Nitroglycerin

Organic nitrate, Vasodilator, Antianginal

Nitroglycerin (glyceryl trinitrate, GTN)

Nitrostat, Nitrolingual, NitroMist, Nitro-Bid, Nitro-Dur, Minitran, Rectiv

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Summary

Classes

Organic nitrate, Vasodilator, Antianginal

Pharmacy

Starting dose

SL 0.3-0.6 mg every 5 minutes up to 3 doses for acute angina (call EMS if not resolved after the third); IV infusion 5-10 mcg/min titrated; transdermal patch 0.2-0.4 mg/hr for 12-14 hours daily (nitrate-free interval prevents tolerance)

Preparations

SL 0.3, 0.4, 0.6 mg tablets; lingual spray 0.4 mg/spray; ER 2.5-9 mg capsules; transdermal patch 0.1-0.8 mg/hr; 2% ointment; 0.4% rectal ointment; 5 mg/mL IV

US FDA Max

Indication-specific; titrated to effect

Pharmacology

Routes

Sublingual, lingual spray, oral ER, transdermal, topical, rectal, IV

Onset

SL/spray: 1-3 minutes; IV: minutes; patch: 30-60 minutes

Duration

SL: 30 minutes; patch: 12-14 hours; IV continuous

Half-life

1-3 minutes (very short)

Bioavailability

Highly route-dependent: SL bypasses first-pass; oral has extensive first-pass (used only for chronic ER preparations); transdermal predictable

Pregnancy

Used in obstetric emergencies (uterine relaxation, severe hypertension) when needed; otherwise limited routine use.^{[citation needed]}

Legal status

Rx-only in US

Purported mechanism

Nitroglycerin is enzymatically denitrated (largely by mitochondrial aldehyde dehydrogenase, ALDH2) to release nitric oxide (NO), which activates soluble guanylyl cyclase, raises cGMP, and relaxes vascular smooth muscle predominantly in the venous capacitance bed (preload reduction) at low doses, with arterial vasodilation at higher doses.▲0▼ Phosphodiesterase-5 inhibitors (sildenafil, tadalafil, vardenafil) catastrophically potentiate nitrate-induced hypotension — concurrent use is absolutely contraindicated. Tolerance develops rapidly with continuous exposure; daily nitrate-free intervals (typically 8-12 hours) restore responsiveness.