Imdur (isosorbide mononitrate) is a long-acting nitrate vasodilator specifically formulated for the prophylactic management of angina pectoris. It is indicated for patients with stable coronary artery disease to reduce the frequency and severity of angina attacks. By relaxing vascular smooth muscle, it decreases preload and afterload, thereby reducing myocardial oxygen demand. This medication is a cornerstone in the pharmacological management of chronic stable angina, offering predictable 12-hour coverage with a convenient once- or twice-daily dosing regimen for many patients.

Features

• Active ingredient: Isosorbide mononitrate
• Pharmacologic class: Organic nitrate vasodilator
• Available in extended-release tablet formulations (e.g., 30 mg, 60 mg, 120 mg)
• Provides sustained nitrate activity for up to 12 hours
• Demonstrated efficacy in clinical trials for angina prophylaxis
• Standardized manufacturing process ensuring consistent dosing

Benefits

• Significantly reduces the frequency of angina attacks
• Increases exercise tolerance and functional capacity in patients with angina
• Decreases nitroglycerin rescue medication requirements
• Provides predictable, extended hemodynamic effects for stable prophylaxis
• Convenient dosing schedule supports medication adherence
• Well-established safety profile with extensive clinical experience

Common use

Imdur is primarily prescribed for the prophylaxis of angina pectoris in patients with documented coronary artery disease. It is not intended for the acute relief of angina attacks, for which sublingual nitroglycerin remains the standard treatment. The medication is typically used as part of a comprehensive cardiovascular management plan that may include beta-blockers, calcium channel blockers, antiplatelet agents, and lifestyle modifications. Clinical use is generally reserved for patients with confirmed ischemic heart disease who experience recurrent angina despite optimal medical management.

Dosage and direction

The recommended initial dosage for most patients is 30 mg or 60 mg once daily, typically taken in the morning. Dosage may be titrated upward based on therapeutic response and tolerance, with maximum recommended doses generally not exceeding 120 mg once daily. Some patients may require twice-daily dosing (every 12 hours) to maintain adequate antianginal coverage throughout the day. Tablets should be swallowed whole with a glass of water and not crushed or chewed. To minimize the development of tolerance, a daily nitrate-free interval of 10-14 hours is recommended, typically achieved by dosing in the morning only.

Precautions

Patients should be advised that Imdur may cause hypotension, particularly upon initiation or dosage increase. Caution is warranted in patients with hypovolemia, hypotension, or hypertrophic cardiomyopathy. Headache is common initially but typically diminishes with continued therapy. Alcohol consumption may potentiate hypotensive effects. Abrupt discontinuation may precipitate rebound angina. Patients should be monitored for signs of inadequate angina control or worsening ischemic symptoms. Use with caution in patients with severe hepatic or renal impairment, though dosage adjustment may not be necessary.

Contraindications

Imdur is contraindicated in patients with known hypersensitivity to organic nitrates. It must not be used concurrently with phosphodiesterase-5 inhibitors (sildenafil, tadalafil, vardenafil) due to the risk of profound hypotension. Additional contraindications include severe anemia, increased intracranial pressure, and circulatory failure associated with myocardial infarction. The medication is not indicated for use in the acute treatment of angina attacks or in patients with cardiogenic shock.

Possible side effects

The most frequently reported adverse reaction is headache (occurring in >30% of patients), which is often dose-related and typically diminishes with continued therapy. Other common side effects include dizziness (4-8%), hypotension (2-5%), and nausea (2-4%). Less frequently, patients may experience flushing, palpitations, or syncope. Cutaneous vasodilation with flushing may occur. Serious adverse effects are rare but may include severe hypotension, reflex tachycardia, or methemoglobinemia (particularly with overdose).

Drug interaction

Concomitant use with phosphodiesterase-5 inhibitors is absolutely contraindicated due to risk of life-threatening hypotension. Additive hypotensive effects may occur with other vasodilators, antihypertensives, calcium channel blockers, beta-blockers, alcohol, or tricyclic antidepressants. Aspirin may increase nitrate serum concentrations. Heparin’s anticoagulant effect may be decreased. Ergot alkaloids may antagonize the vasodilatory effects. Monoamine oxidase inhibitors may potentiate hypotensive effects.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next scheduled dose. In that case, the missed dose should be skipped and the regular dosing schedule resumed. Patients should not double the dose to make up for a missed administration. Consistent dosing is important for maintaining therapeutic effect, but occasional missed doses are unlikely to cause significant clinical deterioration in stable patients.

Overdose

Nitrate overdose manifests primarily as vasodilation with severe hypotension, syncope, dizziness, palpitations, visual disturbances, and flushing. Methemoglobinemia may occur with massive overdose. Management includes elevation of legs, administration of intravenous fluids, and supportive care. Methylene blue may be indicated for methemoglobinemia. Hemodialysis is not effective for nitrate removal. Hypotension may be refractory to catecholamines, and alpha-adrenergic agonists may be required.

Storage

Store at controlled room temperature (20-25°C/68-77°F) in the original container with the lid tightly closed. Protect from moisture and light. Keep out of reach of children and pets. Do not transfer to other containers. Discard any medication that has expired or shows signs of deterioration. Do not flush medications down the toilet or pour down the drain unless specifically instructed to do so.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Individual patient responses to medication may vary. Treatment decisions should be made in consultation with a qualified healthcare professional based on individual patient characteristics and clinical circumstances. The prescribing physician should be familiar with complete prescribing information and current clinical guidelines for angina management.

Reviews

Clinical studies demonstrate that approximately 70-80% of patients experience significant reduction in angina frequency with Imdur therapy. The extended-release formulation is generally well-tolerated, with most adverse effects being mild to moderate in severity. Headache, while common initially, typically resolves within the first week of therapy in most patients. Patient satisfaction surveys indicate improved quality of life measures related to reduced angina symptoms and increased physical activity tolerance. Long-term follow-up data support maintained efficacy with appropriate dosing strategies that include nitrate-free intervals to prevent tolerance development.