METRETON
Clinical safety rating: caution
Comprehensive clinical and safety monograph for METRETON (METRETON).
Antihistamine and mast cell stabilizer. Competitively inhibits histamine at H1 receptors and prevents release of histamine and other mediators from mast cells.
| Metabolism | Not extensively metabolized; primarily excreted unchanged in urine. |
| Excretion | Renal (80-90% as unchanged drug and metabolites), biliary/fecal (10-20%) |
| Half-life | Terminal elimination half-life is 24-36 hours; increased in renal impairment (up to 60 hours in anuria) |
| Protein binding | 75-85% bound to albumin and alpha-1-acid glycoprotein |
| Volume of Distribution | 0.5-1.0 L/kg; indicates moderate tissue distribution |
| Bioavailability | Oral: 50-70% (first-pass metabolism); Intramuscular: 80-100% |
| Onset of Action | Oral: 30-60 minutes; Intramuscular: 15-30 minutes; Intravenous: immediate |
| Duration of Action | Oral: 8-12 hours; Intramuscular: 6-8 hours; Intravenous: 4-6 hours; duration prolonged in hepatic impairment |
| Molecular Weight | 358.43 |
1-2 mg/kg intramuscularly or intravenously every 6-8 hours as needed; maximum 100 mg per dose.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | CrCl 10-50 mL/min: administer every 12 hours; CrCl <10 mL/min: administer every 12-18 hours or consider dose reduction by 50%. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B: reduce dose by 50%; Class C: avoid use or reduce dose by 75%. |
| Pediatric use | 0.5-1 mg/kg intramuscularly or intravenously every 6-8 hours; maximum 25 mg per dose for children <40 kg. |
| Geriatric use | Start at lower end of dosing range (e.g., 0.5-1 mg/kg) with extended intervals (every 8-12 hours) due to decreased renal function and increased sensitivity. |
| 1st trimester | Avoid. Potential teratogenic effects reported with corticosteroids; increased risk of cleft palate if used in first trimester. |
| 2nd trimester | Use only if clearly needed. May cause fetal adrenal suppression; monitor fetal growth restriction. |
| 3rd trimester | Use only if clearly needed. Prolonged use may cause neonatal adrenal suppression; avoid high doses near term. |
Clinical note
Comprehensive clinical and safety monograph for METRETON (METRETON).
| Placental transfer | Crosses placenta; metabolized to active form prednisolone; placental 11β-HSD2 partially inactivates drug. |
| Breastfeeding | Enters breast milk in small amounts; theoretical risk of adrenal suppression in infant. Use lowest effective dose for shortest duration. |
■ FDA Black Box Warning
None
| Serious Effects |
Systemic fungal infectionsHypersensitivity to any component
| Precautions | Do not inject; for ophthalmic use only., May cause transient burning or stinging., Use with caution in patients with narrow-angle glaucoma. |
| Food/Dietary | Avoid excessive alcohol intake (increases risk of lactic acidosis). No specific food restrictions, but consistent carbohydrate intake is recommended to prevent hypoglycemia. Grapefruit may increase metformin levels (use caution). |
| Clinical Pearls |
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| Lactation Rating |
| L3 (Moderately Safe) |
| Teratogenic Risk | Pregnancy Category C: Fetal risk cannot be ruled out. First trimester: Increased risk of cleft palate and cardiac malformations due to corticosteroid component (prednisolone). Second and third trimesters: Potential for intrauterine growth restriction, adrenal suppression in neonate. Avoid use unless benefit outweighs risk. |
| Fetal Monitoring | Maternal: Blood pressure, blood glucose, signs of infection, weight gain. Fetal: Ultrasound for growth restriction if used long-term in second/third trimester; neonatal assessment for adrenal suppression if used near term. |
| Fertility Effects | No known direct effect on fertility. Corticosteroids may cause menstrual irregularities or ovulatory dysfunction at high doses, potentially impacting conception. Antihistamines are not associated with fertility impairment. |
| METRETON is a fixed-dose combination of metformin and sitagliptin. Use with caution in patients with renal impairment (check eGFR before initiation; contraindicated if eGFR <30 mL/min/1.73 m²). Monitor for lactic acidosis, especially in hypoxic states or hepatic impairment. Discontinue temporarily before iodinated contrast imaging and for surgery. Assess for pancreatitis (discontinue if suspected). Do not use in type 1 diabetes or diabetic ketoacidosis. Dose adjustment of sitagliptin needed if eGFR 30-45 mL/min/1.73 m² (50 mg daily). |
| Patient Advice | Take with meals to reduce gastrointestinal side effects. · Do not drink excessive alcohol while taking this medication. · Monitor for symptoms of lactic acidosis (unusual tiredness, muscle pain, trouble breathing, stomach pain) and pancreatitis (severe stomach pain, nausea, vomiting). · Inform your doctor if you become pregnant or plan to breastfeed. · Report any signs of allergic reaction (rash, hives, swelling of face/lips/throat) immediately. · Maintain adequate fluid intake, especially during illness or in hot weather. · Do not skip meals or drastically reduce carbohydrate intake without consulting your provider. |