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2.6.1 Nitrates

Acute reliefGlyceryl trinitrate spray 400micrograms per metered dose; Dose:
Aerosol spray: spray 1-2 doses under tongue and then close mouth
If symptoms do not resolve, this may be repeated at 5 minute intervals for a total of 3 doses. If symptoms have not resolved after a total of 3 doses, the patient should seek prompt medical attention
Ongoing treatmentIsosorbide mononitrate m/r capsules 25mg, 40mg, 50mg, 60mg; m/r tablets 25mg, 40mg, 50mg, 60mgDose:
Prophylaxis of angina, 25-120mg once daily in the morning (lower doses can be prescribed for first 2-4 days to minimise possibility of headache

Prescribing Notes

  • NICE CG126  covers the management of stable angina.
  • Nitrates are used in the management of angina pectoris, unstable angina, heart failure and acute myocardial infarction.
  • Modified release nitrates should not be given more than once daily as nitrate tolerance will develop. A daily nitrate-free period is necessary to minimise tolerance. The length of the nitrate-free period required varies and depends on the pharmacokinetic properties of each preparation.
  • Asymmetric dosing regimens with standard-release nitrate preparations can be confusing to patients and could lead to non-compliance and nitrate tolerance. Consider switch to modified release preparation.
  • Glyceryl trinitrate patches are not recommended as they have no proven advantages over oral nitrates and cost much more. Unless patients remove patches for several consecutive hours per day (8-12 hours) nitrate tolerance can develop. Sensitivity to the patch adhesive may also occur.
  • Nitrates may occasionally aggravate angina in hypertrophic cardiomyopathy and increase intra-ocular pressure in glaucoma.
  • GTN intravenous injection may be given when GTN spray is ineffective in patients with chest pain due to myocardial infarction or severe ischaemia and in treatment of acute left ventricular failure.