Ismo-20

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Medically reviewed

Laura Arias

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 Ismo-20

Quick Facts

Property Description
Active Ingredient Isosorbide Mononitrate
Form Oral tablet
Pharmacological Class Organic Nitrate, Vasodilator
General Purpose Prevention of Angina Pectoris (chest pain)
Origin Synthetic compound

What Type of Medicine is Ismo-20?

Ismo-20 is a prescription-only medicine containing the active ingredient Isosorbide Mononitrate, which belongs to the pharmacological class of Organic Nitrates and functions as a Vasodilator. It is categorized as an Antianginal Agent, designed to manage conditions associated with reduced blood flow to the heart muscle. The active compound is a synthetic chemical entity recognized for its essential role in cardiovascular care needs globally.


Composition and Unique Form of Isosorbide Mononitrate

The product is a single-ingredient preparation containing only Isosorbide Mononitrate, formulated for oral administration as an immediate-release tablet. This compound is distinguished by its high bioavailability, meaning a large percentage of the active ingredient is absorbed directly into the bloodstream without significant initial metabolic breakdown. This structural advantage ensures a more consistent plasma concentration for reliable long-term therapeutic effect.


General Purpose as a Prophylactic Antianginal Agent

The general purpose of Ismo-20 is the prophylaxis (prevention) of angina pectoris, or chest pain, typically caused by limited blood flow to the heart. A typical use scenario involves its prescribed administration to maintain stability and prevent the recurrence of chest discomfort. It achieves this by causing vascular smooth muscle relaxation, which widens the veins and arteries. This action reduces the workload on the heart, decreasing its demand for oxygen, thereby preventing the pain associated with restricted blood supply. It is used exclusively to maintain long-term relief and stability in adult patients.

What side effects are possible with Ismo-20?

Possible Side Effects and Safety Information

Ismo-20 (isosorbide mononitrate) is associated with adverse reactions primarily related to its vasodilatory effects. The frequency and type of side effects are documented in official regulatory labeling.

Frequency-Classified Adverse Reactions

The most common adverse reactions reported are:

  • Very Common: Headache. This side effect is often observed at the start of treatment and usually diminishes after a few days of continued use.
  • Common: Dizziness, hypotension (low blood pressure), and nausea.
  • Uncommon: Vomiting, transient hypoxemia, and allergic skin reactions like a rash.
  • Rare: Severe dermatological reactions, such as Exfoliative Dermatitis.

System-Organ Classes and Serious Reactions

The most frequently affected body systems are the Nervous System (e.g., headache, dizziness) and the Vascular System (e.g., hypotension). Serious, though rare, adverse reactions include severe hypotension or circulatory collapse (shock), sometimes accompanied by syncope (fainting). A theoretical concern for Methaemoglobin formation also exists.

Safety Limitations and Restrictions

This medication must not be used in certain situations due to the risk of severe, life-threatening hypotension or circulatory collapse. These absolute contraindications include:

  1. Concomitant use with Phosphodiesterase Type 5 Inhibitors (e.g., sildenafil, tadalafil).
  2. Acute circulatory failure (shock, vascular collapse).
  3. Marked hypotension (e.g., systolic blood pressure le 90 mmHg).

Population-Specific Notes

The safety and effectiveness of Ismo-20 have not been established for use in the pediatric population, during pregnancy, or lactation. Caution is advised for patients with severe hepatic or renal impairment.

Overdose and Emergency Response

Overdose and When to Seek Help

Overdose with Isosorbide Mononitrate (Ismo-20) is officially documented in regulatory labeling as resulting primarily from excessive vasodilation, leading to a state of Severe Hemodynamic Compromise.

The documented clinical manifestations of an overdose often include severe hypotension (a dangerous drop in blood pressure), a persistent throbbing headache, flushing, tachycardia (rapid heart rate), dizziness, and syncope (fainting). Severe or life-threatening outcomes officially described in prescribing information include circulatory collapse, shock, and the possibility of Methemoglobinemia, which affects the blood's oxygen-carrying capacity.

Emergency Actions and Management

Government regulatory guidance mandates that patients or caregivers seek immediate medical attention and contact emergency services immediately if an overdose is suspected or confirmed.

Treatment procedures documented in official labels are symptomatic and supportive. While no specific antidote is known for the primary vasodilator effects, the label specifies that Methylene blue is required for the management of confirmed Methemoglobinemia. Intensive monitoring of cardiac and circulatory function is required, and measures such as gastric lavage or activated charcoal may be considered depending on the timing of ingestion. Hospital monitoring may be required to observe the patient's hemodynamic status.

Therapeutic Uses of Ismo-20

What Ismo-20 Treats: Main Uses and Benefits

Ismo-20, containing isosorbide mononitrate, is generally applied across domains where additional symptomatic support is needed for certain cardiovascular conditions characterized by periods of heightened symptoms.

Specifically, the medication is commonly used to help with the prophylaxis (prevention) and treatment of angina pectoris, a condition involving episodic or fluctuating manifestations (chest pain). It also serves as adjunctive therapy in congestive heart failure (CHF) and is relevant in contexts involving heightened systemic burden. The use of this medication may assist with maintaining functional stability, thereby contributing to improved comfort during periods of heightened symptoms.

The medication is relevant for easing symptoms that become more disruptive during flare-ups. This supportive relief provides supportive relief when symptoms interfere with routine activities.

“This medicine is commonly used in settings marked by temporary physiological imbalance and during phases when symptoms become more noticeable.”

This medication is commonly used across conditions presenting with acute episodes and is not applied in addressing an acute or ongoing attack of chest pain.

Quick Fact: Helps address Symptoms related to physical discomfort

Regulatory References

  1. UK Summary of Product Characteristics (SmPC) for ISMO 20

Eligibility and Restrictions for Use

Official Eligibility Profile

This section outlines the patient populations and conditions defining eligibility for Ismo-20, based strictly on authoritative regulatory documentation.

Population Status Official Regulatory Rule
Absolute Contraindication Ismo-20 must not be used by patients with a known hypersensitivity to nitrates or concurrent use of Phosphodiesterase Type 5 (PDE-5) Inhibitors (e.g., sildenafil, tadalafil) or riociguat. It is also contraindicated in patients with acute circulatory failure or shock.
Not Recommended The medicine is not recommended for managing an acute anginal attack, acute myocardial infarction, or acute congestive heart failure, as its onset of action is not rapid enough for immediate symptomatic relief.
Age-Related Eligibility Use is established in adults. Safety and effectiveness have not been established in the pediatric population (children). Older adults require caution due to increased susceptibility to severe hypotension.
Conditional Use Caution is required in patients who are hypotensive, volume depleted, or have conditions such as hypertrophic cardiomyopathy. Eligibility is generally unaffected by renal or hepatic impairment, as drug clearance is documented as similar to healthy individuals.
Pregnancy/Lactation Safety in human pregnancy has not been established; use is only if the potential benefit outweighs the potential risk. It is not known if the drug is excreted in human milk; use during lactation requires caution.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Ismo-20 (Isosorbide Mononitrate) has specific officially documented interaction patterns that govern its co-administration with certain substances and medications.


Contraindicated Combinations

Co-administration with the following drug classes is strictly prohibited by regulatory labeling due to the risk of severe, life-threatening hypotension, syncope, or myocardial ischemia:

  • Phosphodiesterase-5 (PDE5) Inhibitors: This includes medicines such as sildenafil, tadalafil, vardenafil, and avanafil.
  • Soluble Guanylate Cyclase (sGC) Stimulators: This includes medicines such as riociguat.

Pharmacodynamic and Exposure Interactions

Ismo-20 interacts with other substances primarily through additive effects on blood pressure and, in specific cases, through modification of a co-administered drug's concentration.

  • Other Blood Pressure Lowering Agents: Concurrent use with vasodilators, beta-blockers, and calcium channel blockers may result in additive hypotensive effects. Combination with calcium channel blockers has been associated with reports of marked symptomatic orthostatic hypotension.
  • Alcohol: Consumption of alcohol exhibits an additive hypotensive effect and may potentiate the risk of severe postural hypotension.
  • Dihydroergotamine: Concomitant use may increase the blood level of dihydroergotamine, which can increase its hypertensive effect.

Interaction-Related Restrictions

Regulatory documents classify the combination with PDE5 inhibitors and sGC stimulators as an absolute contraindication, establishing a fundamental restriction on use. No mandatory administration time separation rules are defined in the labeling; restrictions are focused entirely on prohibiting co-administration of strictly incompatible agents.

Mechanism of Action

Nitric Oxide Signaling and Vascular Tone Modulation

This mechanism begins at the molecular level, where Ismo-20 (Isosorbide Mononitrate) acts as a Nitric Oxide (NO) Donor . The released NO activates the enzyme Soluble Guanylyl Cyclase (sGC), triggering the production of the critical signaling molecule extbfcGMP. This cascade ultimately relaxes the vascular smooth muscle, a cellular action that forms the foundation of the drug's physiological effect by modulating blood vessel tone.


Modification of Cardiac Workload via Preload Adjustment

The widespread relaxation of blood vessels, predominantly in the extbfvenous system, modifies the body’s hemodynamic profile. By widening the veins, the mechanism increases their capacity to pool blood, consequently reducing the volume of blood returning to the heart ( extbfPreload). This systemic adjustment lowers the pressure and volume within the heart chambers, which produces a resultant reduction in myocardial oxygen demand—an expected physiological outcome of this pathway.


Mechanistic Limitations and Onset Kinetics

The pharmacological effect is subject to functional constraints inherent to the pathway itself, such as Nitrate Tolerance, where continuous signaling causes the mechanism to become less responsive over time. Furthermore, the necessity for the drug to undergo metabolic extbfbiotransformation to release NO means the effect has a relatively slow onset, reflecting that the mechanism operates through prolonged pathway modulation.

Dosage and Administration Information

How to Use Ismo-20: Official Administration Guidelines

Ismo-20 is an immediate-release oral tablet prescribed for long-term use, and its administration must strictly follow the defined protocols to ensure consistent efficacy. The fundamental principle governing its use is the adherence to a specific dosing schedule designed to prevent pharmacological tolerance.


Administration and Dosing Schedule

Category Official Administration Guideline
Route & Preparation The oral tablet must be swallowed whole with fluid; it is not to be crushed, chewed, or split.
Standard Dosing The recommended regimen is 20 mg administered twice daily. Initial dosing may start as low as 5 mg twice daily, increasing to maintenance over the first few days. Official guidelines allow for maintenance doses up to 120 mg daily.
Dosing Schedule The two daily doses must be taken in an asymmetric pattern, specifically seven hours apart (e.g., upon awakening and seven hours later). This schedule is mandatory to provide a daily nitrate-free interval.

Procedural and Cessation Rules

This medication is not intended for use in addressing an acute episode, as its onset of action is not rapid enough for emergency relief. Dosage adjustments are not generally required for older adult patients or those with hepatic or renal impairment, although caution is advised. Safety and efficacy have not been established for pediatric use.

Treatment is intended for long-term administration and must not be discontinued suddenly. When ceasing long-term therapy, the dosage and frequency must be tapered gradually. If a dose is missed and the next scheduled dose is nearly due, the procedural rule is to skip the missed dose and resume the regular schedule, avoiding a double dose.

Recent Clinical Evidence

Research Evidence: Overview of Studies for Ismo-20

This summary describes the clinical research conducted on Isosorbide Mononitrate (Ismo-20), focusing on the types of studies performed, the outcomes measured, and what remains unclear in the evidence, according to authoritative sources. This information is for context only and is not medical advice.


The Research Landscape for Ismo-20

Research used to support the approved indication comes primarily from Randomized Controlled Trials (RCTs). These studies involve randomly assigning patients to receive either the medicine or a placebo to observe differences in measured outcomes. This design is often supplemented by systematic reviews and meta-analyses. The focus of this research is on understanding patterns related to outcomes related to physical discomfort and outcomes reflecting daily functioning.


Evidence for Use in Preventing Angina Pectoris

The main body of research centers on its primary study indication: the prophylaxis (prevention) of chronic stable angina, which are conditions characterized by fluctuating or episodic manifestations of chest pain. Studies explored adult patients and monitored key patient-reported outcomes describing perceived discomfort.

Research Focus: Functional Capacity and Symptom Control

Studies monitored changes in exercise tolerance, reporting patterns where outcomes reflecting daily functioning or activity level were measured. Research observed that specific medicine-free intervals were present in study designs used to assess functional outcomes, due to the documented loss of action (tolerance).


Evidence for Use as Adjunctive Therapy in Congestive Heart Failure

Research has explored the use of Ismo-20 as a co-therapy in conditions associated with acute or disruptive episodes, such as congestive heart failure (CHF). The findings were mixed depending on the specific type of heart failure studied. This inconsistency means that evidence contributes to the broader evidence landscape but provides limited or uncertain insight into the potential role for all heart failure patients.


Key Uncertainties and Research Gaps

Long-term effects are not fully established. The typical duration of the key functional outcome studies is often short-term (e.g., 4 to 12 weeks). There is limited information available from RCTs specifically dedicated to assessing whether taking Ismo-20 was associated with changes in major, long-term cardiac outcomes. Additionally, data for certain groups remain insufficient, including for children and pregnant women. Overall, while research describes patterns related to patient discomfort and functional capacity, certainty remains low regarding long-term impact.

Frequently Asked Questions (FAQ)

Common questions about Ismo-20 (FAQ)

Q: Is Ismo-20 the same as other heart medicines like Imdur or mononitrate?

Ismo-20 contains the active ingredient Isosorbide Mononitrate. Official documents clarify that this is the same active chemical compound found in other brand names of the drug. The active ingredient itself is known as isosorbide mononitrate, which belongs to a class of medicines called organic nitrates.


Q: Does Ismo-20 have a generic version available?

The active ingredient, Isosorbide Mononitrate, is available as a generic medicine, in addition to various brand-name products. Generic medications contain the exact same active ingredient and meet the same regulatory standards for quality and effectiveness as the brand-name versions.


Q: How does Ismo-20 affect blood pressure?

Ismo-20 works as a vasodilator, meaning it widens blood vessels. According to official product information, a common effect is hypotension (low blood pressure). This can sometimes lead to side effects such as dizziness or lightheadedness.


Q: Why do people sometimes say they feel a throbbing sensation after taking Ismo-20?

The throbbing sensation that users describe is commonly linked to the drug's vasodilating effect, which causes the blood vessels to widen. This effect frequently manifests as a headache when first starting the treatment. Regulatory documents note that the occurrence of a headache can be a sign that the medication is actively working.


Q: Can Ismo-20 affect my ability to drive or operate machinery?

Official warnings state that side effects like dizziness, tiredness, or blurred vision may occur, particularly at the beginning of treatment. Regulatory documents indicate that patients who experience these symptoms should refrain from driving or operating machinery. The effects may be intensified by alcohol consumption.


Q: Is there a risk of becoming dependent on Ismo-20?

Regulatory documents indicate that abrupt cessation of the medication should be avoided, and the dosage is typically tapered off under medical supervision. While the clinical significance for routine use is not fully established, true physical dependence has been documented in high-exposure industrial settings involving nitrates.


Q: What should be done if an interaction with another drug is suspected?

Regulatory documents strictly prohibit co-administration with certain drug classes due to the risk of severe, life-threatening hypotension or circulatory collapse. Official labels identify severe, life-threatening hypotension as a risk. If symptoms of this reaction occur, regulatory guidance directs seeking immediate emergency medical attention.


Q: Is it important to take Ismo-20 at the exact same time every day?

Official administration guidelines focus on adhering to an asymmetric dosing schedule, such as taking the two daily doses seven hours apart. This specific time separation is mandatory to ensure a daily nitrate-free interval, which helps prevent the body from developing tolerance to the drug's effects.


Q: What is the difference between Ismo-20 and sublingual nitroglycerin?

Ismo-20 contains Isosorbide Mononitrate, which is classified as having a relatively slow onset of action and a prolonged effect, making it suitable for long-term prevention. In contrast, sublingual (under-the-tongue) nitroglycerin is a short-acting nitrate used specifically for the immediate relief of an acute episode of chest pain.


Q: Can Ismo-20 be taken with common pain relievers like Tylenol or ibuprofen?

Official patient information indicates that aspirin and/or acetaminophen (Tylenol) are often used to relieve headaches caused by the medication without reducing its effectiveness. Regulatory documents typically focus on aspirin and acetaminophen; they do not specifically address the concomitant use of non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen.


Q: What does the '20' in Ismo-20 refer to?

In pharmaceutical naming conventions, the number often refers to the strength of the tablet. The '20' in Ismo-20 likely corresponds to the standard strength of the immediate-release tablet, which is frequently labeled as 20 mg.


Q: Are there any specific lifestyle changes recommended while taking Ismo-20?

Because the medicine can cause dizziness due to low blood pressure, official patient information notes that avoiding standing up too quickly from a sitting or lying position may help to minimize the risk of lightheadedness and dizziness caused by the medication.


Q: How does Ismo-20 compare to isosorbide dinitrate?

Regulatory documents describe Isosorbide Mononitrate (the active ingredient in Ismo-20) as the major biologically active metabolite of isosorbide dinitrate. This characteristic contributes to its high bioavailability and consistent blood concentration, factors noted to support its use for consistent long-term treatment.


Q: Is Ismo-20 a type of blood thinner?

No. Official documents classify Ismo-20 as a Vasodilator and an Organic Nitrate. It acts by widening blood vessels, reducing the heart's workload. It is not classified as an anticoagulant or antiplatelet agent, which are commonly known as blood thinners.


Q: Does Ismo-20 affect cholesterol levels?

Official product information notes that Ismo-20 may interfere with certain laboratory tests. This includes tests used to measure cholesterol levels, which could potentially result in false test results.


Q: Are special blood tests required before prescribing Ismo-20?

According to clinical monitoring guidelines, routine laboratory monitoring is not typically required solely for the safe dose adjustment of this medication. Monitoring is typically based on clinical observations, which include blood pressure, heart rate, and symptom evaluation.


Q: What is the difference between immediate-release and extended-release forms of nitrates?

Ismo-20 is an immediate-release form, meaning the active ingredient is released into the body relatively quickly, necessitating an asymmetric twice-daily dosing schedule. In contrast, extended-release forms of the same drug are designed for once-daily administration to sustain therapeutic levels over a longer period and simplify the routine.

How should Ismo-20 be stored and disposed of?

How to Store and Dispose of ISMO-20 (Isosorbide Mononitrate)

ISMO-20 must be stored under specific environmental and safety conditions as mandated by regulatory authorities to maintain product integrity.


Storage Requirements

Condition Requirement
Temperature Store at room temperature, away from excess heat.
Protection Protect from direct sunlight and excess moisture; do not store in the bathroom or freeze.
Container Keep the medicine in its original container, tightly closed.
Shelf-Life Do not use the medicine after the expiry date shown on the carton.

Disposal and Safety

ISMO-20 must be stored out of the reach and sight of children, utilizing locked safety caps when present.

For disposal, do not throw away unused or expired medicine in household trash or wastewater. Patients must ask a pharmacist for the proper method to discard the medicine, as these measures protect the environment.

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

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