Imdur (isosorbide mononitrate) is a long-acting nitrate vasodilator prescribed for the prophylactic management of angina pectoris. It works by relaxing vascular smooth muscle, predominantly in the venous circulation, which reduces preload and myocardial oxygen demand. This medication is indicated for the prevention of angina attacks and is not intended for the acute termination of an ongoing anginal episode. Proper dosing and adherence are critical for achieving optimal therapeutic outcomes and minimizing the potential for nitrate tolerance.

Features

• Active ingredient: Isosorbide mononitrate
• Available in extended-release tablet formulations (e.g., 30 mg, 60 mg, 120 mg)
• Designed for once-daily dosing to support patient compliance
• Provides sustained nitrate activity for prolonged angina prophylaxis
• Manufactured under strict pharmaceutical quality control standards

Benefits

• Significantly reduces the frequency and severity of angina attacks
• Decreases myocardial oxygen demand through preload reduction
• Supports improved exercise tolerance and functional capacity in patients with chronic stable angina
• Convenient once-daily dosing regimen enhances adherence compared to shorter-acting nitrates
• Contributes to an overall improved quality of life by reducing angina-related limitations

Common use

Imdur is primarily used for the prophylactic management of chronic stable angina pectoris in patients with documented coronary artery disease. It is not indicated for use in the acute treatment of anginal attacks, for which sublingual nitrates remain the standard of care. It may be used as monotherapy or as part of a comprehensive anti-anginal regimen alongside beta-blockers, calcium channel blockers, or other cardiovascular agents, depending on individual patient characteristics and comorbidities.

Dosage and direction

The typical starting dose for Imdur is 30 mg or 60 mg administered orally once daily upon awakening. Dosage may be titrated upward based on therapeutic response and tolerability, with a maximum recommended dose of 240 mg once daily. Tablets should be swallowed whole and must not be crushed, chewed, or split. To minimize the risk of nitrate tolerance, a daily nitrate-free interval of 10–14 hours is recommended, which is naturally provided by the once-daily morning dosing schedule. Dosage adjustments may be necessary in patients with hepatic impairment.

Precautions

Patients should be advised that Imdur may cause hypotension, particularly upon initiation or dose escalation. Caution is advised in patients with volume depletion or pre-existing hypotension. Use with care in patients with hypertrophic cardiomyopathy, as nitrate-induced reduction in preload may exacerbate left ventricular outflow obstruction. Headache is a common initial side effect that often diminishes with continued therapy; abrupt withdrawal should be avoided to prevent rebound angina. Alcohol consumption may potentiate hypotensive effects.

Contraindications

Imdur is contraindicated in patients with known hypersensitivity to nitrates or any component of the formulation. It is absolutely contraindicated in patients who have taken phosphodiesterase inhibitors (e.g., sildenafil, tadalafil, vardenafil) within the preceding 24–48 hours due to the risk of profound hypotension. Additional contraindications include severe anemia, increased intracranial pressure, and circulatory failure associated with marked hypotension (shock).

Possible side effects

The most frequently reported side effect is headache (often pulsating and dose-related), which occurs in approximately 30% of patients. Other common adverse reactions include dizziness, hypotension, nausea, and flushing. Less frequently reported effects include tachycardia, syncope, and cutaneous vasodilation. These effects are typically dose-dependent and may diminish with continued therapy. Serious adverse reactions are rare but may include severe hypotension, reflex tachycardia, or methemoglobinemia (particularly at high doses or in patients with predisposing conditions).

Drug interaction

Concomitant use with phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil) is contraindicated due to risk of severe hypotension. Additive hypotensive effects may occur with other vasodilators, antihypertensive agents, calcium channel blockers, beta-blockers, alcohol, or tricyclic antidepressants. Aspirin may increase nitrate serum concentrations. Heparin’s anticoagulant effect may be reduced when administered with intravenous nitroglycerin (relevance to oral nitrates is uncertain but should be monitored).

Missed dose

If a dose is missed, it should be taken as soon as remembered on the same day. However, if it is near the time for the next scheduled dose, the missed dose should be skipped and the regular dosing schedule resumed. Patients should not double the dose to make up for a missed one. Maintaining the prescribed nitrate-free interval is important to prevent tolerance development.

Overdose

Nitrate overdose manifests primarily as vasodilation leading to severe hypotension, syncope, tachycardia, flushing, headache, dizziness, and nausea. Methemoglobinemia may occur with massive overdose. Management includes placing the patient in a supine position with legs elevated to optimize venous return. Supportive care, including intravenous fluids and vasopressors (e.g., norepinephrine) may be necessary. Methylene blue may be administered for clinically significant methemoglobinemia. Hemodialysis is not effective for nitrate removal.

Storage

Store Imdur tablets at controlled room temperature (20–25°C or 68–77°F), in a tightly closed container, protected from light and moisture. Keep out of reach of children and pets. Do not use beyond the expiration date printed on the packaging. Do not transfer tablets to alternative containers that lack proper light protection.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Imdur is a prescription medication that should be used only under the supervision of a qualified healthcare professional. Dosage, indications, and monitoring requirements must be individualized based on the patient’s clinical status. Patients should consult their physician for diagnosis, treatment decisions, and any questions regarding their medication regimen.

Reviews

Clinical trials and post-marketing surveillance have demonstrated that Imdur is effective in reducing angina frequency and improving exercise tolerance in the majority of patients with chronic stable angina. Many clinicians appreciate the once-daily dosing for its positive impact on adherence compared to multiple-daily-dose nitrate regimens. The development of tolerance remains a pharmacological consideration, though the once-daily regimen with a built-in nitrate-low interval helps mitigate this effect. Patient-reported outcomes often indicate improved quality of life due to reduced angina burden, though initial headaches can be a limiting factor for some individuals.