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Isosorbide Mononitrate

*Isosorbidi mononitras*

For medical students2 min readUpdated 2026-10-10

Isosorbide mononitrate is a pharmacologically active metabolite of isosorbide dinitrate belonging to the organic nitrate group. The drug is widely used in clinical practice due to its pronounced anti-anginal properties and favorable pharmacokinetic parameters.

Trade namesImdur, Monoket, Ismo

Duration of effectUp to 12 hours and more

Drug classOrganic nitrates

Key featureRisk of tolerance development

Origin and Relation to Other Drugs

From a biochemical standpoint, Isosorbidi mononitras (specifically isosorbide-5-mononitrate) is the direct and primary active metabolite of another well-known medication, isosorbide dinitrate. This lineage determines the similarities in their pharmacological profile; however, this monometabolite possesses several significant advantages regarding systemic absorption.

Various dosage forms are used in therapeutic practice. In addition to standard options, special extended-release formulations are available that provide a smoother and more prolonged release of the active substance.

Pharmacokinetic Advantages

Compared to its precursor—isosorbide dinitrate—Isosorbidi mononitras features a favorable set of pharmacokinetic parameters:

High bioavailability: The drug is absorbed more efficiently and enters the systemic circulation.
Extended half-life ($t_{1/2}$): Provides a more stable concentration of the active component in the blood.
Prolonged anti-anginal effect: The therapeutic action lasts for 12 hours or more, which is especially pronounced when using sustained-release formulations.

Tolerance and Cross-Tolerance

The main therapeutic challenge when using this medication is the phenomenon of tolerance. Like all other organic nitrates, continuous long-term administration of Isosorbidi mononitras leads to tolerance, which is a gradual decrease in the therapeutic response.

Additionally, the drug exhibits cross-tolerance. This means that a reduced sensitivity of the body to isosorbide mononitrate automatically entails a reduced efficacy of other nitrate compounds, particularly nitroglycerin preparations.

Mnemonic

Mononitrate is 'Mono' (one active metabolite) with a long duration (up to 12 hours), but remember tolerance: nitrates lose effectiveness with continuous use!

Frequently asked questions

What is the cellular mechanism of the anti-anginal action of isosorbide mononitrate?

The mechanism involves the enzymatic release of nitric oxide (NO) from organic nitrates mediated by thiol enzymes and tissue sulfhydryl groups. At the cellular level, the reaction cascade includes:

Entry of NO into vascular smooth muscle cells (angiocytes).
Activation of cytosolic guanylyl cyclase.
Accumulation of cyclic guanosine monophosphate (cGMP).
Decrease in cytosolic calcium ion concentration.

This results in the relaxation of vascular smooth muscle cells.

What are the main clinical indications for prescribing isosorbide mononitrate?

The main indications include:

Relief and prevention of angina pectoris attacks.
Chronic heart failure as a vasodilator when ACE inhibitors cannot be used.

What adverse effects are most characteristic of isosorbide mononitrate preparations?

The most characteristic adverse effects include:

Headache and flushing.
Hypotension, including orthostatic hypotension, and syncope.
Reflex tachycardia.
Methemoglobinemia.

Overall, adverse effects are similar to those of nitroglycerin but may be less pronounced.

How can tolerance be prevented during long-term administration of isosorbide mononitrate?

To prevent tolerance, the drugs must be administered intermittently. A nitrate-free interval must be maintained between the last dose of the day and the first dose of the following day: at least 12 hours, optimally 16 hours (some sources cite 10–14 hours).

What are the absolute contraindications to taking isosorbide mononitrate?

Contraindications include:

Vasospastic angina (Prinzmetal's angina) due to the risk of increased coronary tone.
Hypertrophic obstructive cardiomyopathy (HOCM).
Severe aortic stenosis.
Concomitant use of phosphodiesterase-5 (PDE5) inhibitors due to the risk of severe systemic hypotension.

What pharmacological group does isosorbide mononitrate belong to?

The drug belongs to the organic nitrates and is the active metabolite of isosorbide dinitrate (isosorbide-5-mononitrate).

What are the main pharmacokinetic advantages over dinitrate?

It has higher bioavailability and an extended half-life ($t_{1/2}$). Consequently, the anti-anginal effect lasts up to 12 hours or longer.

Does tolerance develop to this medication?

Yes. Like other organic nitrates, long-term administration causes tolerance, and it exhibits cross-tolerance with nitroglycerin preparations.

Go deeper

Detailed analysis of mechanisms of tolerance to organic nitrates
Regimens for preventing tolerance in nitrate therapy
Comparison of pharmacokinetic parameters of short-acting and sustained-release formulations
Clinical manifestations of cross-tolerance with nitroglycerin
Metabolism of isosorbide dinitrate into its active metabolite