From the Guidelines
No, you do not need to discontinue PRN nitroglycerin when prescribing Imdur (isosorbide mononitrate). These medications can be used together as part of a comprehensive angina management plan. Imdur is a long-acting nitrate typically taken once daily (usually 30-60 mg) to provide sustained nitric oxide release for angina prevention, while sublingual nitroglycerin (0.3-0.6 mg as needed) serves as rescue therapy for acute angina episodes. The combination is actually beneficial because Imdur provides baseline angina prophylaxis while nitroglycerin addresses breakthrough symptoms. According to the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes, all patients who are post–NSTE-ACS should be given sublingual or spray nitroglycerin with verbal and written instructions for its use 1.
Key points to consider when using Imdur and PRN nitroglycerin together include:
- Monitoring for potential additive hypotensive effects when both medications are used concurrently
- Ensuring proper nitrate-free intervals with Imdur (typically taken in the morning with the effect wearing off overnight) to prevent nitrate tolerance
- Educating patients about proper nitroglycerin administration, including taking it at the first sign of chest pain, sitting down when using it due to potential blood pressure drops, and seeking emergency care if pain persists after three doses over 15 minutes. The guideline also recommends that patients be informed about symptoms of worsening myocardial ischemia and MI and should be given verbal and written instructions about how and when to seek emergency care for such symptoms 1.
Overall, the combination of Imdur and PRN nitroglycerin can be an effective strategy for managing angina, and patients should be educated on the proper use of these medications to maximize their benefits while minimizing potential risks.
From the Research
Imdur and Nitroglycerin Usage
- When prescribing Imdur, it is not necessary to discontinue PRN nitroglycerin, as Imdur is used for the long-term management of angina pectoris, while nitroglycerin is used for the acute relief of angina symptoms 2, 3.
- Imdur provides effective antianginal prophylaxis for up to 12 hours and does not seem to be associated with rebound phenomena at the end of the dosage interval 2, 3.
- Nitroglycerin can still be used as needed for acute angina attacks, and its use is not affected by the concurrent use of Imdur 4, 5.
Nitrate Tolerance
- Nitrate tolerance can occur with continuous therapy, but it can be avoided by using nitrates intermittently with long nitrate-free intervals 4, 5.
- Imdur, which is a sustained-release formulation of isosorbide 5-mononitrate, can help prevent nitrate tolerance when used once daily 2, 3, 5.
- The use of Imdur does not seem to affect the efficacy of nitroglycerin when used for acute angina relief 4, 5.