Question

A 25 yr old male experienced severe flushing, fall in blood pressure after intake of alcohol. The above described attack can be precipitated by the simultaneous intake of all the following drugs along with alcohol EXCEPT which?

• A. Cefamandole
• B. Metronidazole
• C. Dexamethasone
• D. Chlorpropamide

Hint:

This drug does not block aldehyde dehydrogenase, unlike the others.

Answer 1

The Correct Option is C

The case describes flushing and a fall in blood pressure with alcohol, which is the disulfiram-like reaction. We need to find which drug does NOT cause this.

1. Cefamandole: Carries a side chain that blocks the enzyme aldehyde dehydrogenase, letting acetaldehyde build up and trigger the reaction with alcohol.
2. Metronidazole: A classic cause of this reaction, blocking the same enzyme, which is why alcohol is always avoided during treatment with it.
3. Dexamethasone: A steroid drug that works on hormone receptors, with no effect on the enzyme that breaks down acetaldehyde. It does not cause this reaction.
4. Chlorpropamide: An old diabetes drug that can also block the enzyme in some people, causing flushing with alcohol.

Since three of the four drugs block the enzyme that clears acetaldehyde, and dexamethasone does not touch this pathway at all, dexamethasone is the one that will not cause the reaction.

Let's summarize:

• The disulfiram-like reaction comes from acetaldehyde build up when aldehyde dehydrogenase is blocked.
• Cefamandole, metronidazole, and chlorpropamide can all block this enzyme; dexamethasone cannot.

The correct answer is dexamethasone.