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Nitrate / Acute Angina Pregnancy: §4.6 — Pregnancy: 'Developmental toxicity studies performed in rats and rabbits using various routes of administration did not reveal any effect on the embryos, fetuses or the young animals even at toxic doses for the dam.' Breast-feeding: 'Available evidence is inconclusive or inadequate for determining infant risk when used during breastfeeding. There is data that nitrates are excreted in breast milk and may cause methaemoglobinaemia in infants. The extent of excretion of nitroglycerin in human breast milk has not been determined. A risk to the suckling child cannot be excluded. A decision must be made whether to discontinue breast-feeding or to discontinue/abstain from Glyceryl Trinitrate therapy taking into account the benefit of breast feeding for the child and the benefit of therapy for the woman.' Fertility: reproduction toxicity studies in rats and rabbits revealed no effect on mating, fertility and general reproductive parameters; there are no human fertility data.

Glyceryl Trinitrate (Sublingual / IV)

Brand names: GTN spray (Nitrolingual), GTN tablets (Nitrostat), IV: Nitronal

Used in: Acute Coronary Syndrome & Chest Pain

Glyceryl trinitrate is a nitrate used sublingually (tablet or spray) for rapid relief of acute angina, and intravenously in acute settings such as pulmonary oedema and unstable angina.

Adult dose

Dose: INTRAVENOUS INFUSION ONLY — this dose covers ONE of the two routes this page carries. Unstable angina: an initial dose of 10 micrograms/min is recommended, with increments of 10 micrograms/min made at approximately 30 minute intervals according to the needs of the patient (SPC §4.2, heading 'Unstable angina'). The SPC's general adult statement is that 'The dose of Glyceryl Trinitrate should be adjusted to meet the individual needs of the patient. The recommended dosage range is 10 - 200 micrograms/min'. ⚠️ THE SUBLINGUAL SPRAY AND TABLET DOSES THIS PAGE ALSO COVERS ARE NOT SOURCED HERE — the fetched product is an intravenous infusion solution and says nothing about the sublingual route; the sublingual dose remains to be independently re-sourced and must not be inferred from the figures above.
Route: Intravenous infusion. §4.2: 'For intravenous use. Glyceryl Trinitrate should be administered by means of a micro-drip set infusion pump or similar device which permits maintenance of constant infusion rate.' It 'can be administered undiluted by slow intravenous infusion using a syringe pump incorporating a glass or rigid plastic syringe', or given as an admixture 'using a suitable vehicle such as Sodium Chloride Injection B.P. or Dextrose Injection B.P.'; prepared admixtures should be given by intravenous infusion or by syringe pump to ensure a constant rate. §4.4 states: 'Glyceryl Trinitrate should not be given by bolus injection.' The sublingual route this page also lists is NOT covered by this source.
Frequency: Continuous intravenous infusion at a constant rate, titrated to effect — for unstable angina, increments of 10 micrograms/min at approximately 30 minute intervals according to the needs of the patient (§4.2). §4.2 adds: 'During Glyceryl Trinitrate administration there should be close haemodynamic monitoring of the patient. The posology of Glyceryl Trinitrate i.v. should be adjusted to achieve the desired clinical response.'
Max: 200 micrograms/min — the top of the SPC's recommended adult range, §4.2 verbatim: 'The recommended dosage range is 10 - 200 micrograms/min but up to 400 micrograms/min may be necessary during some surgical procedures.' The 400 micrograms/min figure belongs to SURGICAL use and is deliberately NOT carried over as a ceiling for unstable angina.
INDICATION CONFIRMED BY §4.1 (newly captured), verbatim: 'The following indications exist for Glyceryl Trinitrate: • Unresponsive congestive heart failure, including that secondary to acute myocardial infarction; acute left-sided heart failure and acute myocardial infarction, • Refractory unstable angina pectoris and coronary insufficiency, including Prinzmetal's angina, • Control of hypertensive episodes and/or myocardial ischaemia during and after cardiac surgery, • Induction of controlled hypotension for surgery.' || THE PUBLISHED FIGURE, §4.2 VERBATIM (the audit trail for the dose above): 'Unstable angina: An initial dose of 10 micrograms/min is recommended with increments of 10 micrograms/min being made at approximately 30 minute intervals according to the needs of the patient.' And the range it sits in, §4.2 verbatim: 'Adults The dose of Glyceryl Trinitrate should be adjusted to meet the individual needs of the patient. The recommended dosage range is 10 - 200 micrograms/min but up to 400 micrograms/min may be necessary during some surgical procedures.' || SCOPE, STATED DELIBERATELY: only the INTRAVENOUS route is published. The page also covers a sublingual 400 microgram spray and sublingual tablets; no source in this bundle covers the sublingual route at all (the openFDA record is a US sublingual tablet label, but it gives only a COUNT of tablets across three unpinned strengths — 0.3 mg, 0.4 mg and 0.6 mg — so no milligram value can be attributed, and none has been). Nothing sublingual has been inferred from the infusion figures. || OTHER §4.2 REGIMENS PRESENT IN THIS LABEL BUT NOT PUBLISHED HERE, because they are different indications from this page's: 'Use in surgery A starting dose of 25 micrograms/min is recommended for the control of hypertension, or to produce hypotension during surgery. This may be increased by increments of 25 micrograms/min at 5 minute intervals until the blood pressure is stabilised.'; 'Myocardial ischaemia The treatment of perioperative myocardial ischaemia may be started with a dose of 15 - 20 micrograms/min, with subsequent increments of 10 - 15 micrograms/min until the required effect is obtained.'; 'Unresponsive congestive heart failure: The recommended starting dose is 20 - 25 micrograms/min. This may be decreased to 10 micrograms/min, or increased in steps of 20-25 micrograms/min every 15 - 30 minutes until the desired effect is obtained.' || PAEDIATRIC, §4.2 verbatim: 'The safety and efficacy of Glyceryl Trinitrate has not yet been established in children.' No paediatric figure is published and nothing has been scaled from the adult rate — verify any paediatric use against a children's formulary. || ELDERLY, §4.2 verbatim: 'There is no evidence that a posology adjustment is required in the elderly'. || ADMIXTURE EXAMPLE, §4.2 verbatim: 'To obtain an admixture of Glyceryl Trinitrate at a concentration of 100 micrograms/ml, add 50 ml Glyceryl Trinitrate solution (containing 50 mg glyceryl trinitrate) to 450 ml of infusion vehicle to give a final volume of 500 ml. A dosage of 100 micrograms/min. can be obtained by giving 60 ml of the admixture per hour.' Vials are for single use only and should not be regarded as multi-dose containers. || GIVING SET: §4.4 warns that PVC or polyurethane infusion material causes loss of active substance by adsorption and that 'If these materials are used the dose must be adjusted to suit patient's needs'; polyethylene, polypropylene or PTFE have proven suitable. || SOURCE COMPLETENESS: all six captured eMC sections (§4.1, §4.2, §4.3, §4.4 with the §4.5 interaction text appended, §4.6, §4.8) are complete and untruncated in this bundle.

Dose adjustments

Renal

§4.2 verbatim: 'Patients with renal and hepatic impairment Additional dose adjustments in patients with severe hepatic insufficiency or severe renal failure may be necessary and require additional monitoring.' §4.4 adds: 'Caution should be exercised in patients with severe liver or renal disease, hypothermia, hypothyroidism.' No numeric renal band or dose reduction is given in this SPC.

Hepatic

§4.2 verbatim: 'Patients with renal and hepatic impairment Additional dose adjustments in patients with severe hepatic insufficiency or severe renal failure may be necessary and require additional monitoring.' §4.4 adds: 'Caution should be exercised in patients with severe liver or renal disease, hypothermia, hypothyroidism.' No numeric hepatic band or dose reduction is given in this SPC.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Administer one tablet under the tongue or in the buccal pouch at the first sign of an acute anginal attack. Allow tablet to dissolve without swallowing. One additional tablet may be administered every 5 minutes until relief is obtained. No more than three tablets are recommended within a 15-minute period. If the pain persists after a total of 3 tablets in a 15-minute period, or if the pain is different than is typically experienced, seek prompt medical attention. Nitroglycerin sublingual tablets may be used prophylactically 5 to 10 minutes prior to engaging in activities that might precipitate an acute attack. For patients with xerostomia, a small sip of water prior to placing the tablet …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-10-15. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

  • Hypersensitivity to the active substance, other nitrates or any of the excipients listed in section 6.1 (§4.3)
  • Concurrent phosphodiesterase type 5 (PDE5) inhibitors — §4.3 verbatim: 'During nitrate therapy, phosphodiesterase inhibitors type 5 (PDE5) (e. g. sildenafil, vardenafil, tadalafil) must not be used because PDE5 inhibitors may amplify the vasodilatory effects of Glyceryl Trinitrate resulting in severe hypotension (see sections 4.4 and 4.5).' §4.4 gives the interval: glyceryl trinitrate 'must not be used in patients known to be taking phosphodiesterase inhibitor-containing products (e.g. sildenafil, vardenafil, tadalafil) in the intervening 24 hours (48 hours for tadalafil)'
  • Concurrent riociguat — §4.3: 'During nitrate therapy, the soluble guanylate cyclase stimulator riociguat must not be used'
  • Acute circulatory failure (shock, collapse) (§4.3)
  • Cardiogenic shock, 'unless a sufficient end-diastolic pressure is maintained by appropriate measures' (§4.3)
  • Uncorrected hypovolaemia and hypotensive shock (§4.3)
  • Severe anaemia (§4.3)
  • Severe cerebral haemorrhage (§4.3)
  • Head trauma (§4.3)
  • Conditions associated with an increased intracranial pressure (§4.3)
  • Arterial hypoxaemia, and angina caused by hypertrophic obstructive cardiomyopathy (§4.3)
  • Myocardial insufficiency due to obstruction — aortic or mitral stenosis, hypertrophic obstructive cardiomyopathy or constrictive pericarditis (§4.3)
  • Constrictive pericarditis (§4.3)
  • Pericardial tamponade (§4.3)
  • Toxic pulmonary oedema (§4.3)

Side effects

  • Headache — very common (§4.8). 'Like other nitrate preparations, Glyceryl Trinitrate commonly causes dose-dependent headaches due to cerebral vasodilation. These often regress after a few days despite the maintenance of therapy… Unresponsive headaches are an indication for reducing the dosage of Glyceryl Trinitrate or discontinuing treatment.'
  • Dizziness (including postural dizziness) and somnolence — common (§4.8)
  • Tachycardia — common (§4.8). 'A slight reflex-induced increase in heart rate can be avoided by resorting, if necessary, to combined treatment with a beta-blocker.'
  • Orthostatic hypotension — common; asthenia — common (§4.8)
  • Enhanced angina pectoris symptoms — uncommon (§4.8)
  • Circulatory collapse, sometimes accompanied by bradyarrhythmia and syncope — uncommon (§4.8)
  • Nausea and vomiting — uncommon; heartburn — very rare (§4.8)
  • Allergic skin reactions (e.g. rash) and allergic contact dermatitis — uncommon; pruritus, burning, erythema and irritation — uncommon (§4.8)
  • Flushing, hypotension, palpitations, increased heart rate, exfoliative dermatitis and generalised rash — frequency not known (§4.8)
  • Severe hypotensive responses (§4.8): 'Severe hypotensive responses have been reported for organic nitrates and include nausea, vomiting, restlessness, pallor and excessive perspiration.'
  • Temporary hypoxaemia due to relative redistribution of blood flow in hypoventilated alveolar areas, which in coronary artery disease may lead to myocardial hypoxia (§4.8)
  • Methaemoglobinaemia has been reported following treatment (§4.4)

Interactions

  • PDE5 inhibitors (sildenafil, vardenafil, tadalafil) — §4.5: the blood-pressure-lowering effect is increased and 'This might lead to life threatening cardiovascular complications'; patients who have recently taken them must not be treated with glyceryl trinitrate in the intervening 24 hours (48 hours for tadalafil), and patients on nitrate therapy must not use them
  • Riociguat — concomitant use is contraindicated since it can cause hypotension (§4.5)
  • Other vasodilators, calcium channel antagonists, ACE inhibitors, monoamine oxidase inhibitors, beta-blockers, diuretics, antihypertensives, tricyclic antidepressants and neuroleptics, and alcohol, may potentiate the hypotensive effect (§4.5)
  • Tissue plasminogen activator (tPA) — simultaneous intravenous infusions 'may accelerate plasma clearance of tPA by increasing hepatic blood flow' (§4.5)
  • Dihydroergotamine — glyceryl trinitrate may increase its blood level and effect; dihydroergotamine antagonises glyceryl trinitrate and may lead to coronary vasoconstriction, warranting special attention in coronary artery disease (§4.5)
  • Heparin — 'The use of heparin and Glyceryl Trinitrate solution can lead to a partial loss of action of heparin when both drugs are given simultaneously by intravenous route' (§4.5)
  • Acetylsalicylic acid may potentiate the blood-pressure-lowering effect; NSAIDs other than acetylsalicylic acid may diminish the therapeutic response (§4.5)
  • Sapropterin (tetrahydrobiopterin, BH4) — caution during concomitant use with agents that cause vasodilation via nitric oxide, including glyceryl trinitrate (§4.5)

Monitoring

  • §4.2: 'During Glyceryl Trinitrate administration there should be close haemodynamic monitoring of the patient. The posology of Glyceryl Trinitrate i.v. should be adjusted to achieve the desired clinical response.'
  • §4.4: 'Reducing systolic blood-pressure below 90 mmHg must be avoided' — stated for patients with low filling pressures, e.g. acute myocardial infarction and impaired left ventricular function
  • §4.4: particular caution and medical supervision in low filling pressures and in orthostatic dysfunction; tolerance and cross-tolerance to other nitro compounds has been described
  • §4.4: watch for methaemoglobinaemia — and note that methylene blue is contraindicated as treatment in glucose-6-phosphate deficiency or methaemoglobin-reductase deficiency
  • §4.4: caution in arterial hypoxaemia due to severe anaemia (including G6PD-deficiency-induced forms), and in hypoxaemia with ventilation/perfusion imbalance due to lung disease or ischaemic heart failure — nitroglycerin 'could reverse this protective vasoconstriction and thus result in increased perfusion of poorly ventilated areas, worsening of the ventilation/perfusion imbalance, and a further decrease in the arterial partial pressure of oxygen'
  • §4.4: infusion material made of PVC or polyurethane causes loss of active substance by adsorption — 'If these materials are used the dose must be adjusted to suit patient's needs'; polyethylene, polypropylene or PTFE are suitable
  • §4.4: the solution contains glucose — take this into account in patients with diabetes mellitus
  • §4.4: avoid alcohol during treatment, as it may potentiate the hypotensive and vasodilating effect
  • §4.4: 'Glyceryl Trinitrate should not be given by bolus injection.'

Clinical monograph

How it works

It is converted to nitric oxide, causing venodilatation (reducing preload) and coronary vasodilatation, which lowers myocardial oxygen demand and relieves ischaemic pain.

Prescribing in practice

  • Headache, flushing and hypotension are common.
  • Tolerance develops with continuous exposure, so a nitrate-free interval is used for regular nitrate therapy.
  • It is contraindicated with PDE5 inhibitors (e.g. sildenafil), which together cause profound hypotension.

Monitoring

Monitor blood pressure and symptom response, particularly with intravenous use.

Counselling the patient

  • For an attack, sit down and use it; repeat as advised and call emergency services if pain persists after the advised doses/time.
  • A brief headache is common.
  • Never use it with erectile-dysfunction tablets such as sildenafil.

Evidence & guidelines

Standard for acute angina relief and used intravenously in acute cardiac care.

Reference: ESC Stable CAD Guidelines 2019; NICE CG126 (Stable Angina); NICE NG185 (ACS); SPC Nitrolingual; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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