Formet XR | 500

✔️ Dosage & Administration

Immediate-Release Metformin:

Adults: Start 500 mg twice daily or 850 mg once daily with meals. Increase by 500 mg weekly or 850 mg every 2 weeks up to 2000 mg/day (divided doses). Maximum tolerated: 2550 mg/day in divided doses.

Children: Start 500 mg twice daily, increase by 500 mg weekly, max 2000 mg/day.

Extended-Release (Formet XR):

Adults: Start 500 mg once daily with evening meal, increase weekly by 500 mg up to 2000 mg/day, or 1000 mg twice daily.

Children: Not studied.

Renal impairment: Avoid if eGFR <30 mL/min/1.73 m²; assess risk if eGFR <45 mL/min/1.73 m².

Important: Swallow XR tablets whole; do not crush, cut, or chew.

✔️ Side Effects

Gastrointestinal: nausea, vomiting, diarrhea, abdominal pain, loss of appetite (usually during therapy initiation)

Very rare:

• Lactic acidosis
• Vitamin B12 deficiency leading to megaloblastic anemia
• Liver function abnormalities, hepatitis
• Skin reactions: erythema, pruritus, urticaria

Others:

• Taste disturbances
• Peripheral neuropathy in B12 deficiency

✔️ Interaction

Furosemide: No chronic interaction data.

Nifedipine: May enhance Formet XR absorption.

Cationic drugs (Amiloride, Digoxin, Morphine, etc.): Potential renal tubular interactions.

Other drugs affecting glucose: Thiazides, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid.

✔️ Contraindications

• Hypersensitivity to metformin or excipients
• Acute metabolic acidosis (including lactic acidosis or diabetic ketoacidosis)
• Severe renal failure (GFR <30 mL/min)
• Acute conditions altering renal function (dehydration, severe infection, shock)
• Conditions causing tissue hypoxia (cardiac/respiratory failure, recent MI, hepatic insufficiency, acute alcohol intoxication)

✔️ Pregnancy & Lactation

Pregnancy: Prefer insulin to maintain normal glucose and reduce fetal risk; avoid metformin.

Breastfeeding: Metformin passes into milk; limited data, adverse effects not observed in infants. Use caution.

✔️ Precautions & Warnings

• Monitor renal function regularly; adjust dose in elderly or those with renal impairment.
• Stop 2–3 days before surgery or contrast studies, resume only after renal function stabilizes.
• Annual Vitamin B12 assessment recommended during prolonged therapy.
• Risk of hypoglycemia when combined with insulin or insulin secretagogues.
• Dose adjustment may be needed during cimetidine therapy or with anticoagulants.
• Special Populations:
• Elderly: Assess renal function before and during treatment.
• Children 10–12 years: Use caution; monitor growth and puberty.

✔️ Storage:

Keep below 30°C, protected from light and moisture

Keep out of reach of children