Gliclazide

Quick links to important sections

Gliclazide

Selected form

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 Gliclazide

Quick Facts: Gliclazide

Property Description
Active Ingredient Gliclazide (Glyclazide)
Form Oral Solid Formulation (Tablets)
Pharmacological Class Sulfonylurea (SU) Class, Insulin Secretagogue
Common Use Management of high blood sugar in Type 2 Diabetes
Origin Synthetic Compound (Second-Generation)

Gliclazide: Defining the Drug Entity and Its Class

Gliclazide is a synthetic chemical compound and the active ingredient in a prescription-only oral antidiabetic drug (OAD) used to manage high blood sugar. This compound belongs to the sulfonylurea (SU) class, specifically categorized as a second-generation compound. Its chemical structure, defined by the formula C15H21N3O3S, positions it as an insulin secretagogue. This means Gliclazide's action is to directly encourage insulin release, differentiating it from agents like biguanides which primarily reduce the body's glucose production. The drug is globally recognized for its established role in diabetes care, supported by numerous pharmacological studies and its inclusion on the World Health Organization's (WHO) Model List of Essential Medicines.


General Purpose and Forms

The general purpose of Gliclazide is to help patients achieve and maintain better glycemic control by lowering the high blood glucose (hyperglycemia) characteristic of Type 2 Diabetes Mellitus. Gliclazide is clinically recognized for stimulating the beta-cells of the pancreas to release stored insulin. A typical use scenario for Gliclazide is in the long-term management of adults diagnosed with Type 2 Diabetes, where diet and exercise alone have proven insufficient. The drug is administered via the oral route as an oral solid formulation (tablets), including the distinct modified-release (MR) form. The MR tablets are designed for slow, consistent delivery of the active ingredient over many hours, which provides the patient benefit of a more stable drug concentration throughout the day, often permitting convenient once-daily administration.

What side effects are possible with Gliclazide?

Possible Side Effects and Safety Information

This section outlines the officially documented adverse effects and safety constraints of Gliclazide, based strictly on government regulatory documents such as the Summary of Product Characteristics (SmPC) and equivalent prescribing information.

Documented Adverse Reactions and Frequency

The most frequent adverse reaction documented in regulatory materials is Hypoglycaemia (low blood sugar), which is classified as Common (occurring in 1/100 to <1/10 patients). Other effects classified as Common include a cluster of Gastrointestinal disorders such as nausea, vomiting, abdominal pain, diarrhoea, and dyspepsia.

Adverse effects have been grouped by the body systems affected, encompassing Metabolism and nutrition disorders, Gastrointestinal disorders, Skin and subcutaneous tissue disorders (e.g., rash, pruritus), and Blood and lymphatic system disorders (e.g., changes in blood cell counts).

Serious Adverse Reactions and Safety Constraints

Regulatory documents highlight several serious adverse reactions, including: Severe prolonged hypoglycaemia (which carries a risk of neurological damage or coma), severe Blood disorders (such as agranulocytosis and aplastic anaemia), and life-threatening Liver disorders (e.g., hepatitis, cholestatic jaundice).

Specific Safety Constraints:

Constraint Area Regulatory Requirement
Population Contraindicated in individuals with severe renal or hepatic insufficiency, as this significantly increases the risk of severe, prolonged hypoglycaemia.
Conditions Contraindicated in Type 1 Diabetes Mellitus, diabetic keto-acidosis, and diabetic pre-coma.
Drug-Specific Contraindicated for use with systemic or oromucosal Miconazole.

Hypoglycaemia is noted to be more likely to occur under specific patient conditions, such as after a low-calorie diet, strenuous exercise, or alcohol intake, as documented in the medicine’s official safety information.

Overdose and Emergency Response

Overdose and When to Seek Help

Official regulatory documentation states that an overdose of Gliclazide primarily results in hypoglycemia (low blood sugar), which is an exaggerated effect of the medication. The initial clinical signs of this manifestation may include sweating, palpitations, intense hunger, tremor, and anxiety.

Severe Manifestations and Required Action

Classification Official Regulatory Statement
Severe Outcomes The condition may progress to severe and prolonged hypoglycemia, potentially leading to seizures, neurological impairment, and coma (loss of consciousness).
Emergency Action Seek immediate medical attention for any sign of severe low blood sugar or if an excessive dose is taken. If a patient is unconscious, emergency medical services must be contacted immediately, as urgent intravenous glucose administration and hospitalization are required.
Management Note No specific pharmacological antidote is known; supportive treatment includes giving sugar or glucose. Hospital observation is mandated due to the risk of recurring hypoglycemia.

Population Considerations

Regulatory documents note that the risk of severe and prolonged hypoglycemia following overdose is increased in elderly subjects and patients with impaired hepatic or renal function.

Therapeutic Uses of Gliclazide

Primary Use: Managing Chronic High Blood Sugar in Adults

Gliclazide is commonly used for managing Type 2 Diabetes in adults when blood glucose levels are insufficiently controlled by diet, physical exercise, and weight loss alone. It is applied in clinical settings when symptoms related to systemic imbalance and increased physiological stress persist, and is applied across domains where additional symptomatic support is needed. The drug is considered relevant when symptoms that interfere with daily functioning may be present due to the chronic inability to self-regulate blood glucose. The core indications Gliclazide is relevant for include long-term management of Type 2 Diabetes, may be part of symptomatic management by supporting blood sugar, and addressing persistent hyperglycemia.


Therapeutic Benefit: Supporting Glycemic Control

The primary therapeutic benefit may be part of symptomatic management by supporting glucose management in the relevant therapeutic domains. It is used for managing the symptom cluster of chronically elevated blood glucose levels and supports the patient during phases when symptoms become more noticeable. By being applied in addressing persistent hyperglycemia, the medication provides supportive relief when symptoms interfere with routine activities and contributes to easing the overall symptom load during symptomatic periods.


Quick Fact: Support for Blood Glucose Management

Feature Description
Primary Condition Type 2 Diabetes Mellitus (Adults)
Symptom Domain Chronically Elevated Blood Glucose Levels
Clinical Context Insufficient control from diet and exercise alone
Patient Benefit Plays a role in managing glucose levels

Eligibility and Restrictions for Use

Eligibility Map: Who Can and Cannot Use Gliclazide

Official regulatory documents define Gliclazide's eligibility based on patient population, disease status, and organ function. The medicine is indicated for the treatment of Type 2 Diabetes Mellitus in adults when diet and exercise alone have proven insufficient.


Populations for Whom Use is Contraindicated

Use is absolutely prohibited for several groups, including patients with Type 1 Diabetes Mellitus or diabetic keto-acidosis. Gliclazide is also contraindicated in cases of severe renal failure or severe hepatic failure, as well as in patients with a known hypersensitivity to Gliclazide, other sulfonylureas, or sulfonamides.


Age and Physiological Restrictions

Population Regulatory Status
Pediatric (Under 18) Not recommended; safety and efficacy are not established.
Pregnancy Contraindicated; insulin is the preferred treatment.
Lactation (Breastfeeding) Contraindicated due to risk of neonatal hypoglycemia.

Conditional Use and Restrictions

Patients with mild to moderate renal or hepatic impairment may be prescribed Gliclazide, but use requires close patient monitoring. The medicine must be temporarily discontinued and replaced with insulin during periods of severe stress, trauma, acute infection, or major surgery.

What should I know about interactions with other medicines?

Interactions with other medicines and products

The official regulatory profile for Gliclazide focuses on interactions that significantly alter blood sugar levels, increasing the risk of either excessively low blood sugar (hypoglycemia) or poor blood sugar control.

Contraindicated and Not Recommended Combinations

Co-administration of Gliclazide with systemic Miconazole (oromucosal gel) is formally documented as contraindicated due to the high risk of severe potentiation of the hypoglycemic effect. The use of alcohol (ethanol) must be strictly avoided as it can severely potentiate the hypoglycemic reaction by inhibiting compensatory mechanisms. Similarly, the regulatory documents advise against combining Gliclazide with Phenylbutazone (systemic route), Danazol, and the herbal product St. John's Wort.

Pharmacodynamic and Pharmacokinetic Interactions

Pharmacodynamic interactions primarily involve other agents that lower blood glucose, such as insulin and metformin, leading to an additive effect and increased hypoglycemia risk. Other substances, including ACE Inhibitors, Fluconazole, and Beta-blockers, are also documented to potentiate the blood glucose lowering effect. The co-administration of Beta-blockers is further noted to potentially mask the common symptoms of hypoglycemia.

Pharmacokinetic interactions involve the metabolism of Gliclazide. Substances that inhibit the enzyme CYP2C9 (e.g., Fluconazole) may decrease Gliclazide clearance and increase plasma concentrations. Conversely, inducers like St. John's Wort can increase Gliclazide metabolism, potentially reducing its efficacy.

Mechanism of Action

Closing the Pancreatic KATP Channel

Gliclazide's action begins in the pancreatic β-cells by binding to the Sulfonylurea Receptor 1 (SUR1), a subunit of the ATP-Sensitive Potassium (KATP) channel complex. This interaction forces the channel to close, halting the efflux of potassium ions (K+) and initiating the depolarization of the cell membrane.

Triggering the Insulin Secretion Cascade

The membrane depolarization subsequently opens voltage-gated calcium channels, resulting in a rapid influx of calcium ions (Ca2+) into the β-cell. This calcium influx serves as the crucial biochemical signal that triggers the exocytosis of insulin granules, leading to a release of pre-synthesized insulin into the bloodstream.

⇣ Resulting Physiological Glucose Regulation

The resulting increase in secreted insulin facilitates the removal of glucose from the circulation by enhancing uptake in peripheral tissues and modulating hepatic glucose output. This mechanism, which depends entirely on the presence of functional β-cells, directly contributes to the regulation of systemic glucose concentration.

Dosage and Administration Information

Gliclazide is administered via the oral route as an oral solid formulation, available in both immediate-release (IR) and modified-release (MR) tablet forms. The proper use protocol is strictly defined by the specific formulation and its time-relationship to meals. MR tablets are generally taken once daily with the first main meal of the day (e.g., breakfast), while IR tablets may be taken once or twice daily with meals. Tablets must be swallowed whole with water and not crushed or chewed, a necessary constraint for the proper release of the active ingredient, particularly for the MR design.

The medicine is used as a long-term therapy, and the official labeled regimen establishes the dose ranges within which it is prescribed. Dosage adjustments, or titration, are performed based on the patient's metabolic response, typically requiring a minimum interval of at least one month between changes.

Formulation Initial Dose (Daily) Maximum Dose (Daily)
Modified-Release (MR) 30 mg 120 mg
Immediate-Release (IR) 40 mg to 80 mg 320 mg

For proper administration, if a dose is missed, the protocol is to skip the forgotten dose and take the next one at the usual time; a double dose must never be taken to compensate. For specific populations, the minimum starting dose is generally recommended for older adults with careful monitoring. Its use in children and adolescents under 18 years is not authorized, as efficacy and safety have not been established in the pediatric population.

Recent Clinical Evidence

Research evidence / Overview of studies for Gliclazide

This section outlines the types of research that have been conducted for Gliclazide, the main areas that studies have examined, and what remains uncertain in the evidence base, based on official regulatory and scientific literature.


Evidence for use in Glycemic Control (Short- and Medium-Term)

Research has utilized short-term to intermediate-term Randomized Controlled Trials (RCTs) and Systematic Reviews to investigate outcomes related to blood sugar control in studies involving Gliclazide. These studies focused on adult patients with Type 2 Diabetes whose blood sugar levels were not sufficiently managed by changes in diet and exercise alone. The core outcomes that studies monitored included measurements of the long-term glucose control biomarker, Glycated Hemoglobin ( HbA1c), and the shorter-term measure, Fasting Plasma Glucose (FPG). Studies also reported changes in outcomes like Body Weight as a secondary observation.

Findings describe patterns observed in the studies where HbA1c values shifted among populations receiving Gliclazide, compared to those receiving a control substance or other study agents. Real-World Observational Studies have also been applied in research contexts evaluating how Gliclazide is included in daily-life functional settings.


Evidence for use in Evaluating Long-Term Vascular Outcomes

Gliclazide was evaluated in a major, large-scale Randomized Controlled Trial (RCT) designed to assess long-term outcomes related to diabetes complications. This research focused on older adults with established T2DM and high cardiovascular risk factors. The study examined outcomes related to Major Vascular Events (such as heart attack and stroke) and Microvascular Events (related to kidney and eye disease). The research explored the use of an intensive glucose-lowering strategy, anchored by the Gliclazide Modified-Release ( MR) formulation, versus a standard control approach.

The large-scale trial reported measurements showing no difference in the primary composite macrovascular outcome (heart attack, stroke, and cardiovascular death) between the intensive control strategy and the standard control strategy during the intervention phase. The same trial described patterns in the composite microvascular outcome, which was primarily driven by observed measurements in new or worsening renal disease events.


Research Gaps and Areas of Uncertainty

The core research regarding long-term complication prevention was studied for using an intensive glucose-lowering strategy, meaning the findings are primarily about that strategy, and comparative evidence is lacking when trying to isolate Gliclazide's effects against certain newer classes of blood glucose-lowering drugs. Key limitations include that sample sizes were modest in some comparative analyses, and follow-up durations were limited to a few months in others. In some direct comparisons, certainty remains low, and research is ongoing to further characterize these effects.

Key Studies & References

  1. Gliclazide Oral Drug Information (MedlinePlus)

Frequently Asked Questions (FAQ)

Common questions about Gliclazide (FAQ)


Q: How quickly does Gliclazide generally start working to lower blood sugar?

Regulatory documents describe that Gliclazide plasma levels increase within the first six hours after administration. The presence of the drug in the bloodstream is documented to reach a plateau within several hours. Official guidance indicates that dose adjustments are typically evaluated after a minimum interval of two to four weeks to assess the full metabolic response.


Q: What is the difference between Gliclazide and Metformin?

Gliclazide is in the sulfonylurea class, which works by stimulating the pancreas to release more of the body’s own insulin. Metformin belongs to the biguanide class and acts through a different pathway, primarily by helping to reduce the amount of glucose produced by the liver. Official prescribing information indicates that Gliclazide may be used in combination with biguanides because of these distinct mechanisms.


Q: Is Gliclazide known to cause weight gain, according to research?

Research studies reviewed by regulatory bodies monitored changes in body weight as a secondary observation during clinical trials. Official patient-aligned information for Gliclazide's class, sulfonylureas, indicates that weight gain is a possible observation for some people using the medication.


Q: Is it common to feel a bit dizzy when first starting Gliclazide?

While dizziness itself is not listed as a separate adverse effect, it is a documented symptom of low blood sugar, or hypoglycemia. Hypoglycemia is listed in regulatory documents as a Common adverse reaction when using Gliclazide.


Q: Are there any long-term side effects associated with Gliclazide use?

Official regulatory documents highlight documented, serious adverse reactions that can occur, including severe prolonged low blood sugar, severe changes in blood cell counts (like agranulocytosis), and liver disorders (such as hepatitis). The medicine is intended for long-term therapy, and studies have focused on long-term outcomes related to glucose control, like HbA1c.


Q: Is Gliclazide part of combination therapy for diabetes?

Yes, regulatory documents confirm that Gliclazide can be prescribed as part of a combination therapy regimen. It is noted that it can be used alongside other antidiabetic agents, such as biguanides, alpha-glucosidase inhibitors, or insulin.


Q: Do studies suggest Gliclazide has cardiovascular benefits or risks?

A major controlled clinical trial was conducted to evaluate long-term outcomes, including Major Vascular Events such as heart attack and stroke. The research found no difference in the primary composite macrovascular outcome between the intensive glucose-lowering strategy using Gliclazide and the standard control strategy during the intervention phase.


Q: Are there certain foods or supplements that should not be taken with Gliclazide?

Official documents document a potential interaction and caution against the combination of Gliclazide with the herbal product St. John's Wort. Beyond this, certain dietary patterns, such as a low-calorie diet or irregular food intake, are described as conditions that increase the risk of low blood sugar.


Q: Does Gliclazide interact with common over-the-counter pain relievers?

Yes, official prescribing information indicates that certain common pain relievers, specifically those classified as non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, may interact. These medicines are documented to increase the blood glucose lowering effect of Gliclazide, raising the risk of low blood sugar.


Q: Is Gliclazide safe for older adults or elderly patients?

Regulatory guidance states that Gliclazide can be used for older adults, and the same dosing regimen as for younger patients is generally described in official information. No specific special instructions for the elderly are typically required, but monitoring of blood glucose is standard for all patients.


Q: Is Gliclazide known to interact with birth control pills?

Some regulatory-aligned patient information suggests that oral contraceptives may potentially increase blood sugar levels. When Gliclazide is used alongside these products, patients may require closer monitoring of their blood glucose levels.


Q: What is the connection between Gliclazide and sunlight sensitivity?

Official patient warnings advise that Gliclazide may be associated with increased sensitivity to sunlight, a reaction called photosensitivity. Official warnings describe that patients should report to a medical professional if their skin appears to be burning or reacts unusually to sun exposure, even when protective measures are used.


Q: Is there a generic version of Gliclazide available?

Yes, regulatory public assessment reports confirm that generic versions of Gliclazide are available. These generic products have been confirmed by regulatory bodies to be bioequivalent—meaning they contain the same active ingredient and work the same way—as the original brand-name product.


Q: Why are there different strengths of Gliclazide tablets?

The different strengths of Gliclazide tablets are available because the correct dose must be adjusted for each individual patient. Regulatory documents specify that the daily dose is determined and modified based on the patient's metabolic response, which includes their blood glucose and HbA1c levels.


Q: Can taking Gliclazide make you more tired than usual?

Unusual weakness and lassitude (lack of energy or tiredness) are documented as possible symptoms of low blood sugar, or hypoglycemia. Since hypoglycemia is a common adverse effect associated with Gliclazide, these symptoms may be experienced.


Q: Are there specific symptoms that indicate Gliclazide is working?

The main indication that Gliclazide is working is the measured improvement in blood sugar control, specifically the lowering of blood glucose and the long-term marker, Glycated Hemoglobin (HbA1c). These indicators of effectiveness are typically monitored objectively through regular laboratory tests.


Q: What is the risk of Gliclazide interacting with herbal supplements?

Official regulatory information documents an interaction and advises caution regarding the use of the herbal product St. John's Wort with Gliclazide. This combination is noted to potentially reduce the effectiveness of Gliclazide. For other herbal supplements, official safety information is often insufficient.


Q: Do official documents mention Gliclazide affecting mental clarity or mood?

Yes, official documents mention that hypoglycemia (low blood sugar), which is a common side effect, can affect mental state. Documented symptoms include poor concentration, confusion, reduced awareness and slowed reactions, and in some cases, depression.


Q: Is Gliclazide a blood thinner?

Gliclazide is not classified as a blood thinner, but it is documented in regulatory information as being capable of increasing the effects of certain medicines that reduce blood clotting, such as warfarin. This interaction is related to the blood coagulation system.


Q: Can Gliclazide be safely stored in warm climates?

Regulatory documents define strict storage requirements, including keeping Gliclazide at a temperature below 30°C (86°F) and protecting it from light and moisture. The storage requirements mean that in warm climates, care must be taken to ensure the medicine remains within this defined temperature limit to maintain its effectiveness.


Q: What is the difference between Gliclazide and gliclazide modified release?

The key difference is the rate at which the active ingredient is delivered. The modified-release (MR) tablet is specifically designed for a slow, controlled release of the medicine over several hours. This design benefit often allows for the convenience of once-daily administration, whereas the immediate-release (IR) form may need to be taken twice a day.


Q: Are there any known food interactions besides alcohol for Gliclazide?

Official information for the modified-release formulation indicates that food intake does not affect the absorption of the drug itself. However, having a low-calorie diet or engaging in irregular food intake is documented to increase the overall risk of developing low blood sugar (hypoglycemia) while on Gliclazide.


Q: What does the research say about stopping Gliclazide suddenly?

Official patient information states that Gliclazide should not be stopped suddenly without consultation. Abrupt discontinuation of the medication may potentially cause the patient's diabetes to worsen or result in uncontrolled high blood sugar.


Q: Do patients typically need to adjust their diet when starting Gliclazide?

Yes, regulatory warnings confirm the importance of following dietary advice and maintaining a regular carbohydrate intake when using this medication. Diet is a fundamental and crucial part of the overall management plan for Type 2 Diabetes when Gliclazide is prescribed.

How should Gliclazide be stored and disposed of?

How to Store and Dispose of Gliclazide

Official regulatory documents define specific conditions for storing and disposing of Gliclazide tablets to ensure product integrity and public safety.

Storage Requirements

Gliclazide must be stored at room temperature, specifically below 30°C (86°F), and maintained in a dry place.

Storage Constraint Requirement
Temperature Below 30°C
Protection Protect from light and moisture
Packaging Keep in the original container or blister pack
Child Safety Store out of the sight and reach of children

Disposal Requirements

Unused or expired Gliclazide must not be discarded in wastewater or with household trash. Disposal must be completed according to local requirements for pharmaceutical waste, often involving a return to a local pharmacy take-back program.

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

Available in countries:

Equivalent of Gliclazide found in:

A-Z Index: