GLIPIZIDE AND METFORMIN HYDROCHLORIDE
Clinical safety rating: safe
Alcohol and contrast dye can increase risk of lactic acidosis Can cause lactic acidosis a rare but serious metabolic complication.
Glipizide stimulates insulin secretion from pancreatic beta cells by binding to sulfonylurea receptors and closing ATP-sensitive potassium channels, leading to depolarization and calcium influx. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.
| Metabolism | Glipizide is extensively metabolized in the liver via CYP2C9 to inactive metabolites. Metformin is not metabolized and is excreted unchanged in urine. |
| Excretion | Glipizide: primarily hepatic metabolism (inactive metabolites) with ~97% excreted in urine (mainly metabolites) and ~3% in feces. Metformin: ~90% excreted unchanged in urine via tubular secretion and glomerular filtration (renal). |
| Half-life | Glipizide: terminal t1/2 2–5 hours (prolonged in hepatic impairment). Metformin: plasma t1/2 ~6.2 hours, terminal t1/2 ~17.6 hours (prolonged in renal impairment; clinical accumulation risk). |
| Protein binding | Glipizide: 98–99% bound to albumin. Metformin: negligible (<5%) bound to plasma proteins. |
| Volume of Distribution | Glipizide: Vd ~0.1 L/kg (low, consistent with high protein binding). Metformin: Vd ~1.5 L/kg (large, indicating extensive tissue distribution including hepatic and renal). |
| Bioavailability | Glipizide: ~100% orally (immediate-release); slightly reduced with food. Metformin: ~50–60% orally (immediate-release); reduced to ~30% with extended-release formulations. |
| Onset of Action | Glipizide: peak plasma glucose-lowering effect at 1–3 hours post oral dose. Metformin: onset of glucose lowering within 2 hours, maximal effect within 1–2 weeks. |
| Duration of Action | Glipizide: duration ~12–24 hours (single dose); up to 24 hours with extended-release. Metformin: duration ~12–24 hours (immediate-release requires multiple daily dosing; extended-release once daily). |
| Molecular Weight | Glipizide: 445.5 Da; Metformin: 165.6 Da |
Initial: 2.5 mg glipizide / 250 mg metformin orally twice daily. Titrate gradually based on glycemic control. Maximum: 20 mg glipizide / 2000 mg metformin per day in divided doses.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if eGFR <30 mL/min/1.73 m². If eGFR 30–45 mL/min/1.73 m², do not initiate; discontinue if eGFR falls below 45 mL/min/1.73 m². No dose adjustment needed for eGFR ≥45 mL/min/1.73 m². |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). Avoid use in Child-Pugh class B due to risk of lactic acidosis. No specific adjustment for mild impairment (Child-Pugh A), but use with caution. |
| Pediatric use | Not approved in pediatric patients. Safety and efficacy not established. |
| Geriatric use | Start at the low end of dosing range (2.5 mg/250 mg once or twice daily) due to increased risk of hypoglycemia and renal impairment. Titrate slowly. Monitor renal function frequently. |
| 1st trimester | Glipizide: Limited human data; potential risk of hypoglycemia in neonates if used near term. Metformin: May reduce risk of miscarriage and gestational diabetes complications; consider benefits vs risks. |
| 2nd trimester | Glipizide: Avoid if possible due to neonatal hypoglycemia risk. Metformin: Acceptable alternative to insulin in gestational diabetes; monitor fetal growth. |
| 3rd trimester | Glipizide: Risk of prolonged neonatal hypoglycemia; discontinue before delivery. Metformin: Generally considered safe; may reduce macrosomia risk. |
Clinical note
Alcohol and contrast dye can increase risk of lactic acidosis Can cause lactic acidosis a rare but serious metabolic complication.
| FDA category | Human |
| Placental transfer | Glipizide: Crosses placenta; similar maternal and cord blood levels. Metformin: Crosses placenta; no evidence of teratogenicity. |
■ FDA Black Box Warning
Lactic acidosis associated with metformin. Risk factors include renal impairment, concomitant use of certain drugs (e.g., topiramate), age ≥65 years, radiological studies with contrast, surgery or other procedures, hypoxic states (e.g., acute congestive heart failure), excessive alcohol intake, and hepatic impairment. Symptoms include malaise, myalgia, respiratory distress, increasing somnolence, and non-specific abdominal distress.
| Common Effects | Diarrhea |
| Serious Effects |
Hypersensitivity to glipizide, metformin, or sulfonylureasDiabetic ketoacidosis with or without comaSevere renal impairment (eGFR <30 mL/min/1.73 m²)Acute or chronic metabolic acidosisIntravascular iodinated contrast agents (temporary discontinuation required)
| Precautions | Lactic acidosis risk (see black box warning); hypoglycemia (especially in elderly, debilitated, or malnourished patients, and those with renal or hepatic impairment); cardiovascular considerations (sulfonylureas may increase cardiovascular mortality); hematologic effects (metformin may decrease vitamin B12 levels); acute alcohol consumption; concurrent medications that affect blood glucose; renal function monitoring; surgical procedures; radiologic studies with iodinated contrast. |
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| Breastfeeding | Glipizide: Excreted in breast milk in low amounts; risk of hypoglycemia in infant is minimal but monitor. Metformin: Low concentrations in breast milk; not expected to cause adverse effects in infants. |
| Lactation Rating | L2 (Glipizide) / L2 (Metformin) |
| Teratogenic Risk | First trimester: Glipizide crosses placenta, but studies show low malformation risk. Metformin is considered low risk. Second/third trimester: Glipizide may cause neonatal hypoglycemia; metformin is associated with lower risk of macrosomia and preeclampsia. Overall, limited data for glipizide; metformin preferred. |
| Fetal Monitoring | Maternal: Blood glucose monitoring, HbA1c, renal function, liver enzymes, signs of hypoglycemia/hyperglycemia. Fetal: Ultrasound for growth, anatomy; neonatal monitoring for hypoglycemia, especially with glipizide near term. |
| Fertility Effects | Glipizide: No known adverse effects on fertility. Metformin: May improve ovulation in PCOS; no detrimental impact on fertility. Combination not studied. |
| Food/Dietary | Take with meals to reduce GI side effects. Avoid alcohol: increased risk of lactic acidosis and hypoglycemia. Consistent carbohydrate intake is recommended to prevent blood glucose fluctuations. |
| Clinical Pearls | Glipizide/metformin combines a sulfonylurea (glipizide) that stimulates insulin secretion and a biguanide (metformin) that reduces hepatic glucose output and improves insulin sensitivity. Monitor renal function before initiation and periodically (contraindicated if eGFR <30 mL/min/1.73 m²). Avoid in patients with metabolic acidosis, history of lactic acidosis, or severe hepatic impairment. Titrate slowly to minimize gastrointestinal side effects and hypoglycemia risk. Discontinue if radiocontrast studies are planned; hold metformin on day of procedure and for 48 hours after. Use caution in elderly or debilitated patients due to increased hypoglycemia risk. |
| Patient Advice | Take with meals to reduce gastrointestinal upset and hypoglycemia. · If a dose is missed, take it with the next meal unless it is almost time for the next dose; do not double dose. · Monitor blood glucose regularly and recognize signs of hypoglycemia (shakiness, sweating, confusion) and hyperglycemia (frequent urination, thirst). · Avoid alcohol while taking this medication; it can increase lactic acidosis risk and alter blood sugar. · Report persistent nausea, vomiting, abdominal pain, or unusual drowsiness immediately (possible lactic acidosis). · Store tablets at room temperature, away from moisture and heat. |