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Disulfiram reaction matters because disulfiram is a deterrent drug, one designed to make drinking alcohol unpleasant on purpose, rather than a drug that reduces craving directly. It works by inhibiting aldehyde dehydrogenase, a liver enzyme that normally breaks down acetaldehyde, a toxic by-product of alcohol metabolism. Blocking this enzyme lets acetaldehyde build up if the patient drinks, producing an unpleasant reaction that discourages further drinking. For example, imagine a patient on disulfiram who has a single glass of wine at a party: within minutes they develop flushing, a pounding headache and nausea, an unpleasant reminder of why they are avoiding alcohol. In practice, the threat of this reaction, not a direct effect on craving, is what supports abstinence.

Disulfiram inhibits aldehyde dehydrogenase, so any alcohol consumed is only broken down as far as acetaldehyde, which then accumulates in the blood. The resulting reaction includes flushing, throbbing headache, nausea and vomiting, palpitations, and hypotension (low blood pressure), and can be severe enough to cause collapse. Patients must avoid all sources of alcohol, not just drinks, since mouthwash, perfume, some cough syrups and even alcohol-based cooking sauces can trigger it. For example, imagine a patient on disulfiram who uses an alcohol-based mouthwash without realising: they can still develop flushing and palpitations from that small exposure. In practice, this means counselling every patient starting disulfiram to check the alcohol content of toiletries and foods, not only their drinks cabinet.

• A man stops taking disulfiram and asks how long he must avoid alcohol afterwards. Which period of continued caution should he be advised to observe?
• A man on high-dose disulfiram develops paranoid delusionsA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more → without drinking alcohol. Inhibition of which additional enzyme best explains this psychiatric complication?
• A team is deciding how best to prescribe disulfiram for a man with repeated relapses. Which arrangement is most strongly associated with better outcomes?
• A woman with a history of a psychotic illness asks about disulfiram for alcohol relapse prevention. Why does this history warrant particular caution?

• Disulfiram reaction, acetaldehyde accumulation from aldehyde dehydrogenase inhibition, unlike naltrexone, which reduces the rewarding effect of alcohol without causing a physical reaction.
• Acamprosate, reduces craving via glutamate-GABAThe brain's main calming (inhibitory) chemical messenger, boosted by benzodiazepines and alcohol.Read more → effects, whereas disulfiram works purely as a deterrent through an unpleasant physical reaction.
• Serotonin syndrome, caused by excess serotonergicRelating to serotonin, a brain chemical involved in mood.Read more → activity with clonusRhythmic, involuntary muscle contractions, often tested at the ankle.Read more → and hyperreflexiaOveractive or overresponsive reflexes.Read more →, rather than the acetaldehyde-driven flushing and hypotension of a disulfiram reaction.
• Carcinoid syndrome flushing, caused by serotonin and other vasoactive substances from a neuroendocrine tumour, unlike disulfiram flushing which requires recent alcohol exposure.

• Blocking that enzyme causes the flushing reaction, not psychosis without alcohol.
• That enzyme is not meaningfully inhibited by this drug.
• Enzyme inhibitionA drug reducing the activity of a liver enzyme, which slows the breakdown and raises the level of other drugs sharing that enzyme.Read more → persists far longer than a single day after stopping.
• This underestimates how long the enzyme blockade lasts.
• A reaction remains possible beyond this point after the last dose.

• Identify the drug, receptor, enzyme or pharmacokinetic change named in the stem.
• Translate it into the immediate mechanism before looking at the options.
• Use timing and the adverse-effect pattern to separate the nearest alternatives.
• Check whether the question asks for mechanism, clinical consequence, monitoring or management.