Preparation of Admixtures

Test admixture solutions containing lidocaine 9 or 18 mg/mL were prepared aseptically in a laminar airflow hood by diluting 46.36 mL of either lidocaine 1% (AstraZeneca Canada Inc, Mississauga, Ontario; lot 99240052, expiry February 2010) or lidocaine 2% (AstraZeneca Canada Inc; lot 99232851, expiry December 2009) with 4.64 mL of sodium bicarbonate 8.4% (Hospira Healthcare Inc, Montreal, Quebec; lot 54202EV, expiry June 2009) in an empty polyvinylchloride IV bag. Multidose lidocaine vials were used. Polypropylene syringes (3 mL, Becton Dickinson and Company, Franklin Lakes, New Jersey) were then filled with 3-mL samples of the admixtures and stored at 5°C (range 4°C to 7°C) in an unlit refrigerator.

Solutions containing both lidocaine and epinephrine were prepared, packaged, and stored in the same way as described above, using 81.82 mL of either lidocaine 1% – epinephrine 1:100 000 (AstraZeneca Canada Inc; lot NL2073, expiry August 2009) or lidocaine 2% – epinephrine 1:100 000 (AstraZeneca Canada Inc; lot NL2283, expiry February 2010) combined with 8.18 mL of sodium bicarbonate 8.4% (Hospira Healthcare Inc; lot 54202EV, expiry June 2009). discount drugs canda

Sample Collection

Immediately after preparation (day 0), the contents of 3 syringes for each of the 4 admixtures were transferred to individual glass vials and frozen at -70°C in a scientific freezer (model 992, Thermo Fisher Scientific Inc, Marietta, Ohio). On days 7, 14, 21, and 28, additional samples of all solutions were collected, as described previously, inspected, and then frozen in an identical manner. On days 3, 10, 17, and 24, samples of solutions containing both lidocaine and epinephrine were collected, inspected, and frozen. The study samples were analyzed for both lidocaine and epinephrine, as appropriate, once all of the samples had been collected; the final samples collected remained in the freezer for 1 month before analysis.

Physical Compatibility

On each sampling day, the same investigator (R.F.D.) inspected each sample for the appearance of particulate matter against a black background and for colour change against a white background. pH was determined on each sampling day using a calibrated pH meter with a silver-silver chloride electrode (Accumet model 25, Fisher Scientific Ltd, Nepean, Ontario). Buffers at pH 7.00 (Fisher Scientific Ltd; lot SC7134746, expiry May 31, 2009) and 10.00 (Fisher Scientific; lot SC6195146, expiry September 30, 2008) were used to calibrate the pH meter before each use. pharmacy uk

Chemical Stability Study

High-Performance Liquid Chromatography System

The collected samples were analyzed using validated stability- indicating high-performance liquid chromatography (HPLC) methods. The analytical system consisted of an isocratic pump (model LC-10AT, Shimadzu Corporation, Kyoto, Japan), a photodiode array detector (model SPD-M6A, Shimadzu Corporation), and an auto-injector (model SIL-10AXL, Shimadzu Corporation) coupled with sample cooler (model S, Shimadzu Corporation) set at 4°C. A 5-^m, 4.6 x 250 mm C18 column (Luna, Phenomenex Inc., Torrance, California; lot 410754) was used. Class-VP software (version 4.2, Shimadzu Corporation, Columbia, Maryland) was used for data collection and analysis.

The samples were analyzed for epinephrine content using the USP method, and the lidocaine content was determined using a modified USP method.9 The modifications to the lidocaine method, intended to enable separation of the degrada­tion products from the parent compound, were a decrease in the organic phase to 15%, adjustment of the pH to 2.5, and addition of an amine modifier (0.2% triethylamine).The flow was set at 1.5 mL/min, and peaks were monitored at 270 nm. Fifty-microlitre samples were injected onto the column. All other conditions were as listed in the USP monographs. cialis 5 mg

Ciprofloxacin 0.01 mg/mL (Bayer Inc, Toronto, Ontario; lot 2500LXN, expiry January 2008) was used as the internal standard in the lidocaine assay.