5.4 Alcohol & Drug Interactions

Why Drug Interactions Belong in the LCQ

Section 5 of the Sale and Supply of Alcohol Act 2012 defines intoxication as being observably affected by alcohol, other drugs, or other substances (or a combination). The duty manager's lawful test — two or more of appearance, behaviour, coordination and speech — applies equally to a patron affected by alcohol plus medication, alcohol plus illegal drugs, or drugs alone. A server who only looks for 'drunk' signs will miss a drug-affected patron who is a real risk to themselves and others.

Additive and Synergistic (Potentiation) Effects

The most dangerous class of interaction is when alcohol is combined with other central nervous system depressants. The effects are often additive and can be synergistic (more-than-additive) — meaning the combined sedation is greater than the sum of each drug alone.

Common CNS depressants that interact with alcohol

A patron on a prescribed benzodiazepine may show pronounced slurred speech and unsteadiness after only one or two standard drinks — well below their 'usual' tolerance. The duty manager does not need to know the prescription; the visible signs are enough to intervene.

Disulfiram-Type Reactions

Disulfiram (Antabuse) is a medication prescribed to support alcohol abstinence. It inhibits aldehyde dehydrogenase, so acetaldehyde accumulates when alcohol is consumed. The result is nausea, vomiting, flushing, headache, palpitations and hypotension within minutes of drinking. A patron on disulfiram who consumes alcohol can become acutely unwell on the premises.

Several other drugs produce a similar (disulfiram-like) reaction with alcohol, including some antibiotics (metronidazole, tinidazole) and some antifungals. A patron who suddenly becomes flushed, nauseated and unwell shortly after one drink may be experiencing this reaction rather than ordinary intoxication, and may need medical attention.

Stimulants Combined with Alcohol

Stimulants (cocaine, methamphetamine, MDMA, prescription stimulants) interact with alcohol in a different and dangerous way: they can mask the visible signs of intoxication. The stimulant counteracts the sedation, so the patron appears less affected than their BAC would suggest. Risks include:

• The patron consumes more alcohol than they would otherwise, then experiences a sudden crash when the stimulant wears off, leaving them deeply impaired.
• The patron undertakes risky behaviour (driving, fighting, sexual risk) believing they are sober.
• Cocaine + alcohol forms cocaethylene in the liver, a compound that is cardiotoxic — more toxic to the heart than cocaine alone and longer-lasting. This is a documented cause of sudden cardiac events in younger users.

A duty-manager cue: a patron who is drinking steadily but appears 'too composed' for the amount consumed, then suddenly deteriorates, may be coming down from a stimulant.

Paracetamol and Chronic Alcohol

Paracetamol (acetaminophen) is broadly safe at normal doses, but chronic heavy alcohol use induces liver enzymes that turn a paracetamol dose into toxic by-products, raising the risk of liver damage. This is a long-term health risk rather than a venue emergency, but it is a recognised interaction the exam may test.

Illegal Drugs in Licensed Premises

The duty manager must also be alert to illegal drugs being consumed on or near the premises, because they change the patron's presentation and the venue's safety profile:

• Cannabis — additive impairment with alcohol: sedation, impaired coordination, slower reaction, poorer judgement. Often combined with alcohol by patrons who understate their level of impairment.
• Methamphetamine — agitation, erratic and aggressive behaviour, hyperthermia, dehydration. A patron who is jittery, sweating heavily, aggressive or paranoid needs immediate intervention; the risk to staff and other patrons is high.
• MDMA (ecstasy) — in a hot, crowded venue, MDMA can cause dehydration and hyperthermia (heatstroke), which can be life-threatening. Patrons may be over-hydrating to compensate, which carries its own risk (hyponatraemia). Visible signs include jaw clenching, sweating, confusion, and overheating despite the ambient temperature.
• GHB and ketamine — heavy sedation, loss of motor control, vulnerability. GHB in particular is associated with drink spiking and with patrons becoming rapidly incapacitated. A patron who was well and suddenly appears deeply sedated, confused, or unable to stand may have been spiked.

Drink-Spiking Vigilance

Duty managers and servers should watch for the warning signs of drink spiking:

• a patron who suddenly appears far more intoxicated than their drink count would explain,
• a patron who becomes dizzy, confused or loses consciousness quickly,
• a patron who reports their drink tasting odd or appearing cloudy,
• an unknown person buying or delivering a drink to a patron without their knowledge.

The response is to keep the patron safe (do not leave them alone, do not let them leave with a stranger), offer non-alcoholic drinks and water, arrange safe transport, and call medical assistance or police if the patron deteriorates. Record the incident in the incident book with times, descriptions and actions taken.

Duty-Manager Implications and the s5 Test

The legal and operational consequences for the duty manager are:

1. A patron on medication may be impaired well below their usual drink count. The duty manager does not ask what medication they are on; the duty manager observes the SCAB signs and intervenes.
2. Drug-affected patrons are harder to assess and higher risk. Stimulants can mask signs; sedatives can deepen impairment unpredictably; illegal drugs can produce aggression or medical emergencies.
3. The s5 intoxication definition covers alcohol, other drugs, and other substances. You may refuse service to a patron observably affected by drugs, by alcohol, or by a combination, on the same SCAB test.
4. Service to an intoxicated person is an offence under s248 regardless of whether the intoxication is from alcohol alone or alcohol plus drugs. The penalty is up to $10,000 and/or a seven-day licence suspension.
5. Record-keeping matters. Any incident involving suspected drug use, drink spiking, or a patron becoming unwell should be recorded in the incident book with time, patron description, staff actions, and any police or medical involvement. Good records protect the licence and the duty manager at any DLC or ARLA hearing.

Practical Scenario

A patron who has been drinking wine steadily for two hours suddenly becomes drowsy, slumps at the bar, and is difficult to rouse — far more affected than the drink count would predict. The duty manager's working assumption should be a possible drug interaction or drink spiking, not 'just tired'. Stop service immediately, move the patron to a safe place with a staff member, offer water, do not let them leave alone or with a stranger, and call for medical help if they do not recover quickly. Record everything.