Cloxacillin sodium is available as a dry powder in vials containing 500 mg, 1 g, and 2 g of cloxacillin as the sodium salt.3248 The drug also is available in a pharmacy bulk package containing 10 g of cloxacillin as the sodium salt.3248
For intramuscular use, 1.7 mL of sterile water for injection should be added to the 500-mg vial, and the vial should be shaken well to yield a solution with a nominal concentration of 250 mg/mL.3248
For intravenous use, 4.8 or 9.6 mL of sterile water for injection should be added to a 500-mg or 1-g vial, respectively, and the vial should be shaken well to yield a solution with a nominal concentration of 100 mg/mL.3248
For intravenous infusion, 3.4 or 6.8 mL of sterile water for injection should be added to the 1- or 2-g vial, respectively, and the vial should be shaken well to yield a solution with a nominal concentration of 250 mg/mL, which is then added to an appropriate infusion solution for administration.3248 The 10-g pharmacy bulk package should be reconstituted with 34 mL of sterile water for injection and shaken well to yield a solution with a nominal concentration of 250 mg/mL, which is then added to an appropriate infusion solution for administration.3248
Sodium Content
Each gram of cloxacillin sodium contains approximately 50 mg of sodium.3248
Cloxacillin sodium may be administered by intramuscular injection, direct intravenous injection slowly over 2 to 4 minutes, or by intravenous infusion (following dilution in an appropriate infusion solution) over 30 to 40 minutes.3248
Intact vials containing the drug in dry form should be stored at controlled room temperature.3248 After reconstitution with sterile water for injection, cloxacillin solutions are stable for up to 24 hours at controlled room temperature not exceeding 25°C or 48 hours under refrigeration at 2 to 8°C.3248
Cloxacillin sodium (Beecham) 250 mg reconstituted with 1.5 mL and 500 mg reconstituted with 2 mL of sterile water for injection exhibited a 5% loss in 7 days at 5°C and a 15% loss in 4 days at 23°C.99
Cloxacillin sodium (Ayerst) 20 g/L in sodium chloride 0.9% or dextrose 5% was stored in polyvinyl chloride (PVC) minibags (Travenol) or glass bottles (Travenol) for 24 hours at 5 and 22°C. No significant decrease in antibiotic stability was observed at 24 hours in sodium chloride 0.9% in either container. With dextrose 5%, a decrease in cloxacillin was observed at 24 hours. The results indicated that cloxacillin sodium was stable for 24 hours in sodium chloride 0.9% and for 8 hours in dextrose 5%.298
pH Effects
Cloxacillin sodium is most stable at a pH of 5.5 to 7, with a minimum decomposition rate at pH 6.3.1476; 1477
Freezing Solutions
Cloxacillin sodium (Beecham) at concentrations of 1 to 10%, buffered to pH 6.05, lost no more than 1% potency in 1 month when frozen at -20°C.99
Cloxacillin sodium (Beecham) 1 g in 50 mL of dextrose 5% or sodium chloride 0.9% in PVC containers (Travenol) was frozen at -20°C for 30 days, followed by natural thawing and storage at 5°C for 21 hours. The cloxacillin concentration was retained for the duration of the study.299
Cloxacillin sodium 2 g in 100 mL in dextrose 5% or sodium chloride 0.9% in PVC containers was frozen at -27°C for up to 9 months and then thawed by microwave. The results indicated that at least 90% of the concentration was retained. A distinct yellow discoloration was observed in solutions in dextrose 5% stored for 6 months. Consequently, the authors recommended that such frozen solutions not be stored for more than 3 months.1176
Cloxacillin sodium (Beecham) 500 mg in 50-mL PVC bags (Travenol) stored at -20°C and thawed under natural conditions was stable for at least 100 days. In addition, the drug was stable under refrigeration for 4 days followed by 24 hours at room temperature after thawing.1478
Sorption
Cloxacillin sodium was shown not to exhibit sorption to PVC bags and tubing, polyethylene tubing, Silastic tubing, and polypropylene syringes.536; 606
Filtration
Cloxacillin sodium (Beecham) 1.97 mg/mL in sodium chloride 0.9% or dextrose 5% was filtered through a 0.22-µm cellulose acetate membrane filter (Ivex-HP, Millipore) over 6 hours. No significant loss due to binding was noted.1034
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