Compatibility and Physical Properties of Dexamethasone-Ondansetron Intravenous Admixture

Abstract

Purpose: This work aimed at evaluating the impact of different concentrations and final volumes on the compatibility and physical properties of dexamethasone-ondansetron intravenous (IV) admixture. Methods: The IV admixture of dexamethasone-ondansetron was prepared at different concentrations using normal saline solution as solvent. The final volume of the IV admixture was prepared at 50 and 100 ml. Turbidity was measured as an indicator of physical compatibility of the IV admixture of dexamethasone-ondansetron using UV-visible spectrophotometer and the pH of the IV admixture was measured on day 0, 7,14, and, 21 as an index of chemical stability. Also, the particle size and potential molecular interactions of the admixtures were determined using particle size analyzer and Fourier Transform infrared spectrometry analysis, respectively. Additionally, the effect of preservatives on the IV admixture was also evaluated. Results: Precipitation was observed for mixtures with amounts of dexamethasone and ondansetron exceeding 8 and 16 mg, respectively, in a final volume of 50 ml. For all mixtures with final volume of 100 ml, clear solutions void of any precipitates were observed. The pH of the solution had no effect on the precipitation of the dexamethasone-ondansetron during storage up to 21 days. Analyses of the precipitate formed revealed the presence of molecular interactions between dexamethasone and ondansetron. The benzyl alcohol used as a preservative affected the compatibility of the IV admixture compatibility. Conclusion: Thus, for the preparation of clear, physically compatible normal saline solutions of dexamethasone-ondansetron IV admixture, the maximum amounts of the respective drugs should not exceed 8 and 16 mg in total volume of 50 ml or 20 and 16 mg in a final volume of 100 ml.

Introduction

The incidence of nausea and vomiting from chemotherapy has a significant impact on the quality of life of cancer patients. Such symptoms also result in other problems, such as loss of water and minerals as well as loss of appetite, which lead to insufficient nutrient intake. As a result, patients may experience a prolonged chemotherapy treatment cycle, failure in treatment adherence or even stop the chemotherapy regimen entirely. The antiemetic guidelines recommend the use of a 2-drug combination, namely serotonin 5-HT3 receptor antagonists and dexamethasone. These are administered prior to administering chemotherapy to prevent acute nausea and vomiting from moderately emetogenic chemotherapy such as carboplatin, doxorubicin, irinotecan. ¹ The most commonly used serotonin 5-HT₃ receptor antagonist in combination with dexamethasone is ondansetron (Figure 1). The treatment guideline for combination of the antiemetics recommends 8 to 16 mg intravenous (IV) dose of ondansetron and 12 mg IV dose of dexamethasone at once. ² However, for highly emetogenic chemotherapy, dexamethasone of up to 20 mg IV dose had been previously used.^3,4

Figure 1.

The chemical structure of ondansetron (A) and dexamethasone (B).

Data from previous compatibility study of ondansetron and dexamethasone IV admixture with normal saline and 5% dextrose as diluents, indicated that the IV admixture may not be theoretically compatible. The incompatibilities that occurred may be due to the complex of the positive charge of ondansetron and the negative charge of dexamethasone. In addition, the high pH of the IV admixture may be responsible for the precipitation of ondansetron in the free base form. ⁵ Subsequent studies on the compatibility of ondansetron (8 and 32 mg) combined with dexamethasone (20 mg) and diluted with normal saline solution (NSS) or 5% dextrose in a total volume of 50 ml, reported that the admixture was physically compatible and chemically stable for only 24 hours. ⁶ In another report it was observed that the IV admixtures of ondansetron (5 or 10 mg) combined with dexamethasone (20 mg) in 20 ml of NSS as well as ondansetron (30 mg) with dexamethasone (20 mg) in 30 ml of NSS were both incompatible. ⁷ In addition to the concentration factors mentioned above, it was found that the preservative used in dexamethasone commercial products also had an effect on precipitation of the admixture, albeit the concentration of preservative was not mentioned. ⁸

Against this backdrop, it is apparent that the concentrations of the different components might play a role in the compatibility of the IV admixture; however, this is yet to be investigated in detail. The purpose of this study was therefore to evaluate how different drug component concentrations and final volumes affect the physical compatibility and stability of dexamethasone-ondansetron intravenous admixture to be used as antiemetic medicines for cancer patients. Moreover, the effect of preservatives, compounded hydroxybenzoate solution (parabens) and benzyl alcohol, on precipitation of dexamethasone-ondansetron were also examined.

Materials

Normal saline solution and sterile water for injection in a polypropylene bottle were purchased from General Hospital Products (Bangkok, Thailand). Ondansetron Hydrochloride (OND) powder and dexamethasone sodium phosphate (DEX) were obtained from Siam Pharmaceutical (Bangkok, Thailand) and Nida Pharma Incorporation (Bangkok, Thailand), respectively. Methyl hydroxybenzoate and propyl hydroxybenzoate were obtained from BioDent International (Bangkok, Thailand). Benzyl alcohol was purchased from Merck Millipore (Darmstadt, Germany). All other chemical reagents were of American Chemical Society (ACS) grade.

Methods

Samples Preparation

Stock solution of 4 mg/ml OND was prepared by dissolving 0.1 g of OND with 25 ml NSS injection. Stock solution of DEX (10 mg/ml) was prepared by dissolving 0.25 g of dexamethasone sodium phosphate powder with 25 ml NSS injection. Various binary mixtures of OND and DEX stock solutions were prepared and adjusted using NSS injection to final volume of 50 or 100 ml. The final weight ratios of OND and DEX for all samples are shown in Table 1. OND at 8 mg in 50 ml solution, DEX at 40 mg in 50 ml solution, and NSS injection were used as controls. All samples were kept in 4°C and protected from light.

Table 1.

The Sample Preparation of OND and DEX Mixtures.

Sample no.	Drug amount		Final volume (ml)	Final concentration
	DEX (mg)	OND (mg)		DEX (mg/ml)	OND (mg/ml)
1	8	8	50	0.16	0.16
2	16	8	50	0.32	0.16
3	20	8	50	0.40	0.16
4	8	16	50	0.16	0.32
5	16	16	50	0.32	0.32
6	20	16	50	0.40	0.32
7	8	8	100	0.08	0.08
8	16	8	100	0.16	0.08
9	20	8	100	0.20	0.08
10	8	16	100	0.08	0.16
11	16	16	100	0.16	0.16
12	20	16	100	0.20	0.16

Turbidity Measurement

Sample turbidity due to drug-drug precipitation was measured using UV-Visible Spectrophotometer, Spectroquant Prove 100 (Merck Co., Darmstadt, Germany) with a 100-mm cuvette. The turbidity assay was carried out at 25°C and recorded in nephelometric turbidity units (NTU). Samples that presented clear solutions were measured at day 0, 7, 14, and 21. All samples were measured in triplicate.

Particle Size Analysis

Drug-drug aggregation of the samples were evaluated using particle size analysis carried out with Zetasizer Nano ZS (Malvern Instruments, Malvern, UK). NSS was used as medium. Measurements were taken at a temperature of 25 ± 0.1°C. For each sample, 10 measurements each of 10 seconds were recorded and averaged for a single run. Plots of particle size distribution were obtained covering the range of 0.5 to 5000 nm.

PH Study

The pH of sample solutions were measure using SevenCompact pH/Ion meter S220 (Mettler Toledo, US). Samples pH were measured at day 0, 7, 14, and 21. The pH effect on the precipitation was studied by altering the pH of the DEX-OND mixture solution to acidic (pH = 1) or basic (pH = 14) using either 0.1M hydrochloric or 0.1M potassium hydroxide, respectively. All samples were performed in triplicate.

Fourier Transform Infrared (FTIR) Spectral Analysis

The molecular interaction of DEX and OND was studied using Fourier transform infrared spectroscopy technique. The mixture of DEX and OND was prepared by dissolved 80 mg of DEX and 35 mg of OND using 25 ml of NSS. The DEX-OND solution was subsequently filtered using membrane filter with 0.22 µm pore size. Then, the precipitate was collected and dried in a desiccator. The sample was scanned using Spectrum One FT-IR spectrometer (Perkin-Elmer, Massachusetts, US) at wavenumber 4000 to 400 cm⁻¹. The sample was prepared by mixing with KBr and compressed into a disc. The sample was scanned 64 times.

Effect of Preservatives

Compounded hydroxybenzoate solution (parabens) was prepared via a combination of methyl hydroxybenzoate (8 g) and propyl hydroxybenzoate (2 g) in 100 ml of propylene glycol. ⁹ The DEX-OND solutions sample containing the maximum amount of DEX and OND for which no precipitation was observed was selected. Subsequently, compounded hydroxybenzoate solution or benzyl alcohol was added to a final concentration 0.1% to 0.2% or 2% to 4%, respectively.

Results

Sample Turbidity

The turbidity of DEX-OND samples at 0, 7, 14, and 21 days are shown in Table 2. All DEX-OND solutions prepared at a final volume of 100 ml were clear without any turbidity up to 21 days. The DEX-OND solutions prepared at a final volume of 50 ml exhibited a clear solution for DEX (8 mg) with OND (8 or 16 mg) for up to 21 days. A slightly opaque solution was observed for DEX at 16 and 20 mg. The solution was opaque when the amount of DEX increased; thus, the precipitation may depend on the amount of DEX.

Table 2.

The Turbidity of DEX-OND Samples at 0, 7, 14, and 21 days.

Sample No.	DEX (mg)	OND (mg)	Final volume (ml)	Turbidity (NTU)
				Day 0	Day 7	Day 14	Day 21
1	8	8	50	<1	<1	<1	<1
2	16	8	50	7 ± 0
3	20	8	50	5 ± 0
4	8	16	50	1 ± 0	1 ± 0	<1	1 ± 0
5	16	16	50	3 ± 0
6	20	16	50	13 ± 0
7	8	8	100	<1	<1	<1	<1
8	16	8	100	<1	1 ± 0	1 ± 0	<1
9	20	8	100	1 ± 0	1 ± 0	<1	<1
10	8	16	100	<1	1 ± 0	<1	<1
11	16	16	100	<1	<1	<1	<1
12	20	16	100	<1	<1	<1	<1
13	40	0	50	<1	<1	<1	<1
14	0	8	50	<1	<1	<1	<1
15	0	0	50	<1	<1	<1	<1

Particle Size Analysis

The common clinically used amounts of DEX (20 mg) and OND (8 mg) in 100 ml NSS solution was selected for particle size analysis. DEX-OND sample with high turbidity and DEX concentration, that is, DEX (20 mg) and OND (16 mg) in 50 ml NSS solution, was also selected for particle size analysis. Individual solutions of DEX, OND, and NSS were used as controls. The particle size analysis of all samples were shown in Table 3.

Table 3.

The Particle Size Analysis of DEX-OND Samples.

Sample no.	DEX (mg)	OND (mg)	Final volume (ml)	Size (nm)	Polydispersity
1	20	8	100	736.9	1.011
2	20	16	50	5555.4	0.348
3	40	0	50	3.7	0.598
4	0	8	50	8.8	0.647
5	0	0	50	0.0	0.000

The particle size of individual DEX, OND, or NSS sample was less than 10 nm, whereas the particle size of DEX-OND samples was found to be higher than 700 nm. DEX-OND samples with lower concentrations had smaller particle size than those with higher concentrations. The opaque solution of 20 mg of DEX and 16 mg of OND in 50 ml NSS solution had the largest particle size of 5555.4 nm, whereas the clear solution of 20 mg of DEX and 8 mg of OND in 100 ml NSS solution had a particle size of 736.9 nm. Although, a clear solution was observed for DEX-OND at 20 and 8 mg, the particle size was still larger than those of the single compounds. The large particle size of parenteral formulations was also available in market as a lipid complex parenteral formulation. ¹⁰ Moreover, the compatibility of the IV admixtures of DEX and other serotonin 5-HT3 receptor antagonists was comprehensively investigated. ¹¹

PH Study

The pH of DEX-OND samples at 0, 7, 14, and 21 days were presented in Table 4. The pH range of all DEX-OND samples were in the range of 6.25 to 6.78 for up to 21 days. Generally, OND is a basic drug that can precipitate due to low solubility in basic condition. Thus, the precipitation of DEX-OND samples occurred due to the incompatibility of DEX and OND.

Table 4.

The pH of DEX-OND samples at 0, 7, 14, and 21 days.

Sample no.	DEX (mg)	OND (mg)	Final volume (ml)	pH
				Day 0	Day 7	Day 14	Day 21
1	8	8	50	6.40	6.83	6.74	6.59
2	16	8	50	6.43	6.73	6.71	6.67
3	20	8	50	6.53	6.72	6.69	6.72
4	8	16	50	6.25	6.50	6.54	6.47
5	16	16	50	6.37	6.56	6.48	6.56
6	20	16	50	6.47	6.70	6.62	6.65
7	8	8	100	6.39	6.45	6.55	6.45
8	16	8	100	6.70	6.78	6.40	6.48
9	20	8	100	6.62	6.63	6.59	6.64
10	8	16	100	6.34	6.41	6.47	6.43
11	16	16	100	6.54	6.70	6.64	6.55
12	20	16	100	6.56	6.67	6.61	6.60

Fourier Transform Infrared (FTIR) Spectral Analysis

The incompatibility of DEX and OND was evaluated by analyzing their molecular interactions using FTIR. Physical mixture (PM) prepared by mixing the DEX and OND powder at 1:1 ratio was used as a control. All FTIR spectra of DEX, OND, DEX-OND, and DEX-OND PM were shown in Figure 2. The FTIR spectrum of DEX revealed a broad peak at 3426.83 cm⁻¹ corresponding to O―H stretching. DEX possesses 2 carbonyl groups (C=O), and thus the 2 C=O stretching peaks observed at 1714.72 and 1667.6 cm⁻¹. OND presented N―H stretching peaks at 3485.6 and 3409.4 cm⁻¹, a C―N stretching peak at 1280.6 cm⁻¹, and the C=O stretching peak characteristic of 6-membered ring was observed at 1637.52 cm⁻¹. The FTIR spectrum of the physical mixture (PM) of DEX-OND exhibited broad peak at 3422.6 cm⁻¹ corresponding to O-H group of DEX, and 2 peaks at 1714.6 and 1667.6 cm⁻¹ attributable to the 2 carbonyl groups of DEX. Moreover, the peak at 1637.3 and 1281.4 cm⁻¹ of DEX-OND PM were also observed for the C=O and C-N stretching peak of OND, respectively. In the FTIR spectrum of DEX-OND, the peak corresponding to O-H stretching of DEX was shifted to a lower wavenumber (3406 cm⁻¹) and the C=O stretching peak of OND was also shifted to lower wavenumber (1624.3 cm⁻¹). Furthermore, the N-H stretching peaks corresponding to OND disappeared and one of carbonyl peaks of DEX was shifted to a lower wavenumber (1662.6 cm⁻¹). The FTIR peak shift could be due to the hydrogen bonding interaction between O-H of DEX and C=O of OND or N-H of OND and C=O of DEX, that could be observed in the crystal structures of OND and DEX.^12-14

Figure 2.

The FTIR spectra of dexamethasone (DEX), ondansetron (OND), dexamethasone-ondansetron (DEX-OND) precipitate and physical mixture of dexamethasone-ondansetron (DEX-OND PM).

Effect of Preservatives

Parabens and benzyl alcohol are commonly used as preservatives in parenteral preparations with the recommendation concentrations up to 0.1% and 2%, respectively.^15,16 The sample with 8 mg of DEX and 16 mg of OND in final volume of 50 ml of NSS (Sample No.4) and the sample with 20 mg of DEX and 16 mg of OND in final volume of 100 ml of NSS (Sample No.12) were selected. Into these solutions were added either parabens or benzyl alcohol. For the preservatives, concentrations which were 2 times higher than recommended was used to examine their effect on precipitation. The mixtures with parabens or benzyl alcohol are shown in Figures 3 and 4, respectively. The mixtures of Sample No.4 and Sample No.12 with 0.1%, as well as 0.2% of parabens presented clear solutions, whereas the mixtures of Sample No.4 and Sample No.12 with 2% of benzyl alcohol showed slightly opaque solutions. The admixture solutions with benzyl alcohol became opaquer as the concentration of the preservative increased from 2% to 4%. These results suggest that the type of preservative used could have a marked effect on the compatibility of DEX and OND. Specifically, the results revealed that benzyl alcohol affected the compatibility of DEX–OND admixture solutions by triggering precipitation. In contrast, parabens even at twice the recommendation concentrations did not show any evidence of the precipitation of DEX–OND solutions.

Figure 3.

The various mixtures of preservatives with Sample No.4; NSS (A), Sample No.4 without preservatives (B), Sample No.4 with 0.1% parabens (C), Sample No.4 with 2% benzyl alcohol (D), Sample No.4 with 0.2% parabens (E), and Sample No.4 with 4% benzyl alcohol (F).

Figure 4.

The various mixtures of preservatives with Sample No.12; NSS (A), Sample No.12 without preservatives (B), Sample No.12 with 0.1% parabens (C), Sample No.12 with 2% benzyl alcohol (D), Sample No.12 with 0.2% parabens (E), and Sample No.12 with 4% benzyl alcohol (F).

Discussion

Combination antiemetic therapy is now considered mainstream for prevention of antineoplastic drug-induced vomiting and nausea in cancer patients. It is apparent that safe medication of patients could be ensured and enhanced by having proper insights into the compatibility of the drugs administered as mixtures. Until now, there has been a paucity of data on the effect of concentration on the physical and chemical compatibility of ondansetron and dexamethasone, administered as IV admixtures to counter nausea and vomiting in patients undergoing emetogenic chemotherapy. ⁶ This study extends the research state-of-the-art by studying the precipitation, particle size analysis and molecular interactions of ondansetron and dexamethasone at various concentrations. Herein, it was found that the concentration of both drugs effected the compatibility of the admixture. Moreover, the tendency for precipitation to occur was found to increase with increasing the amount of DEX in the admixture. The maximum amount of the respective drugs for which the DEX-OND sample did not present an opaque solution 8 mg and 16 mg in final volume of 50 ml of NSS. For DEX-OND sample prepared at 100 ml, the maximum amount of the respective drugs for which precipitation was not observed was 20 mg and 16 mg, respectively. In other words, there was a gain in the concentration of DEX as the volume increased from 50 to 100 ml (0.16-0.2 mg/ml); however, this gain came at the expense of OND which decreased from 0.32 to 0.16 mg/ml. Thus, in principle, the IV admixture at a final volume of 50 ml has a higher net concentration than at 100 ml. As such, for antiemetic drug treatment of cancer patients with hyperhydration monitoring during high dose chemotherapy preparation of IV admixture using the smaller volume of diluent (50 ml) would be more appropriate. ¹⁷ Additionally, the use of parabens as a preservative did not affect the IV admixture compatibility, whereas benzyl alcohol did. Therefore, the IV admixture of DEX and OND should be avoided if benzyl alcohol was used as a preservative in the commercial product.

Previous investigations had highlighted the impact of various parameters on the compatibility and stability of DEX and OND or other serotonin 5-HT₃ receptor antagonists IV admixtures, such as diluents,^6,18 storage conditions – container and temperature, ⁷ preservatives, ⁸ light exposure, ¹⁹ amongst others. The present work delineates in particular, the importance of the concentration of the individual components as well as the final volume on the compatibility of the IV admixture, thereby providing new insight relevant to the safe coadministration of these antiemetics.

Conclusion

The result from this study provides valuable information for the supportive care of patients receiving chemotherapy treatment. For patients with hyperhydration, the final volume of the antiemetic IV admixture and amounts of DEX and OND should be carefully considered in order to avoid precipitation from occurring. In the absence of fluid limitation for the patients, final admixture volume of 100 ml containing 20 mg DEX and 16 mg OND is appropriate. Conversely, in cases where there are fluid limitations such as in patients with hyperhydration and yet being highly dosed with emetic drugs, coadministration of 8 mg DEX and 16 mg OND in a final volume of 50 ml will be more appropriate. Finally, the type of preservative used in DEX and OND commercial products should be carefully considered.