Pharmacology · patient case question
How does nitroglycerin relieve her angina?
Patient case: Chest pain during treatment in a patient with angina
Patient: Female, 65 years old
Chief Complaint: Presenting for a scheduled restoration.
Background: Stable angina for six years, hypertension, hyperlipidaemia. Medications: sublingual nitroglycerin as required, atorvastatin, losartan, aspirin 81 mg. She has brought her own nitroglycerin spray and it is in her handbag.
Vital Signs: On seating BP 142/84 mmHg · HR 78 bpm. During treatment she reports MILD central chest tightness, the same as her usual angina, with no radiation, no sweating and no shortness of breath.
Findings: Restoration in progress on tooth #30. She has complained of a persistent metallic, altered taste since her medication was changed some months ago, and of a dry mouth.
Show answer and explanation
Correct answer: C. It releases nitric oxide, which stimulates guanylyl cyclase and raises cGMP, producing venodilation
- A. Calcium channel blockade describes amlodipine and diltiazem, again preventive agents.
- B. Beta-1 blockade describes metoprolol and atenolol, used for angina PREVENTION rather than for acute relief.
- C. CORRECT. Nitroglycerin is metabolised to NITRIC OXIDE, which activates soluble GUANYLYL CYCLASE in vascular smooth muscle. The resulting rise in cGMP dephosphorylates myosin light chains and relaxes the muscle. The dominant effect at therapeutic doses is on the VENOUS side: venodilation reduces preload and therefore ventricular wall tension and myocardial oxygen DEMAND. Coronary dilation contributes, but demand reduction is the main mechanism.
- D. Cyclo-oxygenase inhibition describes her ASPIRIN, which prevents thrombotic events but does nothing for an acute anginal episode.
Note: Tolerance develops rapidly with continuous nitrate exposure, which is why long-acting nitrate regimens build in a nitrate-free interval each day. Headache from cerebral vasodilation is the commonest side effect and is expected rather than alarming.