Isosorbide mononitrate

FDA label

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Titration Small-stature patients started at 5 mg BID: increase to at least 10 mg BID by the second or third day of therapy.

Renal No adjustment needed

Hepatic No adjustment needed

The asymmetric 7-hour-apart BID schedule is required; maintaining continuous 24-hour plasma levels produces refractory tolerance. Antianginal effect begins ~1 hour after the first dose and lasts at least 7 hours after the second; activity beyond 14 hours has not been studied. 5 mg BID is effective only on the first day.

Instructions

• Give the two daily doses 7 hours apart (asymmetric BID schedule) - this leaves a daily nitrate-free interval that limits tolerance.
• The 10 mg tablet may be split in half to give a 5 mg dose.
• No dosage adjustment is required for elderly patients or for altered hepatic or renal function.
• Not for aborting an acute anginal episode - the onset of action of oral isosorbide mononitrate is not sufficiently rapid.

Contraindications

• Concomitant phosphodiesterase inhibitors for erectile dysfunction (sildenafil, tadalafil, vardenafil) - severe hypotension, syncope or myocardial ischemia
• Concomitant soluble guanylate cyclase stimulator riociguat - hypotension

Cautions

• Severe hypotension, syncope or myocardial ischemia if combined with a PDE5 inhibitor; hypotension if combined with riociguat.
• Headache is the most frequent effect (35% at 20 mg BID) and caused 2% of trial dropouts; it lessens after the first few days.
• Nitrate tolerance - continuous 24-hour exposure produces refractory tolerance, and some tolerance still develops on the 7-hour-apart twice-daily schedule.
• Hypotension, dizziness, tachycardia, bradycardia, palpitations and pallor reported.
• Very rarely, ordinary nitrate doses have caused methemoglobinemia in otherwise normal patients.

Adverse reactions

• Headache - 35% at 20 mg, 13% at 10 mg, 17% at 5 mg (placebo 6%)
• Dizziness (4% at 20 mg)
• Nausea (3% at 20 mg)
• Fatigue
• Upper respiratory infection, cough, pain, chest pain
• Rash, pruritus, allergic reaction
• Uncommon: hypotension, hypertension, tachycardia, bradycardia, palpitations, edema, arrhythmias, myocardial infarction
• Uncommon: dry mouth, dyspepsia, vomiting, anorexia; anxiety, insomnia, nervousness, tremor, vertigo, paresthesia
• Rare: methemoglobinemia

Pregnancy Animal reproduction studies revealed no evidence of fetal harm, but there are no adequate, well-controlled studies in pregnant women - use only if clearly needed; very high rat doses in late gestation reduced birth weight and neonatal survival.

Lactation Undefined