12.5 Toxicology & Poisoning Management

12.5 Toxicology & Poisoning Management

Quick Answer: APC names toxicology as an exam content area. The pharmacist-level skills are knowing that the Poisons Information Centre is 13 11 26, available 24 hours a day from anywhere in Australia; recognising when to call 000 instead; understanding that paracetamol toxicity is silent early; knowing take-home naloxone; and preventing poisoning through packaging, storage and disposal advice.

Poisoning presents to pharmacies constantly — a toddler who found a handbag, an older person who took a double dose, a distressed adult who has taken tablets, a person who mixed two cold-and-flu products. Standard 3.2 covers your acute response and Standard 3.3 covers recognising toxicity in ongoing therapy.

The two numbers you must know

The Poisons Information Centre advises the public and provides toxicology advice to health professionals. Calling it is not an admission of ignorance; it is the correct professional action, and it is the answer that scores marks in an exam scenario about an uncertain ingestion.

Structured risk assessment

Before you advise anything, gather:

1. Agent — the exact product, active ingredients and strength; get the pack if possible
2. Dose — how much, using worst-case assumptions when the amount is uncertain
3. Time — when the exposure occurred, and whether it was a single event or repeated
4. Patient — age, weight, pregnancy, comorbidities, renal and hepatic function, other medicines
5. Intent — accidental, therapeutic error, or deliberate self-harm

Any deliberate self-poisoning requires medical assessment regardless of the dose taken, because the psychosocial risk is the reason for referral, not just the pharmacology. Respond without judgement, keep the person safe, and arrange assessment.

What not to do

• Do not induce vomiting. Ipecac is obsolete and can cause harm.
• Do not give activated charcoal on your own initiative. It is a clinical decision with a narrow time window and real aspiration risk, made in a healthcare setting.
• Do not routinely give milk, water or food without advice — it can be wrong for corrosives and some agents.
• Do not reassure on the basis of how well the person looks. Several important poisonings are asymptomatic for hours.

Paracetamol — the poisoning pharmacists meet most

Paracetamol is the medicine most often responsible for poisoning hospital admissions in Australia. Key teaching:

• Early symptoms are absent or trivial — nausea at most. A patient who "feels fine" four hours after a large ingestion may still be heading for liver failure.
• Assessment uses a timed plasma paracetamol concentration, typically from four hours after an acute ingestion, interpreted against a treatment nomogram. Staggered or repeated supratherapeutic ingestion cannot be assessed by the nomogram and needs direct clinical assessment.
• The antidote is acetylcysteine (N-acetylcysteine), most effective when started early. Never delay referral to "see how they go".
• Risk is increased by chronic alcohol use, malnutrition, low body weight, and enzyme-inducing medicines.
• Modified-release paracetamol overdose behaves differently from immediate-release and requires specialist toxicology advice.

The 2025 pack-size changes are exam-relevant

From 1 February 2025, Australia tightened paracetamol availability to reduce overdose harm:

• Non-pharmacy retailers such as supermarkets and convenience stores may sell packs of no more than 16 tablets or capsules
• Pharmacy Medicine (Schedule 2) packs are limited to 50 tablets or capsules
• Larger packs, up to 100, became Pharmacist Only (Schedule 3) and require pharmacist involvement
• Blister packaging is required for tablets and capsules

This is a live example of scheduling changing to manage a toxicological risk, and it links directly to the Schedule 2 and 3 material in Chapter 2.

Opioid overdose and take-home naloxone

Recognise the triad: reduced consciousness, slow or absent breathing, and pinpoint pupils. Call 000, support the airway, and give naloxone if available.

Australia's Take Home Naloxone program supplies naloxone free and without a prescription through participating pharmacies to anyone who may experience or witness an opioid overdose. Offer it proactively when supplying higher-dose opioids, when a person uses opioids with benzodiazepines or alcohol, after a period of abstinence when tolerance has fallen, and to family members. Counsel that naloxone is shorter acting than most opioids, so the person must still go to hospital even if they wake up.

Toxidromes worth recognising

Narrow therapeutic index medicines

Some medicines poison patients at doses close to their therapeutic range, which is why they carry monitoring requirements: lithium, digoxin, warfarin, phenytoin, theophylline, methotrexate and aminoglycosides. Dehydration, an added interacting medicine or a decline in renal function can convert a stable regimen into a toxic one without any change in the prescribed dose. Recognising that pathway is a Standard 3.3 skill.

Poisoning prevention — the pharmacist's daily contribution

• Child-resistant closures and advice to keep medicines up high, locked and out of sight, including handbags and bedside tables
• Oral dosing devices supplied and demonstrated — never a kitchen teaspoon
• Counselling on maximum daily doses and on hidden duplicate ingredients in combination cold-and-flu products, which is a leading cause of accidental paracetamol excess
• Encouraging return of unwanted and expired medicines to a community pharmacy through the national Return Unwanted Medicines (RUM) project rather than bins or the toilet
• Reviewing dose administration aids for people at risk of confusion or double-dosing

Exam mindset

Toxicology stems reward decisive, correct escalation. Know 13 11 26 and when 000 comes first, never induce vomiting, never reassure on appearance after a paracetamol ingestion, offer take-home naloxone before you are asked, and remember that deliberate ingestion always needs assessment regardless of dose.