IM22.4 | Drug Overdose — Summary & Reflection

KEY TAKEAWAYS

Drug overdose — five agents and their management:

• Paracetamol: silent hepatotoxicity; four phases (0-24h asymptomatic → 24-72h transaminase rise → 72-96h peak failure → recovery); mechanism = NAPQI glutathione depletion; antidote = NAC (most effective within 8 hours; start if 4-hour level above Rumack-Matthew treatment line); King's College Criteria for liver transplant referral; enzyme-inducing drugs and malnutrition lower the toxic threshold

• Benzodiazepine: GABA-A enhancement → sedation, respiratory depression, near-normal pupils; antidote = flumazenil (caution: BZD dependence, TCA co-ingestion); BZDs rarely fatal alone; danger in combination with alcohol/opioids

• Tricyclic antidepressant (TCA): triple toxicity — Na channel blockade (QRS widening, arrhythmia), anticholinergic (tachycardia, dry, mydriasis), alpha-1 block (hypotension); ECG: QRS >100 ms + R in aVR >3 mm; antidote = IV sodium bicarbonate (1–2 mEq/kg); AVOID flumazenil and physostigmine

• Opioid: mu-receptor → miosis + respiratory depression + coma; antidote = naloxone (0.4–2 mg IV, repeat; infusion for long-acting opioids); titrate to ventilation, not full reversal

• Salicylate: respiratory alkalosis + high anion gap metabolic acidosis; tinnitus, hyperthermia, agitation; management = urinary alkalinisation (target urine pH 7.5–8.5) + haemodialysis if level >100 mg/dL, AKI, acidosis pH <7.2, or CNS dysfunction

REFLECT

The 19-year-old in the opening hook — brought in asymptomatic at 2 am, wanting to leave, presenting staff with pressure to discharge — encapsulates the most dangerous scenario in drug overdose: the misleadingly well patient with time-dependent toxicity brewing beneath a normal exterior. Reflect on what systems you would put in place, as the treating doctor, to ensure that every paracetamol overdose patient gets a 4-hour level regardless of how well they appear. How does the emergency department culture around deliberate self-harm affect this — is the patient who appears well treated with the same urgency as the patient who appears critically ill? And consider the psychiatric dimension: this young woman will need more than a liver function test. What is your responsibility to her mental health in this encounter, and how does the medical assessment interact with the psychiatric referral that she also needs? Drug overdose sits at the intersection of medical emergency and psychiatric crisis — managing both dimensions simultaneously is the clinical skill the NMC expects of you.