Glyceryl Trinitrate [GTN], Isosorbide Dinitrate, Isosorbide Mononitrate |
Issues for Surgery |
For treatment of angina – exacerbation of symptoms if omitted. Risk of tachycardia and hypotension if continued. |
Advice in the Perioperative period |
Elective and Emergency Surgery Continue – monitor heart rate and blood pressure (BP). Post-operative Advice Restart post-operatively as soon as next dose is due. |
Interaction(s) with Common Anaesthetic Agents |
Hypotension Nitrates can increase the risk of hypotension when used concomitantly with inhalational or intravenous anaesthetics1, 2. Sympathomimetics Isosorbide dinitrate can act as a physiological antagonist to noradrenaline / norepinephrine3. |
Interaction(s) with other Common Medicines used in the Perioperative Period |
Hypotension Nitrates can increase the risk of hypotension when used concomitantly with the antiemetics droperidol and prochlorperazine1, 2, 3. |
Further Information |
Tolerance Many patients on long-acting or transdermal nitrates rapidly develop tolerance (with reduced therapeutic effects). Reduction of blood-nitrate concentrations to low levels for 4-12 hours each day usually maintains effectiveness. If tolerance is suspected during use of transdermal patches, they should be left off for 8-12 hours (usually overnight)1, 4. For patients on modified-release (MR) isosorbide dinitrate or standard release isosorbide mononitrate (ISMN), the second of the two daily doses should be given no later than 8 hours after the morning dose. MR preparations of ISMN should only be given once daily, and used in this way do not produce tolerance1. Ensure that nitrate-based medicines are prescribed accurately and appropriately.
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References |
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