Disulfiram (Antabuse) is an oral medication used to facilitate abstinence from alcohol in patients who remain in a state of enforced sobriety.  It works to motivate patients to avoid alcohol due to its effect on alcohol metabolism, which can cause unpleasant symptoms if alcohol is ingested.  These unpleasant symptoms include, but are not limited to, causing facial flushing, tachycardia, nausea, vomiting, hepatotoxicity, and extrapyramidal symptoms. 

The development of this adverse event occurs upon the ingestion of alcohol (ethanol), which gets metabolized to acetaldehyde in the cytosol of hepatocytes (i.e., liver cells) via the enzyme hepatic alcohol dehydrogenase.(1) This newly formed acetaldehyde then gets converted to acetate by the enzyme aldehyde dehydrogenase.  Disulfiram exerts its pharmacologic effect by irreversibly inhibiting the enzyme aldehyde dehydrogenase, thereby resulting in an accumulation of acetaldehyde.(2)  The accumulation of acetaldehyde is influenced by the amount of alcohol ingested and results in the unpleasant development of the symptoms associated with a disulfiram like reaction.
  

            
  

References:

1. Lieberman M, Marks, A.  Metabolism of ethanol. In: Mark's Basic Medical Biochemistry A Clinical Approach.  Lieberman M, Marks A Eds. 3^rd Ed.  Wolters Kluver/Lippencott Williams & Wilkins.  Philadelphia, PA. 2009; 464-477.
2. Peachey JE, Sellers EM.  The disulfiram and calcium carbimide acetaldehyde-mediated ethanol reactions.  Pharmacol Ther 1981;15:89-97.

Disulfiram, Antabuse, Alcohol, Ethanol, Disulfiram Alcohol Interaction