Drug reference

Isosorbide Mononitrate

Organic nitrate vasodilator · Antianginal

Also known as Isosorbide-5-mononitrate, ISMN

START

Check BP (ensure SBP >90). Verify no PDE5 inhibitor use in past 24-48h. Counsel on headache (common, usually resolves in 1 week).

TYPICAL MAX

240mg/day ER. Do not use TID/QID dosing (promotes tolerance). Maintain 10-12 hour nitrate-free interval daily.

STOP IF

SBP <90 mmHg, syncope, severe headache unresponsive to analgesia, methemoglobinemia (cyanosis, SpO2 discordance).

WATCH

Tolerance develops with continuous exposure—ensure 10-12 hour nitrate-free interval (asymmetric BID or morning-only ER). Headache is expected and usually transient. Hypotension risk increased with alcohol, other antihypertensives.

CDSCO approvedSchedule HJan AushadhiATC C01DA14

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1h · Onset 30-60 min (IR)
PEAK: 4h · Tmax ER 3.5-5 hours
t½: 5h · t½ ~5 hours
DURATION: 12h · 12-24 hours (ER)

EXCRETION

Renal as metabolites (~96%)

route + CYP

INTERACTIONS

9 major

incl. contraindicated

PREGNANCY

Limited data; use only if clearly needed. Animal studies at high doses show adverse effects.

FDA category + note

Top interactionssee all 10 →

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

Available in India

116 branded formulations and 18 fixed-dose combinations. 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 → increased cGMP → dephosphorylation of myosin light chain → vasodilation. Preferentially dilates veins > arteries, reducing preload and myocardial oxygen demand.

Indications

Prevention of angina pectorisCongestive heart failure (adjunctive, with hydralazine—BiDil)

Dosing

Adult: Angina prophylaxis (IR): 20mg BID given 7 hours apart (asymmetric dosing to prevent tolerance). Angina prophylaxis (ER): 30-60mg daily in morning, may increase to 120mg daily; max 240mg/day (ER). Heart failure (BiDil): isosorbide dinitrate 20mg + hydralazine 37.5mg TID.
Pediatric: Not established in children.
Renal adjustment: No adjustment needed.
Hepatic adjustment: No adjustment needed; metabolized in liver but well-tolerated.
Geriatric: Start at 30mg ER daily; increased sensitivity to hypotension.
Max dose: 240mg/day (ER); 40mg/day (IR BID)

Pharmacokinetics

Onset

IR: 30-60 minutes; ER: 1-2 hours

Peak effect

IR: Tmax 0.5-1 hour; ER: Tmax 3.5-5 hours

Duration

IR: 6-8 hours; ER: 12-24 hours

Half-life

~5 hours (IR and ER)

Bioavailability

~100% (no first-pass metabolism, unlike ISDN)

Protein binding

~5%

Metabolism

Hepatic denitration to isosorbide and sorbitol; glucuronidation

Excretion

~96% in urine as metabolites; ~2% unchanged

Contraindications

Hypersensitivity to nitrates
Severe hypotension (SBP <90 mmHg)
Cardiogenic shock
Sildenafil, tadalafil, or vardenafil use within 24-48 hours (PDE5 inhibitors)
Hypertrophic cardiomyopathy with outflow tract obstruction
Closed-angle glaucoma (relative)

Side effects

Common

Headache (most common—dose-dependent, often transient)DizzinessHypotensionTachycardia (reflex)Flushing

Serious

Severe hypotension / syncope
Reflex tachycardia (may worsen angina)
Methemoglobinemia (rare, high doses)
Nitrate tolerance (with continuous exposure)

Pregnancy & lactation

Pregnancy

Limited data; use only if clearly needed. Animal studies at high doses show adverse effects.

Lactation

Excretion in breast milk unknown; use with caution. No adverse effects reported in nursing infants.

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

Avanafil

Contraindicated

Database

Profound and prolonged systemic hypotension, syncope, myocardial ischemia, and even death.

Concomitant use is absolutely contraindicated. A minimum of 12 hours should elapse between the last dose of avanafil and the administration of isosorbide mononitrate.

Source: DDInter

Pde5 Inhibitors

Contraindicated

Database

Potentiation of cGMP-mediated vasodilation → severe, potentially fatal hypotension.

Absolutely contraindicated. Sildenafil/vardenafil: avoid for 24h after nitrate. Tadalafil: avoid for 48h.

Source: Kimi deep-research + Cla

Riociguat

Contraindicated

Database

Riociguat (sGC stimulator) + nitrates → excessive hypotension.

Contraindicated. Use alternative antianginal if riociguat indicated.

Source: Kimi deep-research + Cla

Vardenafil

Contraindicated

Database

Profound and prolonged systemic hypotension, syncope, myocardial ischemia, and even death.

Concomitant use is absolutely contraindicated. A minimum of 24 hours should elapse between the last dose of vardenafil and the administration of isosorbide mononitrate.

Source: DDInter

Nitrous Acid

Severe

Database

Clinical effect not specified

Source: DDInter

Prilocaine

Severe

Database

Clinical effect not specified

Source: DDInter

Tizanidine