💊 Naltrexone and acamprosate: medications for alcohol dependence in Australia ✨

Australia has two PBS-subsidised medications specifically for alcohol dependence — naltrexone and acamprosate — plus a third (disulfiram) used in selected cases. They are under-prescribed relative to the evidence: probably fewer than 10% of Australians who would benefit from one are receiving one. This is what they actually do, who they suit, and how to access them.

Why pharmacotherapy for alcohol matters

Alcohol use disorder (AUD) is the most common substance use disorder in Australia by a wide margin. The evidence base for psychological treatment is good; the evidence base for pharmacotherapy is also good and substantially older than most people realise — naltrexone has been in use for AUD since the 1990s, acamprosate since shortly after.

Yet pharmacotherapy is offered to a small minority of Australians presenting with AUD. The reasons are partly clinical inertia (GPs are not always trained in their use), partly the ongoing tendency to view alcohol problems as primarily moral or behavioural, and partly the sheer scale of AUD compared to public AOD service capacity. The result is that meaningful, evidence-based, PBS-subsidised treatment is sitting on the shelf for many people.

Naltrexone in plain English

Naltrexone is an opioid receptor antagonist — meaning it blocks the brain's opioid receptors. This sounds odd in an alcohol context, but the mechanism is well understood: alcohol consumption triggers release of endogenous opioids (endorphins) in the brain's reward circuit, and that opioid signal is a meaningful part of the pleasurable, reinforcing experience of drinking. Naltrexone blocks the opioid receptors, so the reward signal does not land. Over time, drinking becomes less reinforcing.

How it is taken. One 50mg tablet daily, taken at any time. Some prescribers use it on a "targeted" basis — taken an hour before an anticipated drinking situation rather than every day — though daily use has stronger evidence.

What it does and does not do. It does not make you sick if you drink (that is disulfiram). It does not eliminate cravings entirely. It does, on average across the literature, reduce heavy-drinking days, reduce the number of drinks consumed when drinking does occur, and roughly double the chance of remaining abstinent over the treatment period.

Who it suits. People whose pattern is binge-and-recover — heavy episodes followed by attempts at abstinence. People for whom craving is the main driver. People who can tolerate the medication well (most can; common side effects are nausea, headache, and fatigue, usually mild and time-limited).

Important precautions. Naltrexone cannot be taken alongside opioid pain medications — it will block the analgesic effect, and in someone opioid-dependent it can precipitate withdrawal. People who may need opioids for surgery or significant pain need to plan around this. Naltrexone is also processed by the liver and is generally avoided in significant liver disease. Long-acting injectable naltrexone (Vivitrol) is available in Australia privately, though less commonly used than the daily tablet.

Acamprosate in plain English

Acamprosate works on a different system. After sustained heavy drinking, the brain's glutamate (excitatory) and GABA (inhibitory) systems become dysregulated. When alcohol is removed, the excitatory glutamate system is left over-active, producing the prolonged anxiety, sleeplessness, irritability, and craving that typify post-acute withdrawal — sometimes for months. Acamprosate dampens this excitatory excess and lets the brain rebalance.

How it is taken. Two 333mg tablets three times daily — six tablets total. The dosing is the main practical drawback; it is harder to remember than once-a-day medications and works best when integrated into routine (with each meal, for instance).

What it does and does not do. Reduces post-acute withdrawal symptoms, supports abstinence, and reduces relapse rates. It is most effective when started after the person has stopped drinking — ideally during or shortly after acute detox — and continued for at least six months. Less useful in people who are still drinking heavily.

Who it suits. People who have achieved or are achieving abstinence and want pharmacological support to maintain it. People for whom post-acute withdrawal is prolonged or severe. People whose primary goal is sustained abstinence rather than reduced drinking.

Precautions. Acamprosate is processed by the kidneys, so dose reduction or avoidance is needed in significant kidney disease. Side effects are typically mild — diarrhoea is the most common. Unlike naltrexone, it can be safely combined with opioid pain medication.

Disulfiram (Antabuse) — the older option

Disulfiram is the medication that does make you sick if you drink. It blocks the enzyme that breaks down acetaldehyde, an alcohol metabolite, so any drinking on top of disulfiram produces a fast, unpleasant reaction — flushing, nausea, palpitations. The evidence is mixed, but it can be useful for highly motivated people in supervised contexts (where someone observes the daily dose) — the predictable consequence helps interrupt the impulsive drinking that precedes many relapses. It is rarely a first-line choice in current Australian practice and is generally not used without careful screening for cardiac and liver health.

Choosing between naltrexone and acamprosate

Both medications are PBS-listed for alcohol dependence and both are first-line options in Australia. The choice often comes down to:

• Goal. Acamprosate is most clearly a maintenance-of-abstinence medication. Naltrexone works for both abstinence and reduced drinking.
• Pain medication needs. If the person is likely to need opioids — chronic pain, upcoming surgery — acamprosate is the safer choice.
• Liver vs kidney function. Naltrexone is processed by the liver; acamprosate by the kidneys. Whichever organ is in better shape suggests the medication.
• Pill burden. One tablet a day (naltrexone) versus six tablets a day (acamprosate). For some people, this alone settles it.
• Combined treatment. The two can be used together. The COMBINE trial showed naltrexone plus medical management was as effective as either combined with structured psychotherapy. Some Australian prescribers use both naltrexone and acamprosate concurrently in selected cases.

What the trial evidence actually says

Both medications have effect sizes that are statistically significant and clinically meaningful, but moderate — not transformative. Across the Cochrane reviews and the meta-analyses, naltrexone roughly halves the chance of returning to heavy drinking and reduces drinking days. Acamprosate roughly halves the chance of returning to any drinking at all, in those who have achieved abstinence at the start of treatment. Neither makes alcohol dependence go away. Both work better when combined with psychological treatment and lifestyle change. Both are dramatically better than nothing, which is what a large fraction of Australians with AUD currently receive.

How to access these medications in Australia

Both naltrexone and acamprosate are PBS-listed for alcohol dependence and can be prescribed by any Australian GP. No specialist consultation is required. The PBS-subsidised cost is the standard concession or general co-payment per script. A typical workflow:

1. GP appointment, ideally one with some addiction experience. Discussion of the goal (abstinence vs reduced drinking), drinking history, liver and kidney function, current medications.
2. Baseline blood tests — liver function, full blood count, and either renal function (for acamprosate) or specific liver markers (for naltrexone).
3. Prescription, usually with a follow-up review in 2-4 weeks.
4. Concurrent referral, where the person is willing, to psychological treatment — Medicare Better Access Mental Health Care Plan, NewAccess for milder cases, or a public AOD service for more complex situations.

Where a GP is not confident prescribing, the next-best step is a private addiction medicine specialist or a public AOD service. State alcohol and drug lines can navigate the local landscape. Both medications are also routinely prescribed during inpatient detox in public and private rehabs, and continued as discharge medication.

The under-treatment problem

The single most striking fact about these medications in Australia is how rarely they are offered. The most common reasons people who would benefit from them do not receive them are: their GP did not raise the option, they did not know the medications existed, they assumed pharmacotherapy was only for opioid dependence, or they tried a brief course, did not feel an immediate effect, and stopped. Patients who go in already knowing the medications exist and asking by name typically have much better access. That is the practical implication of this guide — if you read this and think one of these medications might fit your situation, walk into a GP appointment and say so.