Stability of Reconstituted Cloxacillin Solution
Reconstituted cloxacillin solution should be stored refrigerated at 4°C and used within 3 days for intravenous preparations, or within 7 days for oral suspensions stored under refrigeration.
Storage Temperature Requirements
Refrigeration at 4°C is essential for maintaining cloxacillin stability. The evidence consistently demonstrates that cloxacillin degrades rapidly at room temperature but maintains acceptable potency when refrigerated 1. For parenteral formulations used in outpatient settings, cloxacillin solutions stored at 5°C maintain stability for approximately 3 days, while storage at 25°C (room temperature) results in degradation within just 1 day 1.
Temperature-Specific Stability Data
- Room temperature (20-25°C): Cloxacillin solutions degrade rapidly, with only 1 day of acceptable stability 1
- Refrigerated (4-5°C): Solutions remain stable for 3-7 days depending on formulation 1, 2
- Frozen (-20°C): Extended stability up to 21 days has been demonstrated for oral suspensions 2
Formulation-Specific Considerations
The stability of cloxacillin varies significantly based on the preparation method and vehicle used:
For oral suspensions repackaged in unit-dose syringes, degradation follows zero-order kinetics at refrigerated temperatures, with acceptable stability limited to 7 days at ambient conditions, 10 days refrigerated, and up to 21 days when frozen at -20°C 2. Importantly, repackaging into polypropylene syringes accelerates degradation compared to storage in the manufacturer's original container 2.
For oily suspension formulations, the preparation method dramatically affects stability. When lyophilized sodium cloxacillin is used, approximately 10% degradation occurs after 6 months at room temperature, whereas sodium cloxacillin obtained by precipitation from non-aqueous solvent shows only 6% degradation after 3 years under identical conditions 3.
Critical Storage Pitfalls to Avoid
Never store cloxacillin solutions at room temperature beyond 24 hours, as beta-lactam antibiotics like cloxacillin are particularly unstable and should not be stored in prepared agar plates or solutions without demonstrated stability data 1. The degradation accelerates significantly with:
- Increased temperature exposure: Each temperature increment substantially reduces shelf life 1, 2
- Repackaging from original containers: Unit-dose repackaging accelerates degradation compared to manufacturer containers 2
- Dilution: More dilute concentrations lose potency more rapidly than concentrated solutions 1
Practical Recommendations for Clinical Use
For hospital-based preparation: Mix cloxacillin solutions fresh when possible, or prepare in batches that will be used within 3 days when stored at 4°C 1. Label all reconstituted solutions with the date and time of preparation and the expiration date 1.
For outpatient parenteral antimicrobial therapy (OPAT): Cloxacillin's limited stability at room temperature (1 day) makes it less suitable for extended home infusions compared to agents with longer stability profiles 1. If used for OPAT, ensure patients have adequate refrigeration and use solutions within 3 days of preparation 1.
For oral suspensions: Store in the refrigerator and discard after 7 days for refrigerated storage or 21 days if frozen 2. Do not use solutions that show visible particulate matter, discoloration, or turbidity 1.
Quality Assurance Measures
Solutions should be prepared using sterile technique by trained personnel 1. Before administration, always visually inspect for particulate matter or discoloration 1. Any solution stored beyond recommended time periods or temperature ranges should be discarded 1.