COACTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for COACTIN (COACTIN).
Coactin (mecillinam) is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding protein 2 (PBP2) in gram-negative bacteria, leading to the formation of spheroplasts and cell lysis.
| Metabolism | Coactin is not significantly metabolized; it is excreted largely unchanged in the urine via glomerular filtration and tubular secretion. |
| Excretion | Renal: approximately 70-80% as unchanged drug via glomerular filtration and tubular secretion; biliary/fecal: less than 10% as metabolites and unchanged drug. |
| Half-life | Terminal elimination half-life: 1.0-1.5 hours in adults with normal renal function; prolonged to 2-6 hours in renal impairment; clinically requires frequent dosing or dose adjustment in renal failure. |
| Protein binding | Approximately 30-40% bound to serum albumin; low binding reduces displacement interactions. |
| Volume of Distribution | 0.2-0.4 L/kg; indicates limited extravascular distribution, mainly in extracellular fluid; clinically relevant for dosing in edema or ascites. |
| Bioavailability | Intravenous: 100%; intramuscular: approximately 70-80%; oral: negligible (<5%) due to acid instability; not used orally. |
| Onset of Action | Intravenous: within minutes; intramuscular: 30-60 minutes; oral: not administered orally due to poor bioavailability. |
| Duration of Action | Intravenous: 4-6 hours for susceptible organisms; dosing interval typically 4-6 hours; prolonged in renal impairment. |
400 mg orally every 6-8 hours with a full glass of water.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-50 mL/min: 400 mg every 8-12 hours; CrCl 10-29 mL/min: 400 mg every 12-24 hours; CrCl <10 mL/min: 400 mg every 24 hours. |
| Liver impairment | No adjustment required for mild to moderate hepatic impairment. Contraindicated in severe hepatic impairment (Child-Pugh class C). |
| Pediatric use | For children >6 months: 10-15 mg/kg every 6 hours, not to exceed 400 mg per dose. |
| Geriatric use | Start at lower end of dosing range; monitor renal function and adjust based on CrCl. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for COACTIN (COACTIN).
| Breastfeeding | Amdinocillin is excreted into human breast milk in small amounts. The M/P ratio has not been specifically reported for amdinocillin; however, for penicillins, M/P ratios are typically <0.1. Concentrations in milk are low and unlikely to cause adverse effects in the nursing infant. Considered compatible with breastfeeding, but monitor for infant diarrhea, rash, or sensitization. |
| Teratogenic Risk | COACTIN (amdinocillin) is a penicillin-class antibiotic. FDA pregnancy category B: Animal reproduction studies have not demonstrated fetal risk, but there are no adequate and well-controlled studies in pregnant women. First trimester: Low risk based on animal data; human data limited. Second and third trimesters: Considered safe for use when indicated, as penicillins are generally regarded as low risk. No evidence of teratogenicity in clinical use. |
■ FDA Black Box Warning
None
| Serious Effects |
Absolute: Known hypersensitivity to mecillinam, other beta-lactams, or any component of the formulation. Relative: History of severe allergic reaction to penicillin or cephalosporins; severe renal impairment (CrCl <10 mL/min) unless dose adjusted.
| Precautions | Hypersensitivity reactions including anaphylaxis; cross-allergenicity with other beta-lactams; use with caution in patients with renal impairment; superinfection with prolonged use; pseudomembranous colitis; seizure potential in high doses or with renal insufficiency. |
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| Fetal Monitoring | Maternal: Monitor for signs of hypersensitivity reactions, gastrointestinal disturbance, and Clostridioides difficile diarrhea. Fetal/Neonatal: No specific fetal monitoring required; routine antenatal care applies. Observe neonate for potential allergic reactions or gastrointestinal effects if given near delivery. |
| Fertility Effects | No known adverse effects of amdinocillin on male or female fertility in animal studies or clinical reports. Penicillins are not associated with fertility impairment. No specific data on amdinocillin; however, class effect suggests no impact. |