Organic nitrate

Glyceryl trinitrate (GTN)

Brand names: GTN spray, Nitrolingual, Transiderm-Nitro, Rectogesic

Adult dose

Dose: Sublingual: 400–800 micrograms (1–2 sprays/tabs) PRN. IV (acute coronary syndrome / pulmonary oedema): 10–200 micrograms/min infusion. Patch: 5–10mg/24h. Anal fissure (Rectogesic 0.4%): apply 1 inch BD

Route: SL/IV/Topical/PR

Frequency: PRN/continuous

Clinical pearls

Angina relief, acute pulmonary oedema, anal fissure
Provide nitrate-free interval to prevent tolerance
Ask about Viagra/PDE-5 use before giving

Contraindications

Marked hypotension/hypovolaemia
Severe aortic/mitral stenosis
Constrictive pericarditis
HOCM
Closed-angle glaucoma
Concurrent PDE-5 inhibitor (sildenafil etc)

Side effects

Hypotension
Headache
Flushing
Tachycardia
Methaemoglobinaemia (rare)
Tolerance (continuous use)

Interactions

PDE-5 inhibitors (severe hypotension — avoid for 24h after sildenafil/vardenafil, 48h after tadalafil)
Riociguat (avoid)

Monitoring

Reference: BNF; ESC ACS guidelines; NICE NG106; https://bnf.nice.org.uk/drugs/glyceryl-trinitrate/. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Kruis Score for Irritable Bowel Syndrome · Functional GI

Drugs

Pathways