CYCLAPEN-W
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYCLAPEN-W (CYCLAPEN-W).
Cyclacillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death. It has a similar spectrum to ampicillin but with increased acid stability and oral absorption.
| Metabolism | Cyclacillin is partially metabolized in the liver to penicilloic acid and other metabolites. Approximately 20-40% of the dose is excreted unchanged in urine via glomerular filtration and tubular secretion. |
| Excretion | Primarily renal (90-100% unchanged via glomerular filtration and tubular secretion); minor biliary/fecal elimination (<10%). |
| Half-life | 0.5-1 hour in adults with normal renal function; prolonged to 2-6 hours in renal impairment. |
| Protein binding | Approximately 80% bound; primarily to serum albumin. |
| Volume of Distribution | 0.3-0.4 L/kg; indicates distribution primarily into extracellular fluid. |
| Bioavailability | Oral: 60-70% (decreased by food); IM: nearly 100%. |
| Onset of Action | Oral: 30-60 minutes; IM: 15-30 minutes; IV: immediate (within minutes). |
| Duration of Action | 4-6 hours for oral/IM; clinical effect lasts 6-8 hours due to post-antibiotic effect. |
250-500 mg orally every 6 hours for mild to moderate infections; 500 mg orally every 6 hours for severe infections.
| Dosage form | TABLET |
| Renal impairment | CrCl 10-50 mL/min: 250-500 mg every 8-12 hours; CrCl <10 mL/min: 250-500 mg every 12-18 hours. |
| Liver impairment | No adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Use with caution in severe impairment (Child-Pugh C) due to risk of encephalopathy. |
| Pediatric use | Children >1 month: 25-50 mg/kg/day orally divided every 6 hours. Maximum 2 g/day. |
| Geriatric use | No specific dose adjustment, but monitor renal function. Use lowest effective dose due to age-related renal decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYCLAPEN-W (CYCLAPEN-W).
| Breastfeeding | Penicillin V is excreted into breast milk in low concentrations (<5% of maternal dose). The M/P ratio is approximately 0.5. Considered compatible with breastfeeding; monitor infant for potential gastrointestinal disturbances or allergic reactions. |
| Teratogenic Risk | Penicillin V (Cyclapen-W) is generally considered low risk for teratogenicity across all trimesters. Animal studies have not shown fetal harm, and human data do not indicate an increased risk of major malformations. However, use only if clearly needed, especially during the first trimester. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Hypersensitivity to cyclacillin, penicillins, or any component of the formulation.","History of immediate hypersensitivity reaction (e.g., anaphylaxis) to any beta-lactam antibiotic (e.g., cephalosporins, carbapenems)."]
| Precautions | ["Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported.","Prolonged use may result in overgrowth of nonsusceptible organisms, including Clostridium difficile-associated diarrhea.","Use with caution in patients with renal impairment; dose adjustment may be necessary.","Use in patients with mononucleosis may increase risk of maculopapular rash."] |
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| Fetal Monitoring |
| No specific fetal monitoring required. Standard clinical monitoring for maternal allergic reactions, gastrointestinal side effects, and signs of superinfection. In neonates, monitor for diarrhea, rash, or candidiasis. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies have not demonstrated impaired fertility. |