Isodur

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Medically reviewed

Marina Burgos

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Isodur

What is Isodur? (Isosorbide-5-Mononitrate)

Isodur is a long-acting prescription medication that contains the active ingredient isosorbide-5-mononitrate. It belongs to the pharmacological class of nitrates and is primarily used for the long-term management and prevention of stable angina pectoris (chest pain) caused by Coronary Artery Disease (CAD).

Quick Facts

Property Description
Active ingredient Isosorbide-5-mononitrate
Form Extended-release (long-acting) tablet/capsule
Pharmacological class Nitrate / Vasodilator
Common use Prevention of angina pectoris
Key note It is not for treating an acute angina attack.

Overview and Function

As a nitrate, Isodur works by promoting the relaxation and widening of blood vessels, a process known as vasodilation. This action helps to improve blood flow to the heart muscle and reduces the overall strain on the heart, which is the underlying cause of angina. This function is clinically recognized for reducing the frequency and severity of angina attacks in patients requiring chronic care.

A key feature of the Isodur brand is its extended-release formulation. This design ensures the active ingredient is released slowly and consistently over many hours, providing a steady, preventative effect throughout the day. This sustained action is crucial for maintaining continuous vessel relaxation and minimizing the risk of chest pain episodes.

It is essential to note that, due to its long-acting profile, Isodur is intended solely for prevention and will not provide rapid relief during an angina attack that has already started. Other, short-acting nitrates are prescribed specifically for immediate symptomatic relief.

Regulatory References

  1. Isosorbide: MedlinePlus Drug Information
  2. NIH/NLM Reference

What side effects are possible with Isodur?

Possible Side Effects and Safety Information

The safety profile of Isodur (isosorbide-5-mononitrate) is officially documented by regulatory authorities, with adverse reactions generally categorized by frequency and the body system affected. These effects are often related to the medicine's vasodilating action.


Frequency-Classified Adverse Reactions

The most frequent adverse reaction is headache, which is officially classified as Very Common and can affect more than 1 in 10 patients. This effect is often most noticeable at the initiation of treatment and is documented to decrease in incidence after the first few days of therapy.

Common reactions, affecting up to 1 in 10 patients, include effects on the Nervous System (e.g., dizziness, light-headedness) and Vascular System (e.g., hypotension, flushing). Nausea and fatigue are also listed as common effects.

Serious Safety Considerations

The official label documents potential Serious Adverse Reactions, including severe hypotension (low blood pressure), which may be accompanied by an increase in angina pectorus, and syncope (fainting). Use is contraindicated in patients with a known hypersensitivity to any nitrate/nitrite.

Safety constraints also require caution in certain populations, as older adults may be at greater risk for some side effects, especially severe low blood pressure. Furthermore, safety and effectiveness have not been established in pediatric patients, and the drug is not recommended for the treatment of acute cardiac events like acute myocardial infarction.

Overdose and Emergency Response

A severe overdose of Isodur (isosorbide-5-mononitrate) is associated with exaggerated pharmacological effects that necessitate immediate medical attention. The official regulatory documents state that an overdose may manifest as marked hypotension (low blood pressure) and compensatory reflex tachycardia (rapid heart rate). These circulatory effects can progress to syncope or, in severe cases, circulatory failure (shock).

Neurological manifestations are also documented, including severe, throbbing headache, confusion, dizziness, and visual disturbances. Extremely high exposure may lead to seizures or signs of raised intracranial pressure. A specific, serious outcome noted in regulatory labeling is methaemoglobinaemia, a condition where oxygen transport is compromised, which requires specific intervention.

It is mandatory to seek immediate medical attention or contact a Poison Control center if an overdose is suspected. Management procedures described in official labeling include steps to correct severe hypotension, such as intravascular volume expansion (intravenous fluids) and passive leg elevation. Caution is required when performing fluid expansion in patients with congestive heart failure or renal disease. Following initial intervention, regulatory guidelines mandate that the patient be observed for at least 12 hours.

Therapeutic Uses of Isodur

Quick Facts

  • Primary Therapeutic Domain: Supports the management of chest pain (angina).
  • Indication: Used for the prevention of anginal episodes related to coronary artery disease.
  • Therapeutic Action: May contribute to an improved patient experience by reducing the occurrence of episodes.

Isodur (isosorbide mononitrate) is a therapeutic agent prescribed for the long-term management of angina pectoris, a condition marked by chest discomfort resulting from coronary artery disease. The agent is used to reduce the frequency and severity of anginal episodes, potentially leading to an overall improved quality of life for the patient.

Its function involves processes that contribute to the relaxation of vascular smooth muscle, which supports enhanced blood flow and oxygen supply to the heart muscle. This action helps to manage the underlying factors that contribute to the recurrence of anginal pain. It is important to note that this formulation is utilized as a preventative measure and is not intended for the rapid relief of an acute, ongoing episode of chest pain.

Eligibility and Restrictions for Use

Isodur (isosorbide-5-mononitrate) eligibility is strictly defined by regulatory authorities to ensure patient safety and adherence to labeled conditions. The medicine is contraindicated and must not be used by populations with specific severe conditions, including:

  • Severe hypotension (very low blood pressure) or acute circulatory failure (shock).
  • Obstructive heart conditions such as hypertrophic obstructive cardiomyopathy (HOCM) or cardiac tamponade.
  • Concurrent use of Phosphodiesterase type-5 (PDE5) inhibitors (like sildenafil) or riociguat.
  • Severe anaemia or conditions associated with raised intracranial pressure.

Restrictions and Limitations

Use is restricted or conditional in other populations. The medicine is not established and not recommended for the pediatric population. Use during pregnancy or lactation is permitted on a conditional basis only, requiring a determination that the benefits of treatment outweigh the potential hazards, as safety is not established. Caution and special care are necessary for patients with severe renal impairment or severe hepatic impairment. Isodur is otherwise typically used by adults and the elderly without routine age-related dose adjustments.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Isodur (isosorbide-5-mononitrate) has documented interaction patterns based primarily on pharmacodynamic synergism—additive effects that can lead to severe lowering of blood pressure (hypotension).

Contraindicated Combinations

Co-administration with specific medicinal products is strictly prohibited according to regulatory labeling due to the risk of dangerous, life-threatening hypotension and syncope.

Substance Class Specific Medicines Interaction Restriction
PDE5 Inhibitors Sildenafil, Tadalafil, Vardenafil, Avanafil Contraindicated
sGC Stimulators Riociguat Contraindicated

Pharmacodynamic Interactions

Combining Isodur with other agents that lower blood pressure may result in additive hypotensive effects or marked symptomatic orthostatic hypotension. This includes other classes of antihypertensive drugs, such as Beta-blockers and Calcium Channel Blockers. The consumption of alcohol (ethanol) also exhibits an additive vasodilating effect, which increases the risk of enhanced low blood pressure.

Timing and Separation Rules

To mitigate the interaction risk with prohibited substances, specific administration timing rules are mandated. Nitrate administration must be separated by at least 48 hours following the last dose of tadalafil and by at least 24 hours following sildenafil, vardenafil, or avanafil, as per regulatory guidance.

Pharmacokinetic Notes

The official interaction profile does not detail clinically relevant restrictions based on Cytochrome P450 enzyme or drug transporter inhibition/induction.

Mechanism of Action

Isodur, or isosorbide-5-mononitrate, functions through a cascade that fundamentally alters vascular tone and systemic hemodynamics. Its mechanism centers on acting as a prodrug to directly engage the Nitric Oxide (NO) signaling pathway within vascular smooth muscle.

Molecular Activation and Cellular Relaxation

The drug is converted into the active NO molecule, which subsequently targets the enzyme soluble guanylyl cyclase (sGC). Activation of sGC rapidly increases the concentration of cyclic GMP (cGMP), a secondary messenger that initiates the sequence of molecular events necessary to reduce intracellular calcium and cause vasodilation.

Hemodynamic Modulation and Cardiac Workload

The resulting vasodilation is primarily directed toward the venous capacitance vessels. This action significantly increases the pooling of blood in the periphery, thereby reducing the volume and pressure of blood returning to the heart (the cardiac preload). This physiological adjustment effectively minimizes ventricular wall tension, which is the core mechanism that lowers the myocardial oxygen demand. The combined mechanistic effects of reduced oxygen demand and optimized supply constitute the primary physiological alteration.

Intrinsic Mechanistic Limitation (Tolerance)

Sustained, continuous drug exposure can lead to nitrate tolerance, a phenomenon where the biological pathway becomes less responsive. This constraint involves both the potential impairment of the bioactivation machinery (reducing NO release) and the functional override by counter-regulatory neurohormonal systems that promote vasoconstriction, weakening the drug's sustained vasodilatory effect.

Dosage and Administration Information

How to Use Isodur

Isodur (isosorbide-5-mononitrate extended-release) is administered exclusively through the oral route. The medication is provided as an extended-release tablet or capsule, which follows a specific protocol for its use.

Administration Scope

Feature Detail
Dosing Schedule Standard Starting Dose: 30 mg or 60 mg once daily. Maximum Dose: Up to 120 mg once daily.
Timing The dose is taken once daily in the morning (on arising), and may be taken with or without food.
Handling The extended-release tablet or capsule must be swallowed whole with fluid and must not be crushed, chewed, or divided.
Age-Group Rule Pediatric Population: Not recommended for use, as safety and efficacy are not established.
Discontinuation Treatment should not be stopped suddenly; dosage and frequency must be tapered gradually before discontinuation.

Official Use Pattern

Classification Detail
Frequency Pattern Once daily (q24h).
Use-Context Constraint The morning dose is specifically scheduled to provide a necessary drug-free interval overnight, which is required to prevent the development of pharmacological tolerance over long-term use.

Resulting Procedural Structure

Official steps for use:

  • Swallow the full dose of the extended-release tablet or capsule whole with a sufficient amount of fluid.
  • Take the required dose once daily in the morning upon waking.
  • If a dose is missed, take it as soon as remembered unless it is nearly time for the next dose; double dosing is not instructed.

Connection to the Official Use Protocol

The official administration guidelines establish a standardized protocol centered on a single daily oral dose taken in the morning to manage the drug’s long-term effect. This protocol strictly requires the medication to be swallowed intact, preserving the functional integrity of the extended-release formulation. These instructions also define the mandatory procedure for stopping the medication, requiring a gradual reduction in dosage over time.

Recent Clinical Evidence

Overview of Research Evidence for Isodur

Evidence for Use in Preventing Chronic Stable Angina

Isodur was evaluated in research exploring the long-term management of chest pain (angina) that arises from coronary artery disease. Evidence primarily comes from Randomized Controlled Trials (RCTs) conducted in adult patients. These short-term studies examined outcomes related to functional capacity, such as time to onset of chest pain during controlled exercise, and assessed the frequency of recorded weekly angina attacks compared to placebo. Findings reported how symptoms evolved, but research describes that the antianginal pattern observed in studies may change over time due to the potential for tolerance.

Long-Term Data and Secondary Use

Research has explored how the antianginal pattern is sustained over extended periods through observational settings, but controlled trials often have follow-up durations that were limited to a few months, meaning long-term effects are not fully established. Isodur was also studied as a supplemental agent for managing conditions such as esophageal variceal bleeding. Findings from systematic reviews in this area were mixed, and while certain patterns related to reduced bleeding risk were observed in some studies, the certainty remains low compared to the evidence for angina prevention.

Gaps and Limitations in Research

The major efficacy studies focused on adult patients, often including those receiving concurrent antianginal therapy. However, data for certain subgroups, such as very young or very elderly patients, remain insufficient, and results apply only to the populations studied. A critical research limitation is the lack of long-term outcomes related to major clinical events, such as reducing heart attack or death. Comparative evidence is lacking for many subgroups, and the need for additional, larger randomized studies remains to confirm the observations.

Frequently Asked Questions (FAQ)

Common questions about Isodur (FAQ)

Q: Can Isodur be taken at the same time as common blood pressure medicines?

A: Official product information indicates that taking Isodur with other medicines that lower blood pressure, such as antihypertensive drugs, may cause an additive hypotensive effect. This means the combined effect could lower blood pressure further than expected, which is noted in regulatory documents.

Q: Why do some people feel dizzy when standing up after taking Isodur?

A: Light-headedness or dizziness, especially when standing up quickly after sitting or lying down, is a known effect. This is related to postural or orthostatic hypotension, which is a drop in blood pressure upon changing position. This effect is documented in the official safety information.

Q: What is the difference between Isodur and Isosorbide Mononitrate?

A: Isosorbide Mononitrate is the active chemical ingredient (generic name) of the drug. Isodur is one of the brand names under which this active ingredient is sold. The therapeutic effects of the medicine come directly from the action of isosorbide mononitrate.

Q: Does Isodur affect lab results like blood tests?

A: Regulatory documents state that nitrates and nitrites, the class of drugs Isodur belongs to, may interfere with certain laboratory tests. Specifically, they may interact with the chemical reaction used to determine serum cholesterol, potentially leading to falsely low cholesterol readings.

Q: Are there different brand names for the same active ingredient as Isodur?

A: Yes, the active ingredient in Isodur is isosorbide mononitrate, which is the generic name for the compound. This ingredient is also available under several other brand names, such as Imdur and Monoket.

Q: Can Isodur be taken with or without food?

A: The extended-release formulation of Isodur may be taken with or without food. Official information indicates that the absorption of the drug is generally not significantly affected by whether or not you eat when you take your dose.

Q: Is Isodur a long-term treatment, or is it used short-term?

A: Isodur is indicated for the prevention of angina pectoris (chest pain) caused by coronary artery disease. It is typically prescribed as a daily medication intended for long-term use to manage and prevent symptoms over time.

Q: Is Isodur the same type of medicine as nitroglycerin?

A: Both Isodur and nitroglycerin belong to the same class of medicines known as nitrate vasodilators. However, they have different uses: Isodur is formulated for the long-term prevention of chest pain, while nitroglycerin is used for the immediate relief of an acute angina attack.

Q: How long does it usually take for the effects of Isodur to start?

A: The regulatory documents emphasize that the onset of action for the oral tablet is not rapid enough to be used to stop or abort a sudden, acute episode of chest pain. It is formulated to be a maintenance medication, not a quick-relief treatment.

Q: What are the signs of taking too much Isodur?

A: Signs of taking too much are typically related to the medication’s strong vasodilating effects. Symptoms listed in regulatory information may include a severe, persistent throbbing headache, confusion, dizziness, palpitations, and syncope (fainting). Other reported effects include visual disturbances, severe nausea, or vomiting.

Q: Can people with kidney problems use Isodur?

A: Official information indicates that a cautious approach is taken when considering use in patients who have severe kidney (renal) or liver (hepatic) disease. It is noted that a dosage adjustment, decided by a healthcare professional, may be necessary for those with kidney or liver impairment.

Q: How is Isodur different from Isosorbide Dinitrate?

A: Isosorbide Dinitrate (ISDN) is considered a prodrug, which means the body must first convert it into isosorbide mononitrate (the active ingredient in Isodur) before it works. Isosorbide mononitrate typically has a longer duration of action and a more predictable effect than the dinitrate form.

Q: What kind of studies have been done on the long-term use of Isodur?

A: Research has examined how the medication maintains its antianginal effect over time. This includes studies that observed functional capacity outcomes, such as exercise performance, over controlled periods spanning several weeks to assess the long-term pattern of benefit.

Q: Can people with low blood pressure use Isodur?

A: Official product labeling states that Isodur is contra-indicated, meaning it should not be used, in patients who have marked low blood pressure (systolic blood pressure of 90 mmHg or lower). It is also contra-indicated in cases of acute circulatory failure or shock.

Q: Is it safe to take supplements, like vitamins, with Isodur?

A: Regulatory warnings state there is generally not enough established information to confirm the safety of taking complementary medicines, herbal remedies, or general supplements alongside this medication. Because of this gap in testing, potential interactions are unknown.

Q: Is there an interaction warning for Isodur and herbal products?

A: Official documentation provides an explicit warning that there is not enough established information to confirm the safety of taking herbal products with Isodur. This means any potential interactions are not fully known or tested.

Q: Does Isodur interact with certain anti-depressant medications?

A: Some regulatory information notes that certain types of antidepressant medications, such as tricyclic antidepressants, may interact with Isodur. This interaction is described as potentially having an additive effect in lowering blood pressure.

Q: What is the shelf life of Isodur tablets?

A: The official shelf life (expiration date) for the specific product is printed on the medication's outer packaging. Depending on the formulation, some extended-release products containing isosorbide mononitrate have been documented to have a shelf life of up to 36 months when stored correctly.

Q: What research is available on Isodur's use in younger adults?

A: Research has primarily focused on adult patients. While safety and effectiveness have not been fully established in children or younger pediatric patients, certain pharmacokinetic studies have been conducted to understand the drug levels and absorption in subjects including adolescents.

Q: Isodur only for people who have already had a heart problem?

A: The regulatory indication for this drug is the prevention of chest pain (angina pectoris) that is caused by coronary artery disease. It is prescribed for this specific disease state.

Q: Do regulatory agencies classify Isodur as a drug with a high potential for dependence?

A: Regulatory documents note that in industrial settings involving continuous exposure to high doses of organic nitrates, physical dependence has been observed. However, the official labeling states that the significance of these observations regarding the routine, clinical use of the oral medication is not established.

Q: What is the typical duration of action for an Isodur extended-release tablet?

A: The extended-release formulation is designed to provide a sustained effect. The antianginal effect of the extended-release tablet is officially documented as lasting for at least 12 hours.

Q: Does Isodur affect sleep?

A: Official safety information lists disturbed sleep as a possible side effect of the medication. This effect has been reported in clinical trials, although it is not classified among the most common adverse reactions.

Q: Are the side effects of Isodur different for men versus women?

A: While there is no official statement indicating a difference in side effect incidence between sexes, pharmacokinetic research has indicated that plasma concentrations of the drug may be higher in female subjects compared to male subjects. This difference is mainly attributed to differences in body weight.

How should Isodur be stored and disposed of?

Storage and Disposal of Isodur (Isosorbide Mononitrate)

Storage of Isodur tablets must strictly follow regulatory guidance to ensure product stability and safety.

Official Storage Requirements

Condition Regulatory Requirement
Temperature Store at Controlled Room Temperature, typically 15 to 30 C (59 to 86 F). Do not allow the product to freeze.
Protection Keep the medication protected from light and excessive moisture.
Container Dispense in a light-resistant, tightly closed container.
Child Safety Must be kept out of the sight and reach of children.

Disposal

Expired or unused isosorbide mononitrate must be handled according to local, state, and national regulations. The medicine should not be disposed of in household trash or poured down drains or sewers to prevent environmental contamination. Patients should consult a healthcare professional or local waste disposal service for proper discarding instructions.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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