Stability of Hydromorphone-Ketamine Solutions: METHODS part 2

Preparation of Samples

The hydromorphone—ketamine study samples were thawed, mixed by vortex mixer for 10 s, and prepared as follows. For samples with nominal concentrations of hydro­morphone 0.2 mg/mL and ketamine 0.2 mg/mL, a 0.5-mL aliquot was diluted with 0.1 mL naloxone (internal standard) and 0.4 mL NS. For samples with nominal concentrations of hydromorphone 0.2 mg/mL and ketamine 0.6 mg/mL or 1.0 mg/mL, a 0.25-mL aliquot was diluted with 0.1 mL naloxone and 0.650 mL NS. The final theoretical concentra­tions of hydromorphone and ketamine, respectively, after sam­ple preparation were as follows (mg/mL): 0.1 and 0.1, 0.05 and 0.15, 0.05 and 0.25. In addition, a quality control sample (hydromorphone 0.15 mg/mL and ketamine 0.15 mg/mL) was added to each HPLC run. Each sample was passed through a 0.45-^m microfilter before a 25-^L sample was withdrawn and injected onto the column.

HPLC Instrumentation

The HPLC instrumentation (model 2690, Waters Alliance System, Waters Ltd, Mississauga, Ontario) consisted of a delivery pump, an automatic injector system equipped with a 200-^L injector, an Atlantis dC18 4.6 x 150 mm column (Waters Ltd; lot 01293709613840), an Atlantis dC18 3.9 x 20 mm guard column (Waters Ltd; lot 129371141), and an ultra­violet detector set at 203 nm. The mobile phase was developed in the authors’ laboratory and consisted of a gradient mixture of 11%-52.5%-90%-11% methanol (Fisher Scientific, Richmond, British Columbia; lot D0372) and 89%—47.5%-10%-89 % of 5 mmol/L potassium phosphate buffer (Sigma-Aldrich Canada Ltd, Oakville, Ontario; lot 125K0169) with 10 mmol/L ethylenediaminetetra-acetic acid (Sigma-Aldrich Canada Ltd; lot 11K0315) at pH 3.15 over a period of 10 min. All solvents were HPLC-grade and were filtered before use. The flow rate was set at 1.2—1.5 mL/min. Viagra Super Active

Degradation of Hydromorphone and Ketamine

A mixture of hydromorphone 0.25 mg/mL and ketamine 1 mg/mL was prepared from 1 mg/mL stock solutions of each drug. The pH was adjusted to 9.0 with sodium hydroxide 2N, and the sample was incubated for 18 h at 90°C. The sample was cooled to room temperature, the pH was readjusted to 4.1 with hydrochloric acid 1N, and the sample was boiled for 10 min. The sample was then adjusted with NS to final concentrations of hydromorphone 0.05 mg/mL and ketamine 0.20 mg/mL, filtered, and injected onto the column. The chromatogram obtained for the degraded preparation was compared with a chromatogram obtained from the standard curve to determine any changes in concentration, retention time, and peak shape.

Sterility of Hydromorphone and Ketamine Mixture

A 5-mL sample of each combined solution of hydromor- phone and ketamine was drawn from each syringe and IV bag on day 0 (immediately after preparation of the solutions) and was incubated in 10 mL of thioglycolate-enriched culture broth to test for the presence of both anaerobic and aerobic bacteria. The mixtures were placed in an ambient air incubator at 35°C for 5 days. Absence of bacterial growth after 5 days under these conditions was considered to indicate sterility.
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Statistical Analysis

Means, standard deviations, and coefficients of variation were calculated for samples analyzed in triplicate or quadruplicate. For each study day, the percentage of the initial hydromorphone and ketamine concentrations remaining was calculated for each sample. The percentage of hydromorphone and ketamine remaining on day 7 was calculated from the concentration on day 7, as determined by linear regression and the concentration observed on day 0, according to the following formula: (concentration on day 7/concentration on day 0) x 100%. The 95% confidence interval (CI) of the amount remaining on the last study day was calculated from the lower limit of the 95% CI of the slope of the curve relating concen­tration to time, determined by linear regression, via computer analysis, according to the following formula: lower limit of the 95% CI of (concentration on day 7/concentration on day 0) x 100%. Stability was defined as maintenance of at least 90% of the initial hydromorphone and ketamine concentrations.

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