gtn spray

presentation - what the drug is sealed in, its concentration and how it might look

Glycerol Trinitrate (GTN) can come in many presentations such as tablets or suppositories, however most NHS and private ambulance services exclusively use sprays. However, be aware you may encounter patient’s who have been prescribed the tablet form instead of the spray and you can encourage them to take these if it is indicate and no contra-indications are apparrent.

  • Sublingual spray containing 400 micrograms glyceryl trinitrate per metered dose.

  • Sublingual tablets containing glyceryl trinitrate 300, 500 or 600 micrograms per tablet.

INDICATIONS - reasons you should administer this drug

  • Cardiac chest pain due to angina or myocardial infarction, when systolic blood pressure is greater than 90mmHg.

    • As it dilates the coronary blood vessels potentially allowing more blood to pass by the blockage.

  • Consider administering GTN in Acute Heart Failure with ischaemia or uncontrolled hypertension.

    • In heart failure it can widen the pulmonary blood vessels creating a potential space for the pulmonary oedema to move to.

    • “Uncontrolled hypertension” also known as a hypertensive emergency is anyone presenting with a BP of >180/120mmHg AND is symptomatic i.e. blurred vision, headache, nausea, chest pain, dizziness, seizures or CVE symptoms (BEFAST).

  • Patients with suspected cocaine toxicity presenting with chest pain.

    • The cocaine, particularly when taken with alcohol (coca-ethylene poisoning) can restrict coronary blood vessels.

CONTRAINDICATIONS - reasons you should not administer this drug

  • Hypotension (systolic blood pressure < 90mmHg in angina/myocardial infarction, or < 110 mmHg in acute heart failure).

  • Hypovolaemia.

  • Head trauma.

  • Cerebral haemorrhage.

  • Sildenafil (Viagra) and other related drugs – glyceryl trinitrate must not be given to patients who have taken sildenafil or related drugs within the previous 24 hours.

  • Profound hypotension may occur.

  • Unconscious patients.

  • Known severe aortic or mitral stenosis.

cautions - reasons that if you administer this drug you must monitor for side effects more than usual

  • Patients with suspected posterior myocardial infarction or right-ventricular infarction.

    • ST elevation and/or depression in leads ii, iii, AVF confirmed by V4R.

    • GTN can already induce hypotension through systemic vasodilation which can in turn lead to reduced pre-load (the amount of blood entering the heart); it is thought that this reduced pre-load combined with a weakened or damaged right ventricle can exacerbate hypotension further as the right ventricle is increasingly unable to pump blood to the left ventricle leading to increased mortality. I.e. only administer with a systolic >110 systolic and with close monitoring.

  • NB: To reduce the risk of cross-contamination between patients, the nozzle of the spray must not come into contact with the patient’s mouth. Wipe after each use with a detergent wipe.

pharmacological action - what does it to the body and what does the body do to it?

FREC 3 and FREC 4:

A potent vasodilator drug resulting in:

  • Dilatation of coronary arteries/relief of coronary spasm.

  • Dilatation of systemic veins resulting in lower pre-load.

  • Reduced blood pressure.

FREUC 5 and L4 AAP

Pharmacokinetics:

  • Absorption: Sublingual. Onset ~1–2 minutes; peak ~5 minutes; duration ~20–30 minutes. Bypasses first-pass metabolism.

  • Distribution: Highly lipid-soluble; ~60% protein binding; rapid distribution into vascular smooth muscle.

  • Metabolism: Extensive hepatic and intravascular metabolism via nitrate reductase to dinitrate and mononitrate metabolites.

  • Elimination: Metabolites excreted renally; plasma half-life ~1–4 minutes (very short).

Pharmacodynamics

  • Class: Organic nitrate vasodilator.

  • Mechanism: Converted to nitric oxide (NO) in vascular smooth muscle → smooth muscle relaxation.

  • Effects:

    • Venodilation → reduced preload → reduced myocardial oxygen demand.

    • Mild arterial dilation → reduced afterload.

    • Coronary vasodilation → improved myocardial perfusion.

    • Risks: hypotension, headache, reflex tachycardia.

side effects - unwanted secondary effects of this drug

  • Headache.

  • Dizziness.

  • Hypotension

dosage and administration - how much do we give and how do we give it?

Adults:

The oral mucosa must be moist for GTN absorption, moisten if necessary.

ANGINA, MYOCARDIAL INFARCTION or SUSPECTED COCAINE TOXICITY (systolic BP >90 mmHg)

  • Route: Sublingual (spray) or Oral (tablet)

  • Initial dose: 600mcg (tablet) or 400mcg (spray)

  • Repeat dose: 600mcg (tablet) or 400mcg (spray)

  • Dose Interval: 5 - 10 minutes

  • Concentration: 600mcg (tablet) or 400mcg (spray)

  • Volume: 1 tablet or 1 spray

  • Max dose: No Limit

NB: The effect of the first dose should be assessed over 5 minutes; further doses can be administered provided the systolic blood pressure is >90 mmHg. Remove the tablet if side effects occur, for example, hypotension.

ACUTE HEART FAILURE

Route: Sublingual (spray) or Oral (tablet)

  • Initial dose: 600mcg (tablet) or 400mcg (spray)

  • Repeat dose: 600mcg (tablet) or 400mcg (spray)

  • Dose Interval: 5 - 10 minutes

  • Concentration: 600mcg (tablet) or 400mcg (spray)

  • Volume: 1 tablet or 1 spray

  • Max dose: 1.8mg (3 tablets or 4 sprays)

NB: The effect of the first dose should be assessed over 5 minutes; further doses can be administered provided the systolic blood pressure is >110 mmHg. Remove the tablet if side effects occur, for example, hypotension.

Children:

See JRCALC for paediatric drug dosages

legislation and regulations - what legal class of drug is it, who can possess it and who can give it?

GTN is both a Prescription-Only (POM) and a Pharmacy Only (P) medicine. It is a Safe Administration of Lifesaving Medications drug (SALM) also. It is not a Controlled Drug. Therefore:

  • Prescription-Only Medicine (POM):

    • Some GTN formulations (for example transdermal patches, rectal ointment and certain oral preparations) are classified as POMs.

    • POMs would normally require a prescription from an authorised prescriber such as a medical doctor or Advanced Paramedic.

  • Pharmacy only (P):

    • Standard sublingual GTN spray (and many sublingual tablets) for angina are classified as Pharmacy (P) medicines.

    • P medicines do not require a prescription but must be supplied under the supervision of a pharmacist.

    • Paramedics and SALM-trained providers will usually obtain GTN spray via their employer or a supplying pharmacy and then use it within the limits of their role, training and local clinical guidelines / PGDs. In this instance, GTN is not a controlled drug so possession is not a legal issue here, as long as a Pharmacist supplied it.

  • Safe Administration of Lifesaving Medications (SALM):

    • SALM training does not itself create a new legal exemption, but it provides the competence and governance framework for organisations to allow non-prescribers to possess and administer GTN (for example via PGDs or written directions).

NB: Administration must still follow local clinical guidelines, governance processes and organisational policy.

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