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Gliclazide is a sulfonylurea that has been classified as second generation anti-diabetic drug. It is an oral anti-diabetic that is best taken with meals. It has antioxidant effects and may have some blood thinning effects.


Chemical nature

Gliclazide is known by its systemic name of N-(hexahydrocyclopenta[c]pyrrol-2(1H)-ylcarbamoyl)-4-methylbenzenesulfonamide and its molecular formula, C15H21N3O3S. It is deadly at 3 grams per kilogram body weight.

Gliclazide's mechanism of action is similar to glibenclamide. It closes channels that allow potassium ions to enter the beta cells. The lowered levels of intracellular potassium will allow calcium ions to enter. These ions will bind and eventually activate calmodulin and release insulin.

Uses and common dosages

Gliclazide is prescribed for the treatment of diabetes mellitus, especially when it cannot be controlled by dietary management or when treatment with insulin in not advisable. The drug must be taken with food or 20 minutes before meals and a full glass of water at the same time each day.

Doctors may give 40 to 80 milligrams of gliclazide daily. This can be gradually increased to 320 milligrams a day to achieve the desired effect. Doses that are greater than 160 milligrams a day may be given in two divided doses. There is no fixed dosage regimen for any anti-diabetic drug as it will depend on the blood glucose during dose titration and maintenance.

Modified release tablets may be given initially at 30 milligrams once a day and gradually increased to 120 milligrams within 24 hours. it must not be crushed, cut or chewed.

The drug will exert its effect 1 to 2 hours after ingestion. Its peak action is achieved bt 4 to 6 hours. Its effects last for 12 hours.

Side effects

Some undesirable effects that may be associated with the use of gliclazide are:

  • Weight gain is a possibility but can be controlled by diet and exercise.
  • Blurred vision, high blood pressure, and vasculitis usually appear at the start of treatment.
  • Hypoglycemia that manifests as dizziness, weakness, drowsiness, headache, sweating, nervousness, shaking, tingling of extremities, hunger, and fast heartbeat may occur.
  • Gastrointestinal disturbances which can appear as nausea, stomach upset, or diarrhea may happen as the body adjusts to the medication.
  • Skin rashes, itching, easy bruising or bleeding, fever, and trembling or chills must be reported IMMEDIATELY to a physician.

The doctor may require patients to check their blood sugar regularly when taking this medication.

Precautions and contraindications

Gliclazide must NOT be given to the following patients:

  • Aged 12 and below
  • Has type 1 diabetes
  • Has developed hypersensitivity to sulfonylurea
  • Has a tendency to develop diabetic ketoacidosis
  • Has severe renal or hepatic failure
  • Pregnant and breastfeeding mothers
  • Has porphyrias

Physicians may adjust the usual recommended dose in patients with the following conditions:

  • Aged 65 and above
  • Has a scheduled surgery or major dental procedure
  • Has an infection or severe trauma
  • Has metabolic problems (i.e. thyroid problems, glucose-6-phosphate dehydrogenase deficiency)
  • Malnourished

The prescriber must be informed when gliclazide might possibly be used with these medications:

  • Danazol,chlorpromazine, glucocorticoids, progestogens, or beta-blockers lowers the effect of gliclazide.
  • Phenylbutazone, alcohol, fluconazole, and ACE inhibitors increases its hyoglycemic effects.
  • Alcohol may cause nausea, giddiness, rapid heart rate and flushing.
  • Beta-blockers such as propranolol may hide the signs of low blood sugar and prevent recovery of normal glucose levels.

Gliclazide might cause photosensitivity so protective clothing and sunscreen is advisable.


Gliclazide may be readily available in pharmacies all over the Philippines as a tablet or as modified release tablets. Ordinary tablets are available at 80 milligrams while modified release versions have 30 milligrams. It can be purchased but only with a doctor's prescription. There are no formulations currently available that is in combination with this drug. Popular brands include Diamicron ®, Dianorm ®, and Gluconil ®.