Drug Interactions in Dentistry

Alcohol (disulfiram-like reaction). Metronidazole + alcohol causes a disulfiram-like reaction.

Tricyclic antidepressants. TCAs potentiate the pressor effect of epinephrine.

Bleeding. Both affect haemostasis, increasing bleeding risk.

⭐ High-Yield Facts for Exam

Warfarin + NSAIDs/aspirin — increased bleeding risk (and NSAIDs displace warfarin).
Warfarin + metronidazole/erythromycin/fluconazole — increased anticoagulant effect (raised INR).
Epinephrine + tricyclic antidepressants (TCAs) / non-selective β-blockers — risk of hypertensive response.
Metronidazole + alcohol — disulfiram-like reaction.
Erythromycin/azole inhibition of CYP3A4 raises levels of many drugs.

Review the medical/drug history before prescribing or using vasoconstrictors.

Warfarin + NSAID = bleeding; epinephrine + TCA = hypertensive risk; metronidazole + alcohol = disulfiram reaction.

Q1. Metronidazole interacts dangerously with:

A. Alcohol (disulfiram-like reaction)

B. Vitamin C

C. Antacids

D. Iron

Show Answer

✅ Answer: A

Metronidazole + alcohol causes a disulfiram-like reaction.

Q2. Epinephrine should be used cautiously with:

A. Paracetamol

B. Tricyclic antidepressants

C. Amoxicillin

D. Antacids

Show Answer

✅ Answer: B

TCAs potentiate the pressor effect of epinephrine.

Q3. Combining warfarin with NSAIDs increases the risk of:

A. Sedation

B. Bleeding

C. Constipation

D. Hyperglycemia

Show Answer

✅ Answer: B

Both affect haemostasis, increasing bleeding risk.

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