Which drug classes pose a substantial risk of side effects in combination with alcohol and require a warning on the prescription label?

• A. Disulfiram (ex chlorpropamide, metronidazole)
• B. MAO inhibitors
• C. Nitrates
• D. All of the above

Answer: (D)

Some drugs have interactions with alcohol that can cause serious or disconcerting effects, so labeling them with an alcohol-warning helps protect patients. One category includes drugs that can produce a disulfiram-like reaction when alcohol is consumed. This isn't limited to disulfiram itself; chlorpropamide, a first-generation sulfonylurea, and metronidazole are classic examples. When alcohol is taken with these agents, acetaldehyde accumulates and leads to flushing, rapid heartbeat, nausea, vomiting, headache, and sometimes hypotension. The prescription label warns patients to avoid alcohol during therapy.

Another important interaction involves MAO inhibitors. Alcohol can contribute to dangerous blood pressure changes when combined with these drugs, and labels typically caution patients to avoid alcohol (and certain other foods or substances) to prevent hypertensive crises or other severe reactions.

Nitrates also pose a risk when alcohol is used concomitantly. Alcohol can augment the vasodilatory effects of nitrates, increasing the chance of dizziness, lightheadedness, or fainting due to hypotension. The warning helps patients avoid these outcomes.

Because each of these drug classes has a clinically meaningful risk with alcohol and requires a warning on the prescription label, the correct choice is all of the above.