Drug reference

Nitroglycerin

Nitrate vasodilator / antianginal · Antianginal

Also known as Glyceryl Trinitrate, GTN

START

Acute: 0.3-0.4 mg SL at chest pain onset, sit down, repeat every 5 min x 3 if needed, call EMS if no relief after 3 doses. Prophylaxis: lowest effective dose with 10-12h nitrate-free interval to prevent tolerance

TYPICAL MAX

SL: 1.8 mg in 15 min (3 doses). IV: 200 mcg/min

STOP IF

SBP <90 mmHg, severe headache, syncope, methemoglobinemia (cyanosis, chocolate-colored blood)

WATCH

BP and HR (especially with first dose and dose increases), headache severity, signs of tolerance, ensure nitrate-free interval for long-acting forms

CDSCO approvedSchedule HJan AushadhiNPPA price-controlledATC C01DA02

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 3min · SL: 1-3 minutes
PEAK: 6min · SL: 4-8 minutes
t½: 3min · 1-4 minutes (very short)
DURATION: 1h · SL: 30-60 minutes

EXCRETION

Renal (metabolites)

route + CYP

INTERACTIONS

10 major

incl. contraindicated

PREGNANCY

Use only if clearly needed; animal studies show adverse effects; nitrates used in pregnancy for hypertensive emergencies and uterine relaxation

FDA category + note

Top interactionssee all 12 →

SildenafilContraindicatedTextbook-citedKDT 7e · p950
TadalafilContraindicatedTextbook-citedKDT 7e · p950
Pde5 InhibitorsContraindicatedDatabaseKimi deep-research + Cla
AvanafilSevereDatabaseDDInter

Available in India

212 branded formulations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Converted to nitric oxide (NO) in vascular smooth muscle, activating guanylate cyclase and increasing cGMP, leading to vasodilation. Predominantly venodilator at low doses (reduces preload) with arterial vasodilation at higher doses (reduces afterload). Also causes coronary vasodilation, improving myocardial oxygen supply.

Indications

Acute angina pectoris (sublingual, spray)Angina prophylaxis (long-acting oral, transdermal, ointment)Acute coronary syndrome (IV)Hypertensive emergency (IV)Acute pulmonary edema / heart failure (IV)Anal fissure (topical ointment - off-label)

Dosing

Adult: Acute angina: 0.3-0.6 mg SL (may repeat x3 at 5-min intervals). Prophylaxis: 2.5-9 mg PO TDS-QDS (sustained-release); 0.2-0.8 mg/hr patch (12-14h on, 10-12h off). IV: 5 mcg/min, titrate by 5 mcg/min every 3-5 min (max 200 mcg/min)
Pediatric: Not recommended for angina in children; IV use in pediatric cardiac surgery: specialized dosing
Renal adjustment: No adjustment needed
Hepatic adjustment: No adjustment needed; extensive first-pass metabolism actually reduced in hepatic impairment (monitor for increased effect)
Geriatric: Start low; increased sensitivity to hypotension and falls
Max dose: SL: 1.8 mg in 15 minutes (3 tablets). IV: 200 mcg/min. Oral SR: 26 mg QDS

Pharmacokinetics

Onset

SL: 1-3 minutes; Spray: 2 minutes; IV: immediate; Oral SR: 20-45 minutes; Patch: 30-60 minutes

Peak effect

SL: 4-8 minutes; IV: immediate

Duration

SL: 30-60 minutes; IV: 1-5 minutes after stopping; Patch: 18-24 hours (but tolerance develops >12-14h continuous)

Half-life

1-4 minutes (very short - parent compound)

Bioavailability

SL: ~40%; Oral: <1% (extensive first-pass); Transdermal: variable

Protein binding

60%

Metabolism

Hepatic rapid metabolism by organic nitrate reductases to 1,2-glyceryl dinitrate and 1,3-glyceryl dinitrate (active metabolites)

Excretion

Renal (primarily as metabolites)

Contraindications

Hypersensitivity to nitrates
Severe hypotension (SBP <90 mmHg)
Cardiogenic shock
Severe aortic stenosis
Severe mitral stenosis
Hypertrophic obstructive cardiomyopathy (HOCM)
Constrictive pericarditis
Cardiac tamponade
Concurrent use with PDE5 inhibitors (sildenafil, tadalafil, vardenafil) - within 24-48h
Increased intracranial pressure
Severe anemia

Side effects

Common

Headache (most common - dose-related, usually improves with continued use)FlushingDizzinessHypotension / orthostatic hypotensionTachycardia (reflex)NauseaLightheadedness

Serious

Severe hypotension / syncope
Methemoglobinemia (rare, high doses)
Reflex tachycardia (may worsen angina)
Tolerance with continuous use (tachyphylaxis)
Severe headache (intolerable)

Pregnancy & lactation

Pregnancy

Use only if clearly needed; animal studies show adverse effects; nitrates used in pregnancy for hypertensive emergencies and uterine relaxation

Lactation

Excretion in breast milk unknown; use with caution during breastfeeding

Drug interactions

Sildenafil

Contraindicated

Textbook-cited

Precipitous and potentially fatal fall in blood pressure; myocardial ischemia.

Concurrent use is absolutely contraindicated

Source: KDT 7e · p950

Tadalafil

Contraindicated

Textbook-cited

Precipitous and potentially fatal fall in blood pressure; myocardial ischemia

Concurrent use is absolutely contraindicated

Source: KDT 7e · p950

Pde5 Inhibitors

Contraindicated

Database

Both increase cGMP; profound synergistic hypotension; risk of cardiovascular collapse and death

Absolute contraindication; do not use nitrates within 24h of sildenafil/vardenafil or 48h of tadalafil

Source: Kimi deep-research + Cla

Avanafil

Severe

Database

Drug interaction classified as: synergy

Source: DDInter

Nicorandil

Severe

Database

Additive hypotensive effects, potentially leading to severe hypotension, dizziness, syncope, and reflex tachycardia.

Avoid concomitant use if possible. If co-administration is necessary, monitor blood pressure closely and consider reducing the dose of one or both agents. Educate the patient about symptoms of hypotension.

Nitrous Acid

Severe

Database

Clinical effect not specified

Source: DDInter

Prilocaine

Severe

Database

Clinical effect not specified

Source: DDInter

Riociguat

Severe

Database

severe hypotension and syncope

Concurrent use is contraindicated.

Source: DDInter

Tizanidine

Severe

Database

Source: DDInter

Vardenafil

Severe

Database

Co-administration can cause profound vasodilation and potentially catastrophic hypotension.

Avoid nitroglycerin if vardenafil has been used within 24 hours.

Source: DDInter

Acetylcysteine

Moderate

Database

Acetylcysteine can potentiate the vasodilatory and hypotensive effects of nitroglycerin by increasing nitric oxide bioavailability. This can lead to significant hypotension and headache.

Monitor blood pressure closely if co-administering acetylcysteine with nitroglycerin. Consider reducing the dose of nitroglycerin or discontinuing acetylcysteine if severe hypotension occurs. This interaction is sometimes exploited therapeutically in specific cardiac conditions, but requires careful monitoring.

Alteplase

Moderate

Database

Increased hepatic alteplase clearance

Avoid concurrent IV nitroglycerin if possible

Source: Kimi deep-research + Cla