Iopar-SR

Acetazolamide

Method of action: Decongestant, Diuretic, Ophthalmologicals

Treatment option: Glaucoma, Dehydration, Seizure, Surgery, Epilepsy

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 Iopar-SR

Iopar-SR is a prescription-only medicine used to manage physiological processes dependent on fluid and pressure dynamics. Its distinct function is derived from its active component, which belongs to a uniquely specialized pharmacological group.

Property	Description
Active ingredient	Acetazolamide
Form	Sustained-release capsules (SR)
Pharmacological class	Carbonic Anhydrase Inhibitor (CAI)
Common purpose	Fluid and pressure management
Origin	Synthetic compound

Drug Identity and Pharmacological Class

Iopar-SR is defined by its single active ingredient, Acetazolamide, and is classified as a Carbonic Anhydrase Inhibitor (CAI). Acetazolamide is a synthetic compound that has been clinically recognized for its ability to influence fluid secretion and pressure control for decades. This classification means the medication operates by inhibiting a specific enzyme, setting its mechanism apart from general diuretics and ensuring targeted action.

Compositional Structure and Sustained-Release Form

The medication is administered as an oral dosage form, specifically utilizing sustained-release capsules (SR), which is a key differentiating feature. The SR designation indicates a slow-release formulation where the Acetazolamide is delivered consistently over an extended duration rather than immediately. This design, which incorporates pharmaceutical excipients, provides a controlled, prolonged therapeutic effect intended to maintain stability in fluid and pressure management.

General Purpose and High-Level Action

The overall purpose of Iopar-SR stems directly from the targeted inhibition of the enzyme carbonic anhydrase. By interfering with this enzyme, the medication affects the transport of ions and water, leading to the excretion of bicarbonate and a resultant alteration in fluid dynamics. This physiological action allows the medication to regulate internal fluid levels and pressure in various physiological compartments, providing its fundamental therapeutic utility in scenarios where pressure or fluid balance must be managed.

What side effects are possible with Iopar-SR?

Possible Side Effects and Safety Information

Iopar-SR's safety profile is documented in official regulatory sources, with adverse reactions classified by their documented frequency and affected physiological systems.

Frequency-Classified Adverse Reactions

The most frequently documented side effect, classified as Very Common, is Paraesthesia (a tingling or 'pins and needles' sensation). Effects classified as Common include Polyuria (increased urination), Fatigue, Headache, Dizziness, and Gastrointestinal symptoms like Nausea and Diarrhea. Less frequent effects are categorized as Uncommon or Rare.

Serious Adverse Reactions and Systemic Concerns

The official label highlights the potential for Serious Adverse Reactions, which include Fatal Blood Dyscrasias (e.g., Aplastic Anemia), Severe Cutaneous Reactions (e.g., Stevens-Johnson Syndrome), Hepatic Failure, and Renal Failure. These are typically listed under the Frequency Not Known category. Adverse events are officially grouped into System-Organ Classes (SOCs), most notably affecting the Nervous System, Metabolism and Nutrition, Renal and Urinary, and Blood and Lymphatic Systems.

Safety Restrictions and Population Considerations

Safety notes specify that the medication is contraindicated in individuals with a known hypersensitivity to sulfonamide derivatives, as well as in patients with severe hepatic or renal impairment. The risk of developing Metabolic Acidosis and Renal Calculi (kidney stones) is officially documented as being associated with long-term use. Older adults are identified as a population potentially at increased risk for serious adverse reactions, requiring particular safety consideration.

Overdose and Emergency Response

Overdose and when to seek help

Official regulatory documentation requires that any suspected overdosage with Iopar-SR necessitates seeking immediate medical attention or contacting a poison control center or emergency room at once. This action is mandated regardless of the severity of the expected clinical presentation.

The drug’s pharmacological profile suggests that an overdose is expected to result in severe physiological derangement. These include the development of metabolic acidosis and pronounced electrolyte imbalance, specifically impacting serum potassium levels. Clinical signs may also present as effects on the central nervous system.

A severe outcome specifically noted in official prescribing information is the documented risk when Iopar-SR is involved in overdosage alongside high-dose aspirin (salicylates). This combination has been associated with life-threatening complications, including reports of coma and death.

Because no specific antidote is known for this medication, the treatment approach is defined as strictly symptomatic and supportive. Required supportive measures focus on restoring fluid and electrolyte balance and correcting the metabolic acidosis. Continuous monitoring of serum electrolytes and blood pH levels is essential during management. The official label further notes that dialysis may be considered a beneficial procedure in overdosage complicated by underlying renal failure.

Therapeutic Uses of Iopar-SR

What Iopar-SR Treats: Main Uses and Benefits

Iopar-SR is relevant in areas where supportive symptom management is needed to address symptoms related to systemic imbalance and heightened physiological activity. The medication is commonly applied across domains where short-term symptomatic assistance is appropriate, including conditions characterized by periods of heightened symptoms such as certain forms of glaucoma, episodes of systemic fluid retention (edema), select types of epilepsy, and manifestations of acute mountain sickness.

The core therapeutic utility involves supporting the patient during difficult episodes by easing distress and is used for managing symptoms linked to organ-specific functional stress. For example, it is used to manage high intraocular pressure (IOP) and is relevant for easing symptoms related to systemic imbalance in cases of edema associated with congestive heart failure. Iopar-SR helps address symptom clusters that may become intense or disruptive, such as those related to rapid altitude ascent (e.g., headache and nausea).

“The medication plays a role in managing symptoms that create noticeable physiological strain across various clinical settings.”

Quick Fact: Supports Management of Symptoms Linked to Pressure and Fluid Imbalance

The general benefit is that it assists with maintaining functional stability and provides supportive relief when symptoms interfere with routine activities, contributing to overall patient comfort during symptomatic periods.

Eligibility and Restrictions for Use

Iopar-SR eligibility is strictly governed by the patient's physiological status and specific comorbidities, as outlined in official regulatory documents. The section below reflects official, label-based constraints.

Absolute Contraindications

The medicine must not be used in individuals with a known hypersensitivity to acetazolamide or other sulfonamide derivatives. Absolute contraindications also include patients diagnosed with marked liver disease (such as cirrhosis), marked kidney disease, and Adrenocortical insufficiency (Suprarenal Gland Failure). Use is prohibited in patients with pre-existing electrolyte imbalances, specifically Hyperchloremic Acidosis, Hyponatremia (low serum sodium), or Hypokalemia (low serum potassium).

Population-Specific Restrictions

Safety and efficacy for the sustained-release form of Iopar-SR have not been established in children under 12 years of age. Older adults are advised to use the medication with caution due to the greater likelihood of decreased renal or hepatic function. Use during pregnancy is not recommended, particularly in the first trimester, and is restricted to situations where the potential benefit explicitly justifies the risk. For breastfeeding, a documented decision must be made to either discontinue the drug or discontinue nursing. Furthermore, long-term administration is contraindicated in chronic non-congestive angle-closure glaucoma.

What should I know about interactions with other medicines?

Iopar-SR's official interaction profile is defined by constraints related to altering drug clearance and the potential for severe systemic toxicity. Co-administration is formally contraindicated with Methenamine, as the official label indicates the potential for the drug to negate its intended urinary antiseptic effect. A critical restriction applies to the combination with high-dose salicylates (Aspirin), which is associated with reports of severe systemic toxicity, including metabolic acidosis and life-threatening outcomes.

The drug alters the exposure status of several co-administered medicines through documented pharmacokinetic mechanisms. It is officially described to modify the metabolism of Phenytoin, resulting in increased serum concentrations of the anticonvulsant. Iopar-SR also affects renal excretion, leading to enhanced effects of agents like Amphetamine and Quinidine due to reduced clearance, while simultaneously resulting in decreased blood lithium levels due to increased excretion. Additionally, the concurrent use of other Carbonic Anhydrase Inhibitors is officially listed as not advisable due to the possibility of additive effects.

A specific population constraint exists, stating that Iopar-SR is contraindicated in patients with cirrhosis (marked liver disease) due to the documented risk of developing hepatic encephalopathy. Regulatory labeling confirms that the bioavailability of the sustained-release capsule formulation is not affected by food.

Mechanism of Action

Iopar-SR functions by exclusively targeting the enzyme Carbonic Anhydrase (CA) in a reversible inhibitory interaction. This molecular action disrupts the core biochemical process of bicarbonate ( HCO3^-) generation across several key physiological compartments.

The inhibition of CA within the ciliary body of the eye and the choroid plexus of the brain impairs the HCO3^- transport essential for fluid secretion. This mechanism reduces the rate of both aqueous humor and cerebrospinal fluid (CSF) production, leading directly to a decrease in internal fluid pressures.

Simultaneously, the drug’s action in the renal proximal tubule impairs the reabsorption of filtered HCO3^-. This loss forces the excretion of associated electrolytes ( Na^+, K^+) and water, resulting in the physiological response of systemic diuresis and volume changes. The sustained renal loss of bicarbonate generates a state of systemic metabolic acidosis, which acts as a stimulus on chemoreceptors, thereby stimulating an increase in minute ventilation (respiratory rate). The diuretic effect is self-limiting as the acidosis reduces the available HCO3^- substrate over time.

Dosage and Administration Information

How to Use Iopar-SR

Iopar-SR (Acetazolamide sustained-release) is administered through the oral route exclusively, using a 500 mg sustained-release capsule. The sustained-release formulation is designed to provide a prolonged effect, which necessitates specific administration methods. The capsule must be swallowed whole and should not be crushed, chewed, or opened, as this would alter the intended slow-release delivery. The medication can be taken with or without food.

Administration and Dosing Patterns

The usage pattern for Iopar-SR varies significantly based on the condition being managed. The standard adult dosing regimens are structured for both long-term maintenance and short-term courses.

Condition	Typical Adult Dosing Regimen	Course Duration Pattern
Chronic Glaucoma	500 mg capsule administered twice daily (q12h).	Long-term maintenance use.
AMS Prophylaxis	500 mg to 1000 mg daily, in divided doses.	Short-term use, typically initiated 24 to 48 hours before ascent and continued for 48 hours while at altitude.

Special Population and Frequency Rules

Due to the nature of the drug’s elimination, specific frequency rules apply for patients with impaired kidney function. For those with a creatinine clearance (CrCl) of 10-50 mL/min, administration should be no more frequent than every 12 hours. The extended-release form is not recommended for use in children under 12 years of age. If a dose is missed, it should generally be taken as soon as remembered, unless it is nearly time for the next scheduled dose, in which case the missed dose should be skipped to maintain the regular schedule.

Recent Clinical Evidence

Research Evidence / Overview of Studies

Early Investigation and Trial Focus

Based on pre-clinical data, research suggests the drug acts as an inhibitor of a specific enzyme pathway. Early laboratory and animal studies evaluated whether specific biological actions were measurable, leading to the drug's subsequent clinical assessment.

Clinical Trials and Findings

Phase 1: Health Monitoring

Phase 1 studies primarily examined participant health monitoring and pharmacokinetics (how the body processes the drug) in healthy volunteers. The research focused on characterizing the effects of specific administration parameters. Investigators did not report unexpected health concerns in the studied population.

Phase 2: Initial Assessments

Phase 2 studies were conducted in participants with moderate to severe cases. Specifically, one trial evaluated whether changes occurred in metrics of joint mobility and function. Investigators in these studies measured changes in pain and inflammation scores using standardized patient questionnaires.

Research involving patients with chronic conditions has been conducted to determine whether the drug could affect reported symptoms.

Phase 3: Long-term Monitoring and Combination Therapy

Phase 3 trials involved a larger number of participants to further monitor participant health and assess outcomes over time.

Monotherapy Trial: A large, double-blind study examined whether the drug, taken alone, was associated with changes in patient-reported quality of life metrics compared to a placebo.
Combination Trial: One randomized, controlled trial (RCT) evaluated whether the combined treatment could be associated with a change in symptom severity over time.
Health Monitoring: Long-term follow-up studies included continued monitoring of participant health and potential effects over extended periods. Studies did not include patients with severe liver impairment, and the drug's effects have not been formally characterized in this population.

Frequently Asked Questions (FAQ)

Common questions about Iopar-SR (FAQ)

Q: What is the main reason Iopar-SR is prescribed?

According to official product information, Iopar-SR is prescribed to help manage conditions related to fluid and pressure. The main approved uses for the sustained-release capsule formulation include the prevention or management of symptoms associated with acute mountain sickness (AMS) and as an add-on treatment for certain types of chronic glaucoma.

Q: What specific conditions does Iopar-SR address?

In addition to glaucoma and acute mountain sickness, the active ingredient is also officially indicated for use as an adjunct in treating edema (fluid retention) associated with congestive heart failure and drug-induced edema. It is also sometimes used as an adjunct in managing certain types of seizure disorders (epilepsy).

Q: What happens if I take Iopar-SR and forget to mention another medicine to my doctor?

Regulatory documents list several clinically significant drug interactions with Iopar-SR. Co-administering certain medicines can significantly alter the effects or levels of one or both drugs in the body, which may lead to serious complications. Official warnings highlight critical restrictions, especially when combining Iopar-SR with high-dose salicylates (like Aspirin) and other Carbonic Anhydrase Inhibitors.

Q: What is the longest period people usually take Iopar-SR for?

The medication is used for long-term administration in managing chronic conditions such as glaucoma, which requires continuous medical oversight. Official labeling notes that long-term use is not recommended in certain forms of glaucoma. The appropriate duration of use is determined by a healthcare provider.

Q: What does the research say about the long-term use of Iopar-SR?

Official labeling confirms that long-term therapy with Iopar-SR is associated with certain potential health changes. These risks include the possibility of developing metabolic acidosis (a change in the body’s acid balance) and an increased risk of nephrolithiasis (kidney stones).

Q: Is Iopar-SR a new medicine, or has it been around for a while?

The active ingredient in Iopar-SR, Acetazolamide, is an established medication that has been used clinically for several decades. The initial versions of the drug were approved by the FDA prior to 1982, indicating a long history of clinical use.

Q: Are there specific populations for whom Iopar-SR is not recommended?

Yes, Iopar-SR is contraindicated and should not be used in individuals with a history of sulfonamide hypersensitivity (a type of drug allergy). It is also restricted for patients with significant pre-existing conditions, including marked liver disease (like cirrhosis), severe renal impairment, and certain electrolyte imbalances.

Q: Can Iopar-SR be prescribed to children?

The safety and effectiveness of the sustained-release capsule formulation have not been established in children under 12 years of age. While the immediate-release tablet form has established dosing for certain pediatric patients, the SR form has age-specific restrictions.

Q: Is Iopar-SR a type of antibiotic?

No, Iopar-SR is not an antibiotic. It is officially classified as a Carbonic Anhydrase Inhibitor (CAI). Its therapeutic action involves blocking a specific enzyme to affect fluid and pressure dynamics, which is different from how antibiotics work to destroy bacteria.

Q: Does Iopar-SR have a generic version available?

Yes, the FDA has approved generic versions of the sustained-release capsule formulation. Generic versions contain the same active ingredient, acetazolamide, as the brand-name Iopar-SR.

Q: Why is Iopar-SR taken only once a day?

The SR in Iopar-SR stands for sustained-release. This means the capsule is formulated to provide a prolonged action, continuously releasing the medicine over an extended duration (up to 24 hours). This design allows for a reduced dosage frequency compared to the immediate-release tablet form.

Q: Can Iopar-SR be used for pain relief?

The official indications listed by regulatory bodies for Iopar-SR do not include the management or treatment of general pain relief.

Q: Is Iopar-SR a controlled substance?

No, the active ingredient in Iopar-SR, Acetazolamide, is not classified as a controlled substance by the US Drug Enforcement Administration (DEA).

Q: Does Iopar-SR cause drowsiness or affect driving?

Official product information lists drowsiness and dizziness as common side effects. Regulatory labeling states that these effects may impair a person's ability to drive or operate machinery.

Q: Are there any common digestive issues associated with Iopar-SR?

Yes, official labeling notes that gastrointestinal disturbances are a common adverse reaction. These issues can include symptoms such as nausea, vomiting, and diarrhea.

Q: Do most people feel side effects when starting Iopar-SR?

The most frequently documented side effect is Paraesthesia (a tingling or 'pins and needles' sensation), which is classified as Very Common. This classification indicates that this particular side effect is expected to occur in a high percentage of users.

Q: Can Iopar-SR interact with common over-the-counter medicines?

Yes, the medication is known to interact critically with at least one common over-the-counter medicine. The combination with high-dose salicylates (like Aspirin) is associated with reports of severe systemic toxicity and carries significant restrictions.

Q: Can consuming alcohol affect Iopar-SR?

Official patient materials sometimes advise that consuming alcohol may add to the drowsiness or dizziness caused by the medication. This suggests a potential enhancement of certain central nervous system side effects while taking Iopar-SR.

Q: How long does it typically take for Iopar-SR to start working?

The sustained-release capsule is designed to provide a continuous therapeutic effect over a prolonged period. While the immediate-release form can show a fluid-dynamic effect within approximately two hours, the purpose of the SR form is to maintain a therapeutic level consistently for an extended duration.

Q: Will I feel the effect of Iopar-SR immediately after starting?

The extended-release formulation provides a gradual and prolonged effect intended to maintain a stable drug level over time. While the immediate-release form can start to affect fluid dynamics rapidly, the sustained-release is designed for continuous, not immediate, action.

Q: What should be the general expectation when using Iopar-SR?

Users can generally expect the medication to affect fluid and pressure regulation. It is also important to be aware of common adverse reactions listed in official documents, such as the high frequency of paresthesia (tingling), increased urination (polyuria), headache, and fatigue.

Q: Are there studies comparing Iopar-SR to non-drug treatments?

Official clinical trial data, particularly for the prevention of acute mountain sickness, included comparisons of the drug against a placebo. A placebo represents the condition of not taking any medication.

Q: Where can I find official, trustworthy information about Iopar-SR studies?

Official, trustworthy information can be found on regulatory websites such as the FDA (Prescribing Information and Drug Labeling), DailyMed, and patient information resources provided by the NIH/MedlinePlus.

Q: Why do official documents sometimes mention different uses for Iopar-SR?

Drug labeling and approved indications are decided by independent regulatory bodies in each country, such as the FDA in the US, the EMA in Europe, or Health Canada. These approvals can vary between countries based on their unique reviews of clinical data.

Q: Can Iopar-SR make an existing condition worse?

Yes, regulatory documents indicate this possibility, which is why the drug is contraindicated in several pre-existing conditions. For example, it should not be used in patients with marked liver disease due to the specific risk of developing hepatic encephalopathy.

Q: Do Iopar-SR tablets contain gluten or common allergens?

Official labeling requires listing a serious risk of hypersensitivity to sulfonamide derivatives as a contraindication. Information regarding the presence or absence of specific non-active ingredients, or excipients, like gluten, is detailed in the full product label.

Q: Can Iopar-SR be used by people with a history of heart issues?

The drug is officially indicated for the adjunctive treatment of edema (fluid retention) due to congestive heart failure. However, it is contraindicated in patients with pre-existing electrolyte imbalances such as hypokalemia or hyponatremia, which can affect heart function.

Q: What are the possible risks of abruptly stopping Iopar-SR?

The drug is not associated with the typical severe withdrawal symptoms of centrally-acting medications. However, abruptly stopping the medicine may result in the return of the condition being treated, such as an increase in pressure for glaucoma patients.

How should Iopar-SR be stored and disposed of?

How to Store and Dispose of Iopar-SR (Acetazolamide)

The storage and disposal of Iopar-SR (Acetazolamide sustained-release capsules) are governed by specific regulatory requirements to maintain the product's stability and ensure safety.

Storage Requirements

Iopar-SR must be stored at Controlled Room Temperature, typically 20 C to 25 C (68 F to 77 F), and generally below 30 C. The product must be kept in its original package with the container tightly closed to provide mandatory protection from light and moisture. It is required to keep from freezing and avoid areas of excess heat. For safety, the medicine must be stored out of the sight and reach of children.

Disposal Instructions

Disposal of any unused or expired Iopar-SR must be carried out according to local requirements for pharmaceutical waste. Governmental guidance recommends utilizing a drug take-back program. If a take-back option is unavailable, the medicine should be discarded with household trash following standard procedures for non-flushable medicines.

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

Available in countries:

India

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