Nitrates · Cardiovascular
Nitroglycerin (glyceryl trinitrate)
GTN · glyceryl trinitrate · nitro · Nitrostat® · Nitrolingual® · Nitro-Dur®(brand names vary by market)
Preload relief in ninety seconds, and gone in twenty minutes.
Also: oral liquid, patch, infusion
Mechanism
Metabolised to nitric oxide in vascular smooth muscle, raising cyclic GMP and relaxing veins first, arteries later. Most anginal relief comes from the fall in preload, not from coronary dilation.
Indications
- Acute angina
- Angina prophylaxis before exertion
- Acute heart failure with hypertension
- Hypertensive emergency (infusion)
Formulations
Dosing concepts
Sublingual
One dose, then wait; repeat at intervals up to a stated maximum, and if pain persists beyond that the patient is calling emergency services, not taking a fourth.
Tolerance
Continuous exposure produces tolerance within a day, so patches are removed for a nitrate-free interval each night and long-acting oral regimens are dosed asymmetrically.
Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.
Pharmacokinetics
- Bioavailability
- Sublingual bypasses a near-total first-pass effect
- Half-life
- 1 to 4 min
- Elimination
- hepatic: Extremely rapid; the clinical duration comes from the tissue effect, not the plasma level
Adverse effects
- HeadachecommonVery common, often severe at first, and usually settles within days. Warning the patient is what keeps them taking it.
- Hypotension and dizzinesscommon & serious
- Reflex tachycardiacommon
- SyncopeseriousWhich is why the first sublingual dose is taken sitting down.
Contraindications & precautions
Contraindications
- Any phosphodiesterase-5 inhibitor within the interaction window
- Severe aortic stenosis
- Hypertrophic obstructive cardiomyopathy
- Right ventricular infarction
- Hypotension
Precautions
- Volume depletion
- Recent inferior myocardial infarction
- Raised intracranial pressure
Interactions
No curated interaction entries yet for this agent.
Monitoring
Blood pressure, especially with the first dose and with infusions
Hypotension is the dose-limiting effect
How many sublingual doses per week
A rising requirement is a change in the disease, not a change in the drug
Headache
The commonest reason for non-adherence, and it is manageable
Counselling points
- Sit down before taking a sublingual dose.
- If the pain is not gone after the stated number of doses, call emergency services. Do not keep taking more.
- Headache is common at first and usually settles; simple analgesia helps.
- Never take this with a medicine for erectile dysfunction. Ask us if you are unsure which those are.
- Sprays and tablets have expiry dates that matter; a tablet that no longer stings may no longer work.
Clinical pearls
- In inferior myocardial infarction with right ventricular involvement, the right ventricle is preload-dependent and nitrate can cause abrupt, profound hypotension. Right-sided leads before nitrate is a real clinical habit.
- A patient who has quietly increased from two sprays a month to two a day has unstable angina, and the medication history is what reveals it.
References & review
- Nitroglycerin product monograph (consult the current version for your market) (monograph)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)
Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.