Does antebuse work because of a placebo effect?

No. In a sense, the fear of an disulfiram-alcohol reaction is a deterrent, stopping people from drinking. That is what it is supposed to do. However, if you drink on antabuse, most people find that the violent nausea, vomiting, worst headache of your life, flushing, low blood pressure and even fainting is far from a placebo effect. There are better drugs to stop craving - Campral and naltrexone.
No. Antabuse (disulfiram) blocks acetaldehyde enzyme, which is needed for the body to get rid of alcohol. If a person drinks alcohol when the enzyme is blocked, acetaldehyde levels get high and cause nausea, vomiting, low blood pressure, and a miserable feeling. It is not a placebo effect.