Pharmacology in Nursing
Pharmacology is the study of drugs and how they interact with the body. Nurses need a solid understanding of pharmacological principles to administer medications safely, monitor for effects, and educate patients.
Pharmacokinetics
Pharmacokinetics describes what the body does to a drug — absorption, distribution, metabolism, and excretion (ADME):
- Absorption — How the drug enters the bloodstream (oral, IV, IM, topical, etc.)
- Distribution — How the drug travels through the body to reach its target
- Metabolism — How the drug is broken down (mainly in the liver)
- Excretion — How the drug leaves the body (mainly via kidneys in urine)
Pharmacodynamics
Pharmacodynamics describes what the drug does to the body — how it produces its effects. Drugs work by binding to receptors, blocking enzymes, or affecting ion channels. Key concepts include:
- Agonist — A drug that activates a receptor (e.g. morphine activating opioid receptors)
- Antagonist — A drug that blocks a receptor (e.g. naloxone blocking opioid receptors)
- Potency — The amount of drug needed to produce an effect
- Efficacy — The maximum effect a drug can produce
Drug Calculations
Nurses must be able to calculate drug doses accurately. Key formulas:
- Dosage — (Desired dose / Stock strength) × Volume or quantity
- IV infusion rate (ml/hr) — Total volume (ml) / Time (hours)
- Drip rate (drops/min) — (Volume (ml) × Drop factor) / Time (minutes)
- Body weight dose — Patient weight (kg) × Dose per kg
Drug Classifications
- Analgesics — Pain relief (paracetamol, NSAIDs, opioids)
- Antibiotics — Treat bacterial infections (penicillins, cephalosporins, macrolides)
- Antihypertensives — Lower blood pressure (ACE inhibitors, beta-blockers, diuretics)
- Anticoagulants — Prevent blood clots (warfarin, heparin, DOACs)
- Antidepressants — Treat depression (SSRIs, SNRIs, tricyclics)
- Antipsychotics — Manage psychosis (olanzapine, risperidone, haloperidol)
- Insulin — Manage diabetes (short-acting, long-acting, mixed)
Adverse Effects
All medications can cause adverse effects. Common ones include: nausea, vomiting, diarrhoea, constipation, rash, dizziness, and headache. Serious adverse effects include anaphylaxis, QT prolongation, and Stevens-Johnson syndrome. Report suspected adverse reactions to the MHRA via the Yellow Card Scheme.
Drug Interactions
Drug interactions occur when one drug affects the action of another. Examples include: warfarin and antibiotics (increased bleeding risk), ACE inhibitors and potassium supplements (hyperkalaemia), and opioids and benzodiazepines (respiratory depression).