MEZLIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MEZLIN (MEZLIN).
Mezlocillin is a ureidopenicillin that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), specifically inhibiting transpeptidase activity, leading to cell lysis.
| Metabolism | Primarily excreted unchanged in urine via glomerular filtration and tubular secretion; partially metabolized hepatically to benzylpenicilloyl derivatives. |
| Excretion | Renal (70-80% unchanged via glomerular filtration and tubular secretion); biliary (approximately 2-3%); fecal (minor). |
| Half-life | Terminal elimination half-life is 0.7-1.2 hours in healthy adults; prolonged to 2-5 hours in renal impairment (CrCl <20 mL/min) and up to 10-20 hours in ESRD. |
| Protein binding | 16-50% bound primarily to albumin. |
| Volume of Distribution | 0.2-0.3 L/kg; distributes well into extracellular fluid, bile, and pleural fluid; limited CSF penetration. |
| Bioavailability | IM: approximately 80% absorbed; IV: 100%. |
| Onset of Action | IV: Immediate peak concentrations; IM: 30-60 minutes for therapeutic levels. |
| Duration of Action | Approximately 4-6 hours for susceptible bacteria; requires frequent dosing (q4-6h) due to short half-life. |
| Molecular Weight | 539.6 |
3-4 g intravenously every 4-6 hours; maximum 24 g/day.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-50 mL/min: 3 g every 6 hours; CrCl 10-29 mL/min: 3 g every 8 hours; CrCl <10 mL/min: 2 g every 12 hours. |
| Liver impairment | No specific adjustment recommended; caution in severe hepatic impairment. |
| Pediatric use | Infants >7 days and children: 200-300 mg/kg/day intravenously divided every 4-6 hours; maximum 24 g/day. |
| Geriatric use | Start at lower end of dosing range; monitor renal function and adjust based on creatinine clearance. |
| 1st trimester | Generally avoided unless clearly needed; first trimester organogenesis risk unknown but theoretical based on penicillin class safety. Limited human data, but penicillin antibiotics are generally considered low risk; weigh benefit. |
| 2nd trimester | Use if clearly needed; penicillin antibiotics are generally considered safe in second trimester; monitor for maternal adverse effects. |
| 3rd trimester | Use if clearly needed; penicillin antibiotics are generally safe; consider potential for alteration of gut flora in neonate if given near term. |
Clinical note
Comprehensive clinical and safety monograph for MEZLIN (MEZLIN).
| Placental transfer | Crosses placenta; achieves fetal serum concentrations approximately 20-50% of maternal levels. Sufficient to treat fetal infections. |
| Breastfeeding | Excreted into breast milk in low concentrations; generally considered compatible with breastfeeding. Monitor infant for potential diarrhea, candidiasis, or allergic reaction. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to mezlocillin or any penicillinHypersensitivity to cephalosporins (potential cross-sensitivity)Severe immediate allergic reaction (e.g., anaphylaxis) to beta-lactam antibiotics
| Precautions | Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported, Clostridium difficile-associated diarrhea (CDAD) may occur, Renal impairment requires dosage adjustment, Prolonged use may result in superinfection, May cause neurotoxicity with high doses or renal failure |
| Food/Dietary | No significant food interactions; however, if taken orally (though MEZLIN is typically IV), avoid alcohol as it may cause a disulfiram-like reaction with some penicillins. Maintain adequate hydration. |
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| Lactation Rating | L1 (Safe) |
| Teratogenic Risk | Mezlin (mezlocillin) is a penicillin-class antibiotic. Available human data are limited, but penicillins are generally considered low risk in pregnancy. Animal studies have not shown teratogenicity. First trimester: No evidence of fetal harm, but data are insufficient to rule out risk. Second and third trimesters: Considered safe when clinically indicated. Avoid use only if hypersensitivity to penicillins exists. |
| Fetal Monitoring | Monitor maternal renal and hepatic function periodically. Observe for signs of hypersensitivity reactions. In prolonged therapy, monitor for superinfection. No specific fetal monitoring required, but assess for adverse effects if given near term. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies have not reported reproductive toxicity at therapeutic doses. |
| Clinical Pearls | MEZLIN (mezlocillin) is a ureidopenicillin with extended gram-negative coverage, including Pseudomonas. Use with caution in patients with bleeding disorders due to potential hypoprothrombinemia. Adjust dose in renal impairment; creatinine clearance <30 mL/min requires extended dosing interval. Administer IV slowly over 3-5 minutes to reduce vein irritation. Synergistic with aminoglycosides; avoid mixing same IV line. |
| Patient Advice | Take exactly as prescribed; complete the full course even if you feel better. · Report any signs of allergic reaction: rash, itching, difficulty breathing, swelling of lips/face. · Notify your doctor if you experience unusual bleeding or bruising, or if you have diarrhea that is watery or bloody. · This medication is given intravenously; you may have discomfort at the injection site. |