Intravenous Suitability Studies of Commonly Used Oxacillin Sodium Solutions in the Accufuser ® Infusion Device

Our study compares two commonly used solutions of oxacillin sodium, 5.0 mg/mL in either 0.9% sodium chloride (NS) or 5% dextrose water (D5W), for their continued suitability for IV usage, and stability of active compound over time, when stored at two different controlled temperatures for six weeks. Both solutions were stored in an intravenous infusion device commercially available as Accufuser® and kept at a continuously maintained temperature of either 4 ± 2 ̊C (CT) or 25 ± 2 ̊C (RT). Suitability for IV administration was assessed by measuring changes in macrographical transparency and pH over time, and drug stability was assessed by measuring changes in oxacillin concentration over time using high-performance liquid chromatography (HPLC). After 6 weeks, concentrations of oxacillin were unchanged in the CT solutions, while both RT solutions showed significant decreases in the concentration of oxacillin after only two weeks. Final concentration compared to starting concentrations after 6 weeks at RT, were 36.57% in NS, while virtually no oxacillin was detectable in D5W. Also pH measurements showed a slight decrement at 2 weeks with RT and at 6 weeks, there was a significant change in pH in both NS and D5W at RT. There was no significant change in color, transparency or appearance after 6 weeks in any of the oxacillin solutions stored in the Accufuser® infusion device. In summary, two commonly used IV solutions for oxacillin administration (5 mg/mL in NS or D5W) stored in the Accufuser® showed significant changes over time when maintained at RT, that would make the solutions inappropriate for therapeutic use. Both solutions when maintained in CT were not significantly altered and continued to be appropriate in pH and drug concentration for IV therapy. This suggests that ready-to-use solutions of oxacillin sodium in the Accufuser® infusion device can be kept at CT for up to 6 weeks safely but should not be stored at RT due to loss of potency and changes in pH.


Introduction
The disposable silicon balloon infusion device, Accufu-ser® is a well-established simplified silicon-based elastomeric device for administration of antibiotics and other drugs that is suitable for patients or caregiver operation, as well as for use by healthcare providers.An increasing number of patients are being treated as outpatients and in these patients, drugs are often infused using portable pumps or infusion devices.Therefore, it is necessary that studies determine the physical and chemical stability of its admixtures in this infusion system before they appear in the clinical settings [1][2][3][4][5][6].This paper will be to provide such information with commonly used antibiotics solutions in Accufuser® elastomeric infusion device under recommended storage conditions.The purpose of this study was to evaluate the intravenous suitability and physical and chemical stability of oxacillin sodium (Figure 1, 5.0 mg/mL, normal saline, NS and 5% dextrose, D5W) solutions packaged in sterile Accufuser® device stored and evaluated at appropriate intervals up to 6 weeks at different storage conditions with room (RT, 25 ± 2˚C) and cold temperature (CT, 4 ± 2˚C).The study was performed with oxacillin sodium solution that made with NS and D5W because these are the most available infusion solution for oxacillin administration in clinical situations [2,[6][7][8][9][10].

Materials
Oxacillin sodium was purchased from Fluka Co., Milwaukee, MI, USA.Normal saline (NS, 0.9% sodium chloride in water) and 5% dextrose (D5W, injectable 5% dextrose water) were purchased from JW Pharmaceutical Co., Seoul, Korea.Disposable Silicone Balloon Infuser (Accufuser®) was obtained from Woo-Young Medical Co., LTD, Seoul, Korea.Acetonitrile and potassium phosphate were purchased from Sigma-Aldrich Co., St. Louis, MO, USA.Milli-Q water from Millipore's Milli-Q system (MA, USA) was used throughout the analysis.All chemicals for HPLC analysis were all HPLC-grade and were prepared immediately before use.

Preparation and Sampling of Solutions
To prepare the test samples, the appropriate amounts of oxacillin sodium were added to a portion of the infusion solution and then were brought to a final volume of 100 mL with NS and D5W.The test solutions were packaged in sterile Accufuser® device for testing.All manipulations were performed in a biological safety cabinet.The nominal oxacillin sodium concentration for testing was 5.0 mg/mL and triplicate test solutions under each storage test conditions were prepared.The test solutions were stored at RT and CT conditions.Aliquots were taken from each device initially and at the intervals of 48 h, 1, 2, 4, and 6 weeks at RT and CT conditions and determined its concentration by the HPLC method (Table 1).

Physical Stability
The physical stability of the oxacillin infusion solutions   was assessed by visual examination and HPLC analysis.
diffuse fluorescent room light with naked eye and a highintensity mono-directional light.The pH of solutions was measured with a stainless electrode pH meter (Thermo Scientific Co., MA, USA).The drug concentrations were determined using a stability-indicating HPLC assay method based on several literatures [2,[10][11][12][13].

Validation of the HPLC Method
The method was validated for linearity, precision ivity [10].
nt changes in physical appearance or cla tions were observed during the study concentration range of 0.5 -7.5 mg/mL (r = day and intra-day), accuracy, and select The 0.9998, Figure 3(a)).Table 3 lists the relative standard deviation (R.S.D.) data obtained on analysis of the samples (n = 3) on the same day and on consecutive days (n standard plot was constructed for oxacillin sodium in the range of 0.5 -7.5 mg/mL.The experiment was repeated 3 times on the same day and additionally on 2 consecutive weeks to determine intra-and inter-day precisions.Assays of control solutions at oxacillin sodium solutions (5.0 mg/mL) were undertaken to calculate the intra-day and inter-day variations using external standard method.Linearity was evaluated by serial dilutions of oxacillin sodium solutions with NS and D5W for loading.Linear regression analysis of peak area and drug concentration yielded a correlation >0.99 (range 0.5 -7.5 mg/mL).The stability of oxacillin infusion solution is determined in disposable silicone balloon infuser (Accufuser®) during 6 weeks of storage under RT and CT.Solutions of oxacillin sodium with concentrations 5.0 mg/mL are prepared with NS and D5W.Two kinds of oxacillin sodium solutions are filled with 10 mL of each in three Accufu-ser® and stored at room and cold temperature cabinets.Then, each Accufuser® containers are filled with the same volume of different solutions (NS and D5W) and different temperatures (RT and CT) [1,3].All the samples are stored at RT and CT.Periodically; the samples are evaluated for appearance, visible particles, pH and chromatographic parameters.We analyzed the amount of oxacillin sodium in each two solutions at 0, 48 h, 1, 2, 4, and 6 weeks after making solutions by HPLC-UV system [1,7,10].On each analysis day, 1.0 mL of samples for chromatographic analysis with a nominal concentration of 5.0 mg was drawn from Accufuser® device and 2.0 µL were directly injected into HPLC system for analysis.
The three aliquots of each solution were processed.Statistical analysis was performed using one-way ANOVA with the level of significance set at 0.05 (PCS, version 4.0, Springer-Verlag, New York, USA).

1)
No significa ity of the solu r-.The n colors of the samples were transparent with no changes of color.The particles are not detected in any samples.
2) Slight decrement of NS and D5W solutions in pH from 5.56 to 5.32 and from 5.55 to 5.45 was observed i cold storage, respectively and shown similar pattern in NS solutions in RT conditions.But it was shown different pattern with significant changes in D5W solution and reached to 3.6 at 6 weeks in the RT conditions (Table 2, Figure 2).
3) The linearity could be established for oxacillin sodium in the  .values were <1.37% and <2.93% for intra-day and inter-day results, respectively, lor or clarity was tions during the = 5).As evident, the R.S.D meaning that the method was sufficiently precise.
4) The retention time for oxacillin sodium in the chromatogram was about 12.8 min.The typical HPLC chromatogram of oxacillin sodium (5.0 mg/mL) was shown in the Figure 3(b).The initial concentration and the percentages of oxacillin sodium on each appointed analytic point during the study period for each solutions and a storage condition is listed in the Table 3 and Figure 4.The HPLC analysis showed that the amount of oxacillin sodium was remained about initial values at CT up to 6 weeks in NS and D5W solutions.But it was significantly decreased to 36.57% in NS solution and disappeared in D5W solution at 6 weeks at RT.

Discussion and Conclusions
No visible precipitation or change in co observed in any kinds of oxacillin solu study.We observed that the intravenous suitability and stability of oxacillin is affected by temperature of storage (more stable in CT than RT) and solution (stable in NS than D5W).When oxacillin solution is made according to the sponser's opinion to achieve concentrations of 50 mg/mL in NS and D stored in an Accufuser® and retained 36.57% and 0.00% at RT up to 6 weeks, respectively.Otherwise, when oxacillin solution is made according to the sponser's opinion to achieve concentrations of 50 mg/mL in NS and D5W and analyzed 5.0 mL solutions after 10 times dilution of each solution that stored in an Accufuser® and retained 104.95% and 102.14% at RT up to 6 weeks, respectively.Therefore, 5.0 mg/mL of oxacillin sodium solutions of NS and D5W were stored in CT and stable and retained about their initial concentration into Ac-cufuser® up to 6 weeks, but shown unstable and its con- T: room perature, 2) CT: cold temperature, 3) NS: norm saline, 4) D5W: ctable 5 dextrose water, * Mean ±SD (%), * p < 0.05 vs. 0 h., S. Y. Kim and J. S. Kang, "Stability of Commonly Used centrations significantly decreased after 1 week in RT conditions.In conclusion, two commonly used IV solu-D5W) stored ready to use in the Accufuser® showed significant changes over time when maintained at RT, that would make the solutions inappropriate for therapeutic use.Both solutions when maintained in CT were not significantly altered and continued to be appropriate in pH and drug concentration for IV therapy.This suggests that ready-to-use solutions of oxacillin sodium in the Accufuser® infusion device can be kept at CT for up to 6 weeks safely but should not be stored at RT due to loss of potency and changes in pH.
test of oxacillin Na solutions in Accufuser® device.

Figure 2 .
Figure 2. The changing plots of pH of oxacillin 5.0 mg/mL solutions over time of storage.

Figure 4 .
Figure 4.The changes of amount (mean ±SD, %) of oxacillin in various solutions (NS, D5W) according to storage temperature (RT and CT) and periods.