If a patient on isosorbide mononitrate reports headaches shortly after dosing, what is the recommended course of action?

• A. These headaches are an expected side effect; continue therapy and seek GP advice if they persist
• B. Stop the medication immediately
• C. Take an additional nitrate dose to relieve the headache
• D. Do nothing and monitor symptoms

Answer: (A)

Headache is a common, expected adverse effect of nitrate therapy because these drugs dilate cerebral vessels. When starting isosorbide mononitrate or increasing the dose, headaches often appear shortly after dosing but tend to improve over time or with dose adjustment. Because the goal is to maintain anti-anginal protection, the best course is to continue the nitrate and manage the symptom rather than stopping treatment. If the headaches persist or are troublesome, a GP can adjust the dose or timing or suggest a simple analgesic; avoid taking extra nitrate doses to relieve the headache and avoid stopping the medication abruptly.