Preparation of Admixtures

Admixtures of ketamine and morphine were prepared by combining enough ketamine hydrochloride (50 mg/mL; Sandoz Canada Inc, Boucherville, Quebec, lot 129290, expiry November 2007) and morphine sulphate (50 mg/mL; Sandoz Canada, lot 130307, expiry July 2007) with sufficient 0.9% sodium chloride (normal saline [NS]) to make solutions with final ketamine concentration of 2 mg/mL and final morphine concentrations of 2, 5, or 10 mg/mL.

Sample Collection

Portions of each solution (30 mL) were packaged in six 60-mL polypropylene syringes (Becton Dickinson and Company, Franklin Lakes, New Jersey), which were sealed with syringe caps. Samples (5 mL) were collected from each syringe into glass vials and frozen at —70°C for analysis at a later date. viagra jelly

Three syringes of each mixture were stored at 23°C with exposure to light, and three were stored at 5°C with protection from light. On days 7, 14, 28, 56, and 91, additional samples were similarly collected and frozen.

Physical Compatibility

To check for precipitation, samples from each syringe were inspected with the aid of a 4x illuminated magnifying light against a black background. Colour change was visually moni­tored with a white background. A calibrated pH meter with a silver—silver chloride electrode (Accumet 25, Fisher Scientific, Nepean, Ontario) was used to measure the pH of samples on each study day.
HPLC Assay

Chromatographic System

The assay method was a modified version of a previously published procedure. The main modification was a decrease in concentration of the organic component of the mobile phase from 43% to 25% acetonitrile; in addition, the final pH was adjusted to 5.0 instead of 3.0 with sodium hydroxide 5N (Fisher Scientific, lot SC6135444, expiry May 2008). The final mobile phase was filtered through a 0.45-^m nylon filter and degassed. canadian drugstore online

The mobile phase was pumped through a 5-^m C18 4.6 x 250 mm column (Luna ODS 18[2] column, Phenomenex Inc, Torrance, California, lot 410754) at a rate of 1.0 mL/min using an isocratic delivery pump (model LC-10AS, Shimadzu Corporation, Kyoto, Japan). A photodiode array detector (model SPD-M6A, Shimadzu Corporation) was set at 270 nm to monitor the peaks of ketamine, morphine, and the internal standard. An autoinjector (model SIL-10AXL, Shimadzu Corporation) was used to inject the 50-^L samples. Phenol (Fischer Scientific, 0.3 mg/mL, lot 026530) was used as the internal standard.

Assay ValidationForcibly degraded samples of ketamine and morphine were used to prove the specificity of the HPLC method. Three sets of solutions containing either ketamine or morphine (5 mg/mL) were prepared. In the first set of solutions, the pH was adjusted to about 1.8 with concentrated hydrochloric acid (BDH, Toronto, Ontario, lot 120834/78180). Sodium hydroxide 5N was used to adjust the pH of the second set of solutions to about 12.2. For the third set of solutions, 1 mL 30% hydrogen peroxide (Fisher Scientific, lot 043211) was added to 9 mL of each stock solution. The acidic and alkaline solutions were incubated in a water bath (Isotemp model 202S, Fisher Scientific) set at 60°C. The solutions containing hydrogen peroxide were kept at room temperature. All solutions were analyzed at time 0 and then at 1, 29, 53, 83, 151, 173, 198, 221, and 245 h for interfering peaks.
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The purity of all peaks was determined through the use of multiwavelength (270 and 254 nm) and ultraviolet (UV) spectral analysis (200-350 nm). The UV spectra of the ketamine and morphine degradation peaks were compared with the reference material for each compound, and correlation coefficients were calculated for all comparisons.

Five replicate injections at 3 separate time points were used to assess intraday variations and to calculate the coefficient of variance (CV) for each drug. Interday variation of the assay method was based on changes to the slopes, linear coefficients, and average areas from 5 separate days. The CV for each parameter was determined. The accuracy of the method was determined from 5 recovery samples for each drug. The lowest concentration that generated a detectable peak while still retaining a linear relationship was defined as the sensitivity of that assay. Least-squares regression analysis was used to assess the linearity of all standard curves.

Stability Study

On the day of analysis, the vials of test solution were allowed to thaw for a minimum of 2 h; the samples were then further diluted either 1:10 (for samples containing 2 mg/mL of both ketamine and morphine) or 1:25 (for samples containing 2 mg/mL ketamine with 5 mg/mL morphine and those containing 2 mg/mL ketamine with 10 mg/mL morphine) after addition of the internal standard. Samples from each syringe were analyzed in duplicate (total n = 6). The admixtures were considered chemically stable if they retained 90% of the original concentrations (i.e., at time zero). Cialis Jelly