Understanding Pharmacology in EMS
Pharmacology is the study of how medications interact with the body. For EMS providers, pharmacological knowledge encompasses understanding which medications to give, when to give them, how to give them, and what effects (both desired and adverse) to expect. The NREMT tests pharmacology concepts at every certification level, and the complexity increases from EMT through paramedic. Even at the EMT level, you must understand the medications you administer, the medications your patients take, and how those medications affect your assessment and treatment.
Every medication has three names: a chemical name (describes the molecular structure, rarely used clinically), a generic name (the official name assigned by the United States Adopted Names Council, always lowercase), and a trade (brand) name (the manufacturer's proprietary name, always capitalized). For example, the chemical name is N-acetyl-para-aminophenol, the generic name is acetaminophen, and the trade name is Tylenol. Know both generic and trade names for all medications in your formulary.
Key Pharmacological Concepts
Pharmacokinetics: What the Body Does to the Drug
Pharmacokinetics has four phases: absorption (how the drug enters the bloodstream, affected by route of administration), distribution (how the drug travels through the body to reach target tissues), metabolism (how the body breaks down the drug, primarily in the liver), and excretion (how the body eliminates the drug, primarily through the kidneys). These phases determine onset of action, duration of effect, and dosing frequency.
Pharmacodynamics: What the Drug Does to the Body
Pharmacodynamics describes how drugs produce their effects. Most drugs work by binding to receptors on cell surfaces. An agonist binds to a receptor and activates it (albuterol activates beta-2 receptors, causing bronchodilation). An antagonist binds to a receptor and blocks it (naloxone blocks opioid receptors, reversing opioid effects). Understanding agonist-antagonist relationships helps predict drug effects, side effects, and interactions.
EMT-Level Medications
EMTs are authorized to administer or assist with a limited set of medications:
- Oral glucose: Indication: hypoglycemia in a conscious patient who can swallow. Dose: one tube (15 to 24 grams) placed between the cheek and gum.
- Aspirin: Indication: suspected acute coronary syndrome. Dose: 160 to 325 mg chewed. Contraindications: aspirin allergy, active GI bleeding, recent surgery.
- Epinephrine auto-injector: Indication: anaphylaxis. Dose: 0.3 mg IM (adult), 0.15 mg IM (pediatric). Administered in the lateral thigh.
- Naloxone: Indication: suspected opioid overdose with respiratory depression. Dose: 2 mg intranasal or per protocol.
- Nitroglycerin: Indication: chest pain of suspected cardiac origin (assist patient with their own prescribed nitroglycerin). Dose: 0.4 mg sublingual. Contraindications: systolic BP below 100, recent phosphodiesterase inhibitor use, right ventricular infarction.
Patient Medication Assessment
Beyond the medications you administer, you must be able to assess the implications of your patient's own medications. Beta-blockers (metoprolol, atenolol) prevent compensatory tachycardia in shock. Blood thinners (warfarin, apixaban) increase bleeding risk in trauma. Insulin and oral hypoglycemics cause hypoglycemia. ACE inhibitors can cause angioedema. Always bring the patient's medications to the hospital and note them on your patient care report.