Metformin ER

GLUCOPHAGE XR

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Pronunciation: met-FOR-min

Metformin ER ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Metformin ER ballicule

Metformin ER GLUCOPHAGE mascot mnemonic cartoon — Visual mnemonic: Metformin ER mascot
**“Mr Met formin’ Glucose Fudge”**

What it isExtended-release biguanide (GLUCOPHAGE XR, 2000) that inhibits complex I and suppresses hepatic glucose production; type 2 diabetes.

Why this oneTaken once daily with the evening meal, slower delivery reduces GI peaks and can preserve therapy after immediate-release intolerance; ghost tablet in stool is expected.

What limits itRenal accumulation can precipitate lactic acidosis; monitor kidney function. GI symptoms and long-term B12 depletion still occur.

Metformin ER molecular structure (skeletal formula) — Molecular structure: Metformin ER

Metformin ER prescription history

Animated chart of estimated U.S. prescriptions per year, Diabetes meds (1923–2026). Metformin ER enters in 1995 (estimated).

FDA-approved for

type 2 diabetes (2000)

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger2 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryB

Defining liabilityGI intolerance and vitamin B12 deficiency; severe renal/hypoxic illness can precipitate lactic acidosis.

FDA label

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BOXED WARNING Lactic acidosis: postmarketing metformin-associated lactic acidosis has caused death, hypothermia, hypotension, resistant bradyarrhythmias; risk rises with renal impairment, certain drugs, age ≥65, contrast, surgery, hypoxia, excess alcohol, hepatic impairment — discontinue and hemodialyze if suspected.

FDA dosing	Population	Start	Target	Max
Type 2 diabetes mellitus (adjunct to diet/exercise)	Adults	500 mg QD with evening meal	500–2000 mg/day	2000 mg QD (or 1000 mg BID)

Titration Increase in 500 mg increments at weekly intervals

Renal Contraindicated if eGFR <30 mL/min/1.73m²; initiation not recommended if eGFR 30–45; reassess risk/benefit if eGFR falls below 45; discontinue if below 30

Hepatic Avoid use in patients with hepatic impairment (risk of lactic acidosis)

Instructions

Swallow whole with evening meal; never crush, cut, or chew
Discontinue at time of or prior to iodinated contrast imaging in at-risk patients; re-evaluate eGFR after 48 h
May switch from IR metformin to same total daily dose once daily, up to 2000 mg

Available strengths

ER tab 500, 750, 1000 mg

Contraindications

Severe renal impairment (eGFR below 30 mL/min/1.73 m²)
Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma

Cautions

Lactic acidosis (see Boxed Warning)
Vitamin B12 deficiency — monitor hematologic parameters annually, B12 every 2–3 years
Hypoglycemia when combined with insulin or insulin secretagogues — may need lower dose

Adverse reactions

Diarrhea
Nausea/vomiting
Flatulence
Asthenia
Indigestion
Abdominal discomfort
Headache

Pregnancy Limited data insufficient for risk; published data have not shown clear association with birth defects/miscarriage; poorly controlled diabetes carries maternal/fetal risk

Lactation Metformin present in human milk (infant dose ~0.11–1% maternal); insufficient data on effects; weigh benefits vs. risk