Supersaturated state of diazepam injection following dilution with infusion fluid

Abstract

Background: Significant precipitation produced by the dilution of diazepam (DZP) injection with an infusion fluid is a great concern for the clinical practice. In this study, the precipitation behavior under different conditions was investigated.

Method: For the sample preparation, DZP injections (Horizon injection and Cercine injection) were diluted with various infusion fluids (Saline, 5% glucose infusion fluid and Soldem 3A) at designated dilution ratios ranging from 1× to 40× (5 mg/mL to 0.125 mg/mL). In addition, to measure the solubility of DZP in the samples, the saturated solutions of DZP were prepared. The DZP concentrations in the samples were measured by high-performance liquid chromatography (HPLC). This study also investigated the precipitate using various analytical methods: infrared microscopy, (1)H-NMR, differential scanning calorimetry, and powder X-ray deflection.

Results: First, the compatibility of injection with infusion fluids was investigated. Significant precipitation occurred at dilution ratios ranging from 2× to 20×. No significant effects of formulations and infusion fluids on the compatibility were observed. The solubility of DZP was then further investigated. The concentration of DZP dissolved in the admixtures was higher than the solubility. This indicated that DZP existed in a supersaturated state in the infusion fluid admixtures. In the next phase of this study, the precipitate was investigated using various analytical methods. Results showed that the precipitate in infusion fluid admixtures was mostly composed of DZP, but also contained small amounts of the ingredients of DZP injection, such as benzoic acid and benzyl alcohol.

Conclusions: This study clarified details of the precipitation occurring after dilution of DZP injection with infusion fluids. It is worth noting that DZP in an infusion admixture existed in a supersaturated state. These findings offer important insight into the clinical practice of DZP injection.

Keywords: 1H-NMR; Diazepam injection; IR microscopy; Infusion fluids; Precipitation; Supersaturated state.

Figure 1

Precipitation behaviors as a function of (a) marketed products of DZP and (b) infusion fluids. (a) Horizon injection or Cercine injection was diluted with purified water. (b) Horizon injection was diluted with saline, purified water, 5% glucose injection, and Soldem 3A. Horizon injection was completely dissolved in acetonitrile/water (50:50 v/v), and it was used as a control. Each value represents the mean ± S.D., N = 3.

Figure 2

Solubility curve of DZP in the injection diluted with purified water. DZP injection was diluted with purified water, in various dilution ratios, at 25°C, after which excessive amounts of DZP powder were added to the DZP injections diluted with water to prepare the saturated solutions. Each value represents the mean ± S.D., N = 3.

Figure 3

Microscopic images (a) and FTIR spectra (b) of the precipitate and analytical-grade DZP. The region of interest for the measurement of the IR spectra is indicated by a square. The aperture sizes used for the precipitate and analytical-grade DZP were 100 μm × 100 μm and 30 μm × 30 μm, respectively. The y-axis of each spectrum has arbitrary units.

Figure 4

Powder X-ray diffraction patterns of the precipitate and analytical-grade DZP.

Figure 5

¹ H-NMR spectra of the precipitate, analytical-grade DZP, benzoic acid and benzyl alcohol dissolved in CD ₃ OD.

Figure 6

DSC thermograms of the precipitate and analytical-grade DZP. The y-axis of each spectrum has arbitrary units.