2.6.1 Nitrates

General guidance

• Nitrates are used to relieve ischaemic pain. However, unwanted effects such as flushing, headache, and postural hypotension may limit therapy, especially when angina is severe or when patients are unusually sensitive to the effects of nitrates.
• Sublingual glyceryl trinitrate is one of the most effective drugs for providing rapid symptomatic relief of angina.
• The development of nitrate tolerance is a significant problem, in order to avoid this it is necessary to allow nitrate blood levels to fall during the period of least patient activity (usually night time). The continuous use of transdermal patches as twice daily modified release systems this and should be avoided.
• 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 to 8 hours each day usually maintains effectiveness in such patients.
• Conventional formulations of isosorbide mononitrate should not normally be given more than twice daily unless small doses are used. Modified release formulations should be given once daily only.
• There is no reliable data to indicate that there are any differences in compliance or patient acceptance between asymmetric dosed isosorbide mononitrate (8am and 2pm) and once daily modified release isosorbide mononitrate.
• Only consider the use of modified release products if the patient is unable to comply with twice daily asymmetrically dosed isosorbide mononitrate.
• A variety of modified release preparations are available which differ significantly in cost. If these are written generically the community pharmacist can select the brand which will be charged to the drugs budget - this may not be the cheapest equally effective product available. 

Recommended drugs

Glyceryl Trinitrate sublingual (tablets or spray) £

Isosorbide Mononitrate tablets (prescribe as Monomax) ££

Drug Traffic Light Key:

Green – On Formulary

Amber – Restricted use, see local guidelines      

Purple – Specialist use/initiation

Red – Non Formulary

Relative Costs Key (where indicated):

£££££ - high

£££ - moderate

£ - low