UTIMOX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for UTIMOX (UTIMOX).
Amoxicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation and autolysin activation. Clavulanate is a beta-lactamase inhibitor that irreversibly binds to and inactivates beta-lactamases, preventing hydrolysis of amoxicillin.
| Metabolism | Amoxicillin is partially metabolized to amoxicilloic acid via renal excretion; Clavulanate is extensively metabolized to 2,5-dihydro-4-(2-hydroxyethyl)-5-oxo-1H-pyrrole-3-carboxylic acid and 1-amino-4-hydroxy-butan-2-one. Both are primarily eliminated renally. |
| Excretion | Primarily renal (85-90% as unchanged drug via glomerular filtration and tubular secretion); biliary/fecal excretion accounts for less than 10%. |
| Half-life | Terminal elimination half-life: 1.0-1.5 hours in adults with normal renal function; prolonged to 3-5 hours in moderate renal impairment (CrCl 30-50 mL/min) and up to 8-12 hours in severe impairment (CrCl <30 mL/min). |
| Protein binding | Approximately 20% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 0.3-0.4 L/kg; moderate distribution into extracellular fluid, with good penetration into most tissues including bone, synovial fluid, and bile. |
| Bioavailability | Oral: 70-80% (food delays absorption but does not affect extent; avoid high-fat meals). |
| Onset of Action | Oral: 30-60 minutes after oral administration; IV: Immediate (within minutes) upon completion of infusion. |
| Duration of Action | Duration approximately 6-8 hours; dosing interval adjusted to 12-24 hours in renal impairment to maintain therapeutic levels. |
| Molecular Weight | 253.3 |
For UTIMOX (amoxicillin/clavulanate), typical adult dose is 875 mg/125 mg orally every 12 hours or 500 mg/125 mg orally every 8 hours, depending on infection severity.
| Dosage form | CAPSULE |
| Renal impairment | For GFR 10-30 mL/min: 500 mg/125 mg every 12 hours. GFR <10 mL/min: 500 mg/125 mg every 24 hours. Hemodialysis: 500 mg/125 mg during dialysis and then every 24 hours. |
| Liver impairment | No specific dose adjustment required for Child-Pugh A or B; caution in severe hepatic impairment (Child-Pugh C) with monitoring for adverse effects. |
| Pediatric use | Weight-based dosing: For children 40 kg or more, use adult dosing; for children <40 kg, 25-45 mg/kg/day of amoxicillin component in divided doses every 12 hours, based on infection severity. Common regimen: 20-40 mg/kg/day amoxicillin in 3 divided doses for more serious infections. |
| Geriatric use | Elderly patients: Normal dosing unless renal impairment; monitor renal function and adjust dose accordingly (per renal adjustment). Increased risk of Clostridioides difficile infection and adverse effects due to age-related renal decline. |
| 1st trimester | Avoid due to possible interference with folic acid metabolism and potential teratogenicity (neural tube defects). |
| 2nd trimester | Use only if benefit outweighs risk; consider alternative sulfonamides with lower risk. |
| 3rd trimester | Avoid due to risk of kernicterus in the newborn from bilirubin displacement. |
Clinical note
Comprehensive clinical and safety monograph for UTIMOX (UTIMOX).
| Placental transfer | Sulfamethoxazole and trimethoprim cross the placenta; peak concentrations in fetal serum reach about 50-60% of maternal levels. |
| Breastfeeding | Sulfamethoxazole is excreted into breast milk in small amounts. In infants with glucose-6-phosphate dehydrogenase deficiency or hyperbilirubinemia, use caution. The American Academy of Pediatrics considers sulfamethoxazole/trimethoprim compatible with breastfeeding, but avoid in ill or premature infants. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Hypersensitivity to sulfonamides or trimethoprimMegaloblastic anemia due to folate deficiencyPregnancy (especially first trimester and near term)Breastfeeding in infants with G6PD deficiency or hyperbilirubinemia
| Precautions | Serious hypersensitivity reactions (anaphylaxis), severe cutaneous adverse reactions (SCARs), Clostridioides difficile-associated diarrhea, hepatotoxicity, development of drug-resistant bacteria, use in patients with mononucleosis (risk of rash), renal impairment (dose adjustment), and prolonged therapy may cause bacterial or fungal superinfection. |
| Food/Dietary | Take with food to enhance absorption and reduce gastrointestinal intolerance. Avoid alcohol as it may cause disulfiram-like reaction with cephalosporins. |
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| Lactation Rating | L3 (Limited Data) - Probably Compatible with caution in G6PD-deficient or jaundiced infants. |
| Teratogenic Risk | UTIMOX (amoxicillin) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and adequate studies in pregnant women have not shown teratogenic effects. However, penicillins cross the placenta. First trimester: No increased risk of major malformations. Second/third trimester: No known fetal harm; used for infections like UTI and GBS prophylaxis. |
| Fetal Monitoring | Monitor maternal renal function (amoxicillin primarily excreted renally) and signs of allergic reaction. No specific fetal monitoring required. In prolonged therapy, consider monitoring infant for diarrhea or candidiasis. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. Amoxicillin does not impair reproductive function. |
| Clinical Pearls | UTIMOX is a combination of cefuroxime and clavulanic acid; ensure renal dose adjustment for CrCl <30 mL/min. Monitor for hypersensitivity reactions, especially in penicillin-allergic patients. Thrombophlebitis risk with IV administration; rotate infusion sites. |
| Patient Advice | Complete the full course even if symptoms improve. · Report any signs of allergy (rash, itching, swelling) or severe diarrhea. · Take with food to reduce GI upset. · Avoid alcohol during treatment and for 48 hours after completion. · Use effective contraception if applicable; cefuroxime may reduce oral contraceptive efficacy. |