Medical Emergencies · patient case question
What is the mechanism of action of lisinopril?
Patient case: Blood pressure, potassium and a pounding headache
demo: 63-year-old male
chief: Presents for extraction of a hopeless mandibular molar.
history: Hypertension for fifteen years. He tells you he ran out of his tablets ten days ago. His father died of a subarachnoid haemorrhage.
meds: Lisinopril 20 mg daily. Triamterene with hydrochlorothiazide, one tablet each morning.
findings: Blood pressure on arrival is 204/122 mmHg in both arms, repeated after five minutes of rest. He describes a severe occipital headache that began this morning and some blurring of vision.
Show answer and explanation
Correct answer: D. Inhibition of angiotensin converting enzyme
- A. That describes the sartans such as losartan and valsartan. They block the receptor rather than the enzyme, which is why they do not cause the bradykinin cough.
- B. Beta-1 blockade describes metoprolol and atenolol, which lower heart rate and cardiac output.
- C. Calcium channel blockade describes amlodipine and nifedipine. Nifedipine is the one to remember for drug-influenced gingival enlargement.
- D. Correct. Lisinopril blocks the enzyme that converts angiotensin I to angiotensin II, lowering vasoconstriction and aldosterone release. The same enzyme degrades bradykinin, so bradykinin accumulates, which explains the dry cough and the risk of angioedema.
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