Which drug interferes with the breakdown of alcohol and causes unpleasant reactions if alcohol is consumed?

Disulfiram is a medication designed to support the treatment of alcohol dependency by creating an aversive reaction when alcohol is consumed. It works by inhibiting the enzyme aldehyde dehydrogenase, which is responsible for metabolizing acetaldehyde, a toxic byproduct of alcohol metabolism. When alcohol is ingested while taking disulfiram, acetaldehyde accumulates in the body, leading to unpleasant symptoms such as flushing, palpitations, nausea, and vomiting. This reaction serves as a deterrent to drinking, promoting abstinence in individuals recovering from alcohol use disorder.

The other options, while relevant in the context of treating alcohol use disorder, do not operate in the same way. Naltrexone is an opioid antagonist that helps reduce cravings and the rewarding effects of alcohol but does not cause adverse reactions when alcohol is consumed. Acamprosate primarily helps to stabilize the chemical balance in the brain following alcohol cessation and does not produce negative effects with alcohol intake. Varenicline is primarily indicated for smoking cessation and affects nicotine receptors, showing no interaction with alcohol metabolism.