Final answer:
The most serious complication for a patient who ingests alcohol (ETOH) while on disulfiram is a severe and potentially life-threatening reaction known as disulfiram-ethanol reaction (DER).
Step-by-step explanation:
The most serious complication for a patient who ingests alcohol (ETOH) while on disulfiram is a severe and potentially life-threatening reaction known as disulfiram-ethanol reaction (DER). DER occurs due to the interaction between disulfiram and alcohol, which leads to a buildup of acetaldehyde in the body. This can result in symptoms such as flushing, headache, nausea, vomiting, sweating, dizziness, and hypotension. In severe cases, DER can cause respiratory distress, cardiovascular collapse, and even death.