Pharmacology · patient case question
Which of his medications most increases the cardiovascular risk of a local anaesthetic containing epinephrine?
Patient case: A long medication list before an extraction
Patient: Male, 58 years old
Chief Complaint: Presents for extraction of a non-restorable maxillary premolar.
Background: Hypertension and migraine. Longstanding depression.
Medications: Propranolol 80 mg twice daily · imipramine 75 mg nightly · sumatriptan as required · acetaminophen as required
Vital Signs: BP 138/86 mmHg · HR 58 bpm · RR 16
Findings: Tooth #5 is non-restorable. Following an infiltration in the maxillary buccal vestibule he is temporarily unable to raise the upper lip on that side, which alarms him.
Show answer and explanation
Correct answer: C. Imipramine
- A. There is a clear interaction here, and in fact two — the tricyclic with epinephrine, and the non-selective beta blocker with both epinephrine and lidocaine.
- B. Acetaminophen has no adrenergic activity and no interaction with epinephrine.
- C. CORRECT. IMIPRAMINE is a TRICYCLIC ANTIDEPRESSANT. Tricyclics block the reuptake of noradrenaline at the adrenergic nerve terminal, so an injected vasoconstrictor is not cleared from the synapse normally and its pressor effect is markedly EXAGGERATED — producing hypertension and dysrhythmias. Epinephrine is not absolutely contraindicated, but the dose must be limited (a commonly cited ceiling is about 0.04 mg, roughly two cartridges of 1:100,000), aspiration is essential, and LEVONORDEFRIN and NORADRENALINE must be AVOIDED ENTIRELY, since the interaction with those agents is far more severe. Tricyclics also cause pronounced xerostomia, orthostatic hypotension and a lowered seizure threshold.
- D. Sumatriptan is a selective SEROTONIN (5-HT1B/1D) RECEPTOR AGONIST used for acute migraine. It is not an antidepressant and not an SSRI. It matters medically — it causes coronary vasoconstriction and is contraindicated in ischaemic heart disease and uncontrolled hypertension — but it is not the drug driving the interaction with the vasoconstrictor.
Note: ⚠️ The recall author described sumatriptan as ‘an SSRI I haven't heard of’. It is a serotonin receptor AGONIST, not a reuptake inhibitor. The drug responsible for the exaggerated cardiovascular response in this list is the TRICYCLIC. Keep the classes straight: TCAs exaggerate the epinephrine response; non-selective beta blockers give unopposed alpha stimulation; SSRIs and MAOIs, contrary to older teaching, do NOT require epinephrine restriction in dental doses.