Sulfonylurea Pregnancy: Preferably avoid during pregnancy (limited data; animal reproductive toxicity). Insulin is the drug of choice in pregnancy. Contraindicated in breast-feeding.

Gliclazide

Brand names: Diamicron, Diamicron MR

Used in: Diabetes & DKA

Gliclazide is a sulfonylurea used in type 2 diabetes, typically when metformin is insufficient or not tolerated.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 40–320 mg daily (commence 40–80 mg daily, titrate to response)

Route: Oral

Frequency: Once daily; twice daily (with main meals) when higher doses required

Max: 320 mg daily; single dose should not exceed 160 mg

This is for standard (immediate-release, 160 mg tablet) gliclazide. Adjust according to individual blood glucose response. When switching from another oral antidiabetic, start at 40–80 mg and titrate; a treatment-free period of a few days may be needed when switching from a long-half-life sulfonylurea to avoid additive hypoglycaemia. Can be combined with biguanides, alpha-glucosidase inhibitors or insulin. In patients at risk of hypoglycaemia (undernourished/malnourished; poorly compensated endocrine disorders; withdrawal of prolonged/high-dose corticosteroids; severe vascular disease) use the minimum starting dose of 40–80 mg. Take with breakfast to minimise GI effects.

Dose adjustments

Renal

Mild to moderate renal impairment: same dosing regimen as normal renal function with careful monitoring. Severe renal insufficiency: contraindicated (use insulin).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to gliclazide, other sulfonylureas, sulfonamides, or any excipient
Type 1 diabetes
Diabetic pre-coma and coma, diabetic ketoacidosis
Severe renal or hepatic insufficiency (use insulin instead)
Lactation (breast-feeding)
Concomitant treatment with miconazole

Side effects

Hypoglycaemia (most frequent adverse reaction; may be severe/prolonged)
Gastrointestinal disturbances: abdominal pain, nausea, vomiting, dyspepsia, diarrhoea, constipation
Skin reactions: rash, pruritus, urticaria, angioedema; rarely bullous reactions (Stevens-Johnson syndrome, TEN), DRESS
Blood disorders (rare): anaemia, leucopenia, thrombocytopenia, granulocytopenia
Raised hepatic enzymes; hepatitis (isolated reports)

Interactions

Miconazole — contraindicated (increased hypoglycaemic effect)
St John's Wort (Hypericum perforatum) — may affect blood glucose control
Other hypoglycaemic agents / combined antidiabetic therapy increase hypoglycaemia risk
Alcohol increases hypoglycaemia risk

Clinical monograph

How it works

Gliclazide stimulates insulin release from pancreatic beta cells by closing ATP-sensitive potassium channels; it therefore requires residual beta-cell function.

Prescribing in practice

Unlike metformin it can cause hypoglycaemia and modest weight gain — counsel on recognition and treatment of hypoglycaemia.
Use caution and lower doses in older patients and in renal or hepatic impairment, where hypoglycaemia risk rises.
Take with meals; the modified-release form is given once daily.

Monitoring

Monitor HbA1c for response and review for hypoglycaemia; reassess in renal or hepatic impairment.

Counselling the patient

It can cause low blood sugar — carry a fast-acting sugar and know the warning signs.
Take it with food and do not skip meals.
Be cautious with alcohol, which can worsen hypoglycaemia.

Evidence & guidelines

Sulfonylureas are an option to intensify treatment in type 2 diabetes per NICE NG28, balancing efficacy against hypoglycaemia and weight gain.

Reference: NICE NG28; Scottish Medicines Consortium; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways