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Nitrate (vasodilator) Pregnancy: UK SPC §4.6 (infusion), verbatim: '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.' No human pregnancy statement is given. 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...' Fertility: reproduction toxicity studies 'did not reveal any effect on mating, fertility and general reproductive parameters'; there is no human fertility data. US sublingual-tablet label §8.1: 'Limited published data on the use of nitroglycerin are insufficient to determine a drug associated risk of major birth defects or miscarriage.'

Glyceryl Trinitrate (GTN)

Brand names: Nitrolingual, GTN 400 Spray, Nitro-Dur, Minitran

Glyceryl trinitrate (GTN) is a nitrate vasodilator used in the emergency management of acute coronary syndromes, acute pulmonary oedema and to relieve angina, available in sublingual and intravenous forms.

Adult dose

Dose: Acute anginal attack, sublingual (US label): one nitroglycerin sublingual tablet - the product is supplied as 0.3 mg, 0.4 mg and 0.6 mg tablets - under the tongue or in the buccal pouch at the first sign of an attack. Intravenous infusion (UK SPC): 10 - 200 micrograms/min, adjusted to the individual patient; unstable angina, an initial dose of 10 micrograms/min; unresponsive congestive heart failure, a starting dose of 20 - 25 micrograms/min.
Route: Sublingual / buccal tablet, and intravenous infusion by pump. SCOPE - these are the only two routes the fetched sources cover. The metered sublingual spray and the transdermal patches listed on this page are NOT covered: neither product was fetched, so no per-spray or per-patch dose is asserted here (in particular, the 400 micrograms-per-spray figure on the current page comes from the brand name, not from any fetched source).
Frequency: Sublingual: at the onset of an attack, then 'One additional tablet may be administered every 5 minutes until relief is obtained'; may also be used prophylactically '5 to 10 minutes prior to engaging in activities that might precipitate an acute attack'. Intravenous: continuous infusion at a constant rate, adjusted to clinical response.
Max: Maximum for the sublingual dose shown - US label: 'No more than three tablets are recommended within a 15-minute period', and '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.' No maximum dose is stated for the intravenous infusion.
Verbatim, US sublingual-tablet label §2: '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... Administer nitroglycerin sublingual tablets at rest, preferably in the sitting position.' Strengths are pinned by §3: 'Sublingual tablets, 0.3 mg; 0.4 mg; 0.6 mg'. Verbatim, UK SPC §4.2 (infusion): '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.' Indication-specific starting rates in the same SPC: 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'; 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'. The 400 micrograms/min figure is an infusion RATE quoted for surgical procedures, not a ceiling, which is why it is not in maxDose. Administration: 'Glyceryl Trinitrate should not be given by bolus injection'; give 'by means of a micro-drip set infusion pump or similar device which permits maintenance of constant infusion rate'. Dilution example from §4.2: '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.' PAEDIATRIC: paedDose is null because both labels decline to dose children - UK SPC §4.2 'The safety and efficacy of Glyceryl Trinitrate has not yet been established in children'; US label §8.4 'The safety and effectiveness of nitroglycerin in pediatric patients have not been established.' ELDERLY: UK SPC §4.2 'There is no evidence that a posology adjustment is required in the elderly'; the US label advises cautious dose selection, 'usually starting at the low end of the dosing range'.

Dose adjustments

Renal

UK SPC §4.2: 'Additional dose adjustments in patients with severe hepatic insufficiency or severe renal failure may be necessary and require additional monitoring.' No numeric adjustment is given. §4.4 adds: 'Caution should be exercised in patients with severe liver or renal disease, hypothermia, hypothyroidism.' The US sublingual-tablet label carries no renal dosing statement in any fetched section.

Hepatic

UK SPC §4.2: 'Additional dose adjustments in patients with severe hepatic insufficiency or severe renal failure may be necessary and require additional monitoring.' No numeric adjustment is given; §4.4 repeats that caution is needed in severe liver disease. The US sublingual-tablet label carries no hepatic dosing statement in any fetched section.

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.

Contraindications

  • UK SPC §4.3: 'Hypersensitivity to the active substance, other nitrates or any of the excipients listed in Section 6.1'
  • UK SPC §4.3: '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'; §4.4 adds it 'must not be used in patients known to be taking phosphodiesterase inhibitor-containing products ... in the intervening 24 hours (48 hours for tadalafil)'
  • UK SPC §4.3: 'During nitrate therapy, the soluble guanylate cyclase stimulator riociguat must not be used'
  • UK SPC §4.3: 'Acute circulatory failure (shock, collapse)' and 'Cardiogenic shock (unless a sufficient end-diastolic pressure is maintained by appropriate measures)'
  • UK SPC §4.3: 'Uncorrected hypovolaemia and hypotensive shock'
  • UK SPC §4.3: 'Severe anaemia' - the US label explains that 'large doses of nitroglycerin may cause oxidation of hemoglobin to methemoglobin and could exacerbate anemia'
  • UK SPC §4.3: 'Severe cerebral haemorrhage', 'Head trauma' and 'Conditions associated with an increased intracranial pressure'
  • UK SPC §4.3: 'Arterial hypoxaemia and angina caused by hypertrophic obstructive cardiomyopathy'
  • UK SPC §4.3: 'Myocardial insufficiency due to obstruction, aortic or mitral stenosis, hypertrophic obstructive cardiomyopathy or constrictive pericarditis'
  • UK SPC §4.3: 'Constrictive pericarditis' and 'Pericardial tamponade'
  • UK SPC §4.3: 'Toxic pulmonary oedema'

Side effects

  • Very common (>=1/10), UK SPC §4.8: headache - '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.'
  • Common (>=1/100 to <1/10), UK SPC §4.8: dizziness (including postural dizziness), somnolence; tachycardia; orthostatic hypotension; asthenia
  • Uncommon (>=1/1,000 to <1/100), UK SPC §4.8: enhanced angina pectoris symptoms; circulatory collapse (sometimes accompanied by bradyarrhythmia and syncope); nausea, vomiting; allergic skin reactions (e.g. rash) and allergic contact dermatitis; pruritus, burning, erythema and irritation
  • Very rare (<1/10,000), UK SPC §4.8: heartburn
  • Frequency not known, UK SPC §4.8: palpitations; flushing; hypotension; exfoliative dermatitis; generalised rash; increased heart rate
  • UK SPC §4.8: 'Severe hypotensive responses have been reported for organic nitrates and include nausea, vomiting, restlessness, pallor and excessive perspiration.'
  • UK SPC §4.8: 'During treatment with Glyceryl Trinitrate, a temporary hypoxemia may occur due to a relative redistribution of the blood flow in hypoventilated alveolar areas. Particularly in patients with coronary artery disease this may lead to a myocardial hypoxia.'
  • UK SPC §4.4: methaemoglobinaemia has been reported - and 'Treatment of methaemoglobinaemia with methylene blue is contraindicated in patients with glucose-6-phosphate deficiency or methaemoglobin-reductase deficiency'
  • US label §6: 'Most common adverse reactions occurring at a frequency greater than 2% are headache, dizziness and paresthesia'; also vertigo, weakness, palpitation and other manifestations of postural hypotension, syncope, flushing, drug rash and exfoliative dermatitis
  • Tolerance, UK SPC §4.4: 'The development of tolerance and cross tolerance to other nitro compounds has been described.' US label §5.1: 'Excessive use may lead to the development of tolerance. Only the smallest dose required for effective relief of the acute angina attack should be used.'

Monitoring

  • UK SPC §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.'
  • UK SPC §4.4: in low filling pressures - e.g. acute myocardial infarction or impaired left ventricular function - 'Reducing systolic blood-pressure below 90 mmHg must be avoided'.
  • UK SPC §4.2: 'Additional dose adjustments in patients with severe hepatic insufficiency or severe renal failure may be necessary and require additional monitoring.'
  • Watch for methaemoglobinaemia (UK SPC §4.4) and for the temporary hypoxaemia / ventilation-perfusion mismatch described in §4.4 and §4.8, particularly in patients with severe anaemia (including G6PD-deficiency forms), lung disease or ischaemic heart failure.
  • US label §2 (sublingual): if pain persists after a total of 3 tablets in a 15-minute period, or if the pain differs from what is typically experienced, seek prompt medical attention.
  • Ask about PDE-5 inhibitors and riociguat before every dose - UK SPC §4.4 requires patients on GTN to be warned not to take PDE-5 inhibitor products.
  • Infusion set material, UK SPC §4.4: PVC or polyurethane 'has been shown to induce a loss of the active substance due to adsorption. If these materials are used the dose must be adjusted to suit patient's needs.'

Clinical monograph

How it works

It is converted to nitric oxide, which raises vascular smooth muscle cyclic GMP and produces venous and arterial dilatation, reducing cardiac preload and afterload and improving coronary perfusion.

Prescribing in practice

  • It is contraindicated with phosphodiesterase-5 inhibitors such as sildenafil and tadalafil, as the combination can cause profound, refractory hypotension.
  • Avoid in haemodynamic states dependent on preload, such as significant aortic stenosis, hypertrophic obstructive cardiomyopathy and right ventricular infarction, where it may cause severe hypotension.
  • Intravenous infusion requires close blood-pressure titration, and tolerance can develop with continuous use.

Monitoring

Monitor blood pressure and heart rate closely, with continuous monitoring during intravenous infusion.

Counselling the patient

  • Sublingual GTN can cause a brief headache, flushing or light-headedness; sit down when using it.
  • Never use this within a day of erectile-dysfunction tablets such as sildenafil.
  • If chest pain persists despite repeated doses, call for emergency help.

Evidence & guidelines

Nitrates for acute coronary syndromes and acute pulmonary oedema are supported by NICE and ESC guidance.

Reference: NICE NG185 ACS; ESC STEMI/NSTE-ACS Guidelines; 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.

Pathways