A patient started on isosorbide mononitrate reports throbbing headaches shortly after taking the dose. What is the most appropriate advice?

• A. Stop taking the medicine immediately
• B. Advise the patient that this is a side effect and it is safe to continue; see GP if headaches persist
• C. Take an analgesic and continue
• D. Switch to a different anti-anginal without medical advice

Answer: (B)

Headache after taking a nitrate is a common, expected side effect caused by dilation of cerebral vessels. It is not dangerous and often improves with time as tolerance develops, so the most appropriate advice is to reassure the patient that this reaction is typical and it is safe to continue the medication. They should monitor the headaches and consult their GP if the headaches persist, worsen, or significantly affect daily activities, as a clinician can consider dose adjustment or a different regimen. Stopping the medicine or switching without medical guidance isn’t advised.