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

Step 1: Name the reaction being described.
Flushing, palpitations, and a drop in blood pressure after drinking alcohol, while on certain drugs, describes a disulfiram-like reaction.

Step 2: Recall the mechanism.
Alcohol is normally broken down in two steps, first to acetaldehyde by alcohol dehydrogenase, then acetaldehyde is broken down further by aldehyde dehydrogenase. Certain drugs block this second enzyme, so acetaldehyde builds up in the blood. This build up causes the flushing, headache, nausea, and fall in blood pressure seen in a disulfiram-like reaction.

Step 3: Check each drug against this mechanism.
Cefamandole is a cephalosporin that carries a side chain (the MTT or NMTT group) known to block aldehyde dehydrogenase, so it can trigger this reaction with alcohol.
Metronidazole is well known to block aldehyde dehydrogenase and produce this same reaction, so patients are always told to avoid alcohol while taking it.
Chlorpropamide, an older sulfonylurea used for diabetes, also blocks this enzyme in some patients and can cause facial flushing with alcohol.
Dexamethasone is a corticosteroid. It works through steroid hormone receptors and has no action on aldehyde dehydrogenase, so it does not cause this reaction with alcohol.

Step 4: Conclude.
Since cefamandole, metronidazole, and chlorpropamide can all precipitate the reaction but dexamethasone cannot, dexamethasone is the exception.

Final Answer:
\[ \boxed{\text{Dexamethasone}} \]