CYCLACILLIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYCLACILLIN (CYCLACILLIN).
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.
| Metabolism | Cyclacillin is primarily renally excreted unchanged; minimal hepatic metabolism occurs. |
| Excretion | Primarily renal (90%) as unchanged drug via glomerular filtration and tubular secretion; negligible biliary/fecal elimination (<5%). |
| Half-life | 0.5–1 hour in adults with normal renal function; prolonged to 10–15 hours in anuria. |
| Protein binding | 25% bound to serum albumin. |
| Volume of Distribution | 0.3–0.4 L/kg; distributes into extracellular fluid and inflamed tissues. |
| Bioavailability | Oral: 50–60% (dose-dependent, reduced by food). |
| Onset of Action | Oral: 1–2 hours; IM: 30–60 minutes. |
| Duration of Action | 4–6 hours; renal impairment extends duration. |
| Molecular Weight | 319.37 |
250-500 mg orally every 6 hours.
| Dosage form | TABLET |
| Renal impairment | CrCl >50 mL/min: 250-500 mg every 6 hours; CrCl 10-50 mL/min: 250-500 mg every 12 hours; CrCl <10 mL/min: 250-500 mg every 24 hours. |
| Liver impairment | No adjustment required. Hepatic impairment does not significantly affect cyclacillin pharmacokinetics. |
| Pediatric use | Children >20 kg: 250-500 mg orally every 6 hours; Children <20 kg: 12.5-25 mg/kg/day divided every 6 hours. |
| Geriatric use | No specific adjustment; monitor renal function and adjust based on creatinine clearance as per adult renal guidelines. |
| 1st trimester | Generally considered safe; animal studies do not indicate fetal risk. |
| 2nd trimester | Safe; no known teratogenic effects. |
| 3rd trimester | Safe; use only if clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for CYCLACILLIN (CYCLACILLIN).
| Placental transfer | Crosses placenta; reaches fetal serum concentrations approximately 10% of maternal serum levels. |
| Breastfeeding | Excreted into breast milk in low amounts; unlikely to cause adverse effects in nursing infants. |
| Lactation Rating | L1 (Safe) |
■ FDA Black Box Warning
No FDA boxed warning exists for cyclacillin.
| Serious Effects |
Hypersensitivity to cyclacillin or other penicillins
| Precautions | Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported., Prolonged use may result in overgrowth of nonsusceptible organisms., Use cautiously in patients with renal impairment. |
| Food/Dietary | No significant food interactions; however, high-fat meals may delay absorption. Avoid acidic drinks like citrus juices which may reduce stability. |
| Clinical Pearls |
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| Teratogenic Risk | No evidence of teratogenicity in animal studies; limited human data. Pregnancy category B. No known fetal risk in any trimester. |
| Fetal Monitoring | No specific monitoring required beyond standard pregnancy care. |
| Fertility Effects | No known adverse effects on fertility. |
| Cyclacillin is a penicillin-class antibiotic with activity similar to ampicillin but with more rapid and complete oral absorption. It is primarily used for respiratory and urinary tract infections caused by susceptible organisms. Note that it is inactivated by beta-lactamases and should not be used for beta-lactamase-producing pathogens. Renal dose adjustment required in severe impairment. |
| Patient Advice | Take exactly as prescribed; complete the full course even if you feel better. · Do not share this medication with others. · Take with or without food; but avoid acidic beverages like fruit juice. · Contact your doctor if you develop severe diarrhea, rash, or difficulty breathing. · Report any signs of allergic reaction (hives, swelling, anaphylaxis) immediately. |