or providing pain relief at a road traffic collision, your ability to select, prepare, and administer the right drug safely can be the difference between life and death. For UK student paramedics, building a confident and detailed understanding of drugs — from their mechanisms of action to their contraindications — is non-negotiable.

This revision guide is designed to give you a structured overview of the key pharmacological principles and drug groups you need to know, grounded in the JRCALC (Joint Royal Colleges Ambulance Liaison Committee) guidelines used across NHS ambulance services in the UK.

Core Pharmacological Principles

Before diving into individual drug classes, you must be comfortable with the underpinning theory. These concepts apply to every drug you will ever administer.

Pharmacokinetics

Pharmacokinetics describes what the body does to a drug, summarised by the acronym ADME:

• Absorption: How the drug enters the systemic circulation. Route matters — IV administration bypasses absorption entirely, giving a faster, more predictable onset than oral or IM routes.
• Distribution: How the drug spreads through body tissues. Factors such as lipid solubility, protein binding, and the blood-brain barrier all influence distribution.
• Metabolism: Primarily hepatic. The cytochrome P450 enzyme system is responsible for breaking down many drugs. First-pass metabolism significantly reduces the bioavailability of oral drugs.
• Excretion: Mostly renal. Impaired kidney or liver function can dramatically alter drug clearance, increasing the risk of toxicity.

Pharmacodynamics

Pharmacodynamics describes what the drug does to the body. Most drugs exert their effects by binding to receptors, enzymes, or ion channels. Key receptor types you must know include adrenergic receptors (alpha-1, beta-1, beta-2), muscarinic and nicotinic receptors, and opioid receptors (mu, kappa, delta). Understanding agonist versus antagonist action is fundamental — for example, salbutamol is a beta-2 agonist, while naloxone is a pure opioid antagonist.

Key Drug Classes in Pre-Hospital Care

Analgesics

Pain management is one of the most frequent interventions a paramedic performs. The main analgesics used in UK pre-hospital practice include:

• Morphine: A potent opioid analgesic. Acts on mu-opioid receptors. Side effects include respiratory depression, nausea, and hypotension. Naloxone is the reversal agent.
• Methoxyflurane (Penthrox): An inhaled analgesic increasingly used in pre-hospital settings for moderate to severe pain. Fast onset, patient-controlled, and does not cause respiratory depression.
• Paracetamol (IV): Used for mild to moderate pain or as an adjunct. Safe profile makes it suitable for a wide range of patients including the elderly and those with contraindications to opioids.
• Entonox (50% nitrous oxide / 50% oxygen): Effective for short-duration analgesia. Contraindicated in pneumothorax, decompression sickness, and bowel obstruction.

Drugs Used in Cardiac Emergencies

Cardiovascular emergencies demand rapid, accurate drug administration. Key drugs include:

• Adrenaline (Epinephrine): First-line drug in cardiac arrest (1mg IV/IO every 3–5 minutes per ALS guidelines) and anaphylaxis (500 micrograms IM). Acts on alpha and beta adrenergic receptors.
• Amiodarone: Used in shockable rhythms (VF/pVT) after the third shock. 300mg IV bolus. Can cause hypotension and bradycardia.
• Aspirin: 300mg chewed, given in suspected ACS. Irreversibly inhibits COX-1, reducing platelet aggregation.
• GTN (Glyceryl Trinitrate): Sublingual spray used in chest pain and acute pulmonary oedema. Vasodilator — contraindicated if systolic BP is below 90mmHg or if the patient has taken a phosphodiesterase inhibitor.

Drugs Used in Respiratory Emergencies

• Salbutamol: Beta-2 agonist delivered via nebuliser or MDI. Causes bronchodilation. Used in asthma and COPD exacerbations. Tachycardia is a common side effect.
• Ipratropium bromide: Anticholinergic bronchodilator. Used alongside salbutamol in severe or life-threatening asthma. Works by blocking muscarinic receptors in the airways.
• Hydrocortisone: IV corticosteroid used in severe asthma and anaphylaxis. Anti-inflammatory effect has a delayed onset of 4–6 hours.

Drugs Used in Neurological Emergencies

• Midazolam (buccal): Benzodiazepine used as first-line treatment for prolonged seizures in adults and children. Enhances GABA activity, producing anticonvulsant and sedative effects.
• Diazepam (rectal): An alternative benzodiazepine for seizure management, particularly in paediatric patients.
• Glucose (oral or IV): Treatment for hypoglycaemia. Glucagon (IM) is used when IV access is not available.

Drug Calculation Essentials

Drug errors are a significant patient safety concern in pre-hospital care. You must be fluent in drug calculations, including:

• Weight-based dosing (mg/kg) — especially critical in paediatrics
• Concentration calculations (e.g., mg/mL to determine volume to draw up)
• Infusion rate calculations where relevant to your scope of practice

Practise these regularly under timed conditions to simulate exam and real-world pressure. Always double-check your calculations and, where possible, have a colleague verify them.

Revision Tips for Student Paramedics

Pharmacology can feel overwhelming given the volume of information, but structured revision makes it manageable. Try the following approaches:

1. Learn by drug class, not by individual drug: Understanding the class mechanism makes it easier to predict side effects and contraindications for all drugs in that group.
2. Use active recall: Cover your notes and try to recall indications, doses, contraindications, and side effects from memory. Flashcards work well for this.
3. Apply drugs to clinical scenarios: Rather than rote memorising, ask yourself — in which patient would I use this drug? What would stop me from using it?
4. Refer to JRCALC regularly: The JRCALC guidelines are your clinical bible. Cross-reference your university notes with JRCALC entries to ensure accuracy.
5. Test yourself under exam conditions: Practice MCQs and written questions within time limits to build the retrieval speed needed in assessments and OSCEs.

Contraindications and Special Populations

Always consider your patient holistically. Contraindications, allergies, renal or hepatic impairment, pregnancy, and age (particularly the elderly and paediatric patients) can all significantly alter drug choice and dosing. Paediatric drug doses are almost always weight-based — familiarise yourself with the Broselow tape and paediatric drug charts used by your trust.

Older patients are at higher risk of adverse drug reactions due to polypharmacy, reduced renal clearance, altered drug distribution, and increased sensitivity to CNS-active drugs. Always take a thorough medication history and consider potential drug interactions before administering any drug.