Abstract
Purpose:Evaluate the stability of isoproterenol hydrochloride injection in 0.9% sodium chloride in polyvinyl chloride bags for up to 90 days. Methods: Dilutions of isoproterenol hydrochloride injection to a concentration of 4 μg/mL were performed under aseptic conditions. The bags were stored in amber ultraviolet light blocking bags at room temperature (23°C-25°C) or under refrigeration (3°C-5°C). Three samples of each preparation and storage environment were analyzed on days 0, 2, 14, 30, 45, 60, and 90. Physical stability was performed by visual examination. The pH was assessed at baseline, each analysis day, and upon final degradation evaluation. Sterility of the samples was not assessed. Chemical stability of isoproterenol hydrochloride was evaluated using liquid chromatography with tandem mass spectrometry. Samples were considered stable if there was <10% degradation of the initial concentration. Results: Isoproterenol hydrochloride diluted to 4 μg/mL with 0.9% sodium chloride injection was physically stable throughout the study. No precipitation was observed. At days 2, 14, 30, 45, 60, and 90 all bags diluted to 4 μg/mL had <10% degradation when stored under refrigeration (3°C-5°C) or stored at room temperature (23°C-25°C). Conclusion: Isoproterenol hydrochloride diluted to a concentration of 4 μg/mL with 0.9% sodium chloride for injection in ultraviolet light blocking bags was stable for 90 days at room temperature and under refrigeration.
Keywords: isoproterenol, beta-agonist, drug waste, sodium chloride, drug stability
Introduction
Isoproterenol hydrochloride is a sympathomimetic agent and replicates the actions of the sympathetic nervous system. 1 Its potent β1 and β2 agonist properties lead to vasodilation and increase cardiac inotropy and chronotropy. 2 Due to these effects, isoproterenol hydrochloride is commonly used for cardiac rhythm support during episodes of profound bradycardia or cardiac arrest. Isoproterenol hydrochloride is also used widely during cardiac electrophysiology testing and ablation procedures.3 -6 Isoproterenol hydrochloride can be administered as an intramuscular injection, an intravenous bolus, or an intravenous infusion. Concentrated isoproterenol hydrochloride, typically in a 0.2 mg/mL concentration, must be further diluted for intravenous administration. Isoproterenol hydrochloride for intravenous infusion is commonly diluted to concentrations ranging from 2 to 4 µg/mL. 1
Isoproterenol contains a catechol moiety which is susceptible to oxidative reactions catalyzed by ultraviolet light, oxygen, increases in temperature, and basic conditions. 7 Efforts to mitigate these degradation mechanisms include temperature control, minimizing air introduction during compounding, and storage of compounded solution within amber ultraviolet light blocking bags. Previous stability studies have shown isoproterenol hydrochloride at concentrations from 2 to 4 µg/mL is stable for up to 24 hours within polyvinyl chloride bags at room temperature and under refrigeration. 8 However, no stability-indicating studies have evaluated the stability of isoproterenol hydrochloride in polyvinyl chloride bags for greater than 24 hours.
The purpose of this study was to determine the physical and chemical stability of isoproterenol hydrochloride at concentrations of 4 µg/mL in 0.9% sodium chloride when stored at room temperature or refrigerated for 90 days while in amber ultraviolet light blocking bags.
Methods
Sample Preparation
Dilution of isoproterenol hydrochloride (Isoproterenol hydrochloride injection, 1 mg/5 mL, 5 mL vial, Valeant Pharmaceuticals North America LLC; Bridgewater, NJ lot 701653F) to a nominal concentration of 4 μg/mL was performed by the University of Colorado Hospital pharmacy under aseptic conditions in an International Standards Organization class 7 environment by adding 1 mg isoproterenol hydrochloride (1 mg/5 mL) to 245 mL 0.9% sodium chloride for injection (0.9% sodium chloride for injection, 250 mL in polyvinyl chloride bag, Baxter Healthcare Corporation, Deerfield, IL, lot Y249896). Accurate volumes were achieved by removing all 0.9% sodium chloride for injection from all polyvinyl chloride bags and exact volumes of 0.9% sodium chloride for injection were then injected into the polyvinyl chloride bags utilizing a graduated syringe. This preparation was repeated 6 times for each concentration. The prepared solutions were then placed in amber ultraviolet light blocking bags (Amber UV Protection Zippit® Bags, Health Care Logistics, Circleville, OH). These preparations were then refrigerated (3°C-5°C) or stored at room temperature (23°C-25°C) under normal florescent lighting. Refrigerated samples were allowed to warm to room temperature before sampling. No external source of heat was used to warm the bags. Three bags for each of the storage conditions were assessed for physical and chemical stability over 90 days. Stability was assessed on days 0, 2, 14, 30, 45, 60, and 90. Sterility of the samples was not assessed.
Physical Evaluation
Physical stability of isoproterenol hydrochloride was assessed by visual examination. Solutions were evaluated against black and white backgrounds for visible particulate matter, cloudiness, and color change. The pH was assessed on day 1 and at each time of high-performance liquid chromatographic analysis, utilizing a pH electrode and meter (Orion 2-star pH Benchtop Meter, Thermo Scientific, Beverly, MA).
High-Performance Liquid Chromatographic Analysis
Isoproterenol concentrations were determined by liquid chromatography with tandem mass spectroscopy (LC/MS-MS; Sciex 4000 LC-MS/MS, Applied Biosystems, Waltham, MA). The system was equipped with a HPLC (Shimadzu HPLC, Shimadzu Scientific Instruments, Columbia, MD) and auto-sampler (PAL auto-sampler, LEAP Technologies, Carrboro, NC). LC/MS-MS methods: Liquid chromatography employed a C18 (Zorbax extended-C18 50 × 4.6 mm, Agilent Technologies, Santa Clara, CA) column set at 40°C with a flow-rate of 0.4 mL/minute. The mobile phase consisted of A: 10 mM ammonium acetate(NH4OAc), 0.1% formic acid in water (H2O), and B: 50:50 acetonitrile:methanol (ACN:MeOH). The chromatography method used was 95% A for 1.0 minutes; ramped to 95% B at 3.0 minutes, held for 7.0 minutes, and then brought back to 95% A at 13.0 minutes and held for 2.0 minutes (15 minutes total run time) (Figure 1). Two multiple reaction monitoring (MRM) transitions were monitored, MRM 212.15 → 193.91 m/z (collision energy [CE] = 17, collision cell exit potential [CXP] = 14) and MRM 212.15 → 151.93 m/z (CE = 25, CXP = 10).
Figure 1.
Representative LC/MS-MS.
Chromatogram area under the peak was used to determine isoproterenol hydrochloride concentrations. All samples for each storage condition were assayed in triplicate. Calibration of the HPLC system was performed by construction of a standard curve using 11 known concentrations of isoproterenol hydrochloride (range, 0-100 μg/mL) and was conducted on each of the study days. Coefficients of determination (r2) for the standard curve were greater than .95 for the entire study. Our assay met the best practice standards set for bioanalytical method validation. 9
To demonstrate the stability-indicating nature of the assay, degradation studies were performed at room temperature with exposure to fluorescent light. Isoproterenol was dissolved (100 μg/mL) in deionized distilled water and placed in a sample vial. After 24 hours, a sample was analyzed by HPLC/UV (Figure 2).
Figure 2.
Figure shows isoproterenol peak at 8.25 minutes with degradation peak occurring at 11 minutes. Isoproterenol begins to degrade immediately in the absence of preservative.
Stability Analysis
The percentage of isoproterenol hydrochloride remaining at each time point was determined. Samples were considered stable if there was less than 10% degradation of the initial concentration.
Results
Isoproterenol hydrochloride diluted to 4 μg/mL with 0.9% sodium chloride injection was physically stable throughout the study. Solutions kept under refrigeration or at room temperature remained clear throughout the study. No precipitation was observed. The mean ± SD concentration μg/mL of the room temperature concentration at baseline was 4.00 ± 0.01, Day 30 was 3.95 ± 0.01, Day 45 was 4.08 ± 0.03, Day 60 was 4.36 ± 0.02, and Day 90 4.01 ± 0.01. The mean ± SD pH of the refrigeration concentration at baseline was 3.91 ± 0.01, Day 30 was 4.08 ± 0.01, Day 45 was 3.86 ± 0.01, Day 60 was 3.99 ± 0.01, and Day 90 3.92 ± 0.02.
The results of the MS analysis are shown in Table 1. Minimal degradation was seen in both storage conditions and isoproterenol hydrochloride concentrations at day 30 and less than 10% degradation was seen at Day 90 for both concentrations and storage conditions. No new degradation peaks were observed, and concentrations of the unidentified peaks did not increase.
Table 1.
Stability of Isoproterenol Hydrochloride in 0.9% Sodium Chloride Injection.
| Isoproterenol concentration | Storage conditions | % initial concentration remaining | ||||||
|---|---|---|---|---|---|---|---|---|
| Day 0 | Day 2 | Day 14 | Day 30 | Day 45 | Day 60 | Day 90 | ||
| 4 µg/mL PVC Bag | Room temperature | 3.99 ± 0.1 µg/mL | 99.8 ± 4.5 | 101.3 ± 4.4 | 98.7 ± 3.0 | 102.0 ± 8.5 | 109.1 ± 5.8 | 100.4 ± 3.4 |
| Refrigeration | 3.91 ± 0.07 µg/mL | 100.4 ± 1.4 | 101.7 ± 1.2 | 104.4 ± 3.7 | 98.7 ± 1.2 | 102.1 ± 2.3 | 100.4 ± 4.4 | |
Discussion
The manufacturer of isoproterenol hydrochloride recommends unopened vials of isoproterenol hydrochloride be stored at controlled room temperature. 1 Compounded isoproterenol hydrochloride solutions should be stored in ultraviolet light blocking bags. This is an essential storage step to ensure stable isoproterenol hydrochloride concentrations by minimizing oxidation of the catechol functional group. 1 To the authors knowledge no current data is published utilizing a stability-indicating methodology regarding isoproterenol hydrochloride stability in 0.9% sodium chloride. The present study showed that all refrigerated bags retained greater than 90% isoproterenol hydrochloride concentration out to 90 days and all room temperature bags retained greater than 90% isoproterenol hydrochloride concentration out to 90 days. Overall, the mean concentration in all storage conditions was >90% of the original concentration at 90 days for all storage conditions. Despite this extended stability for 90 days based on product environment, the sterility of the prepared isoproterenol hydrochloride solution must be assessed according to the standards in chapter 71 and chapter 797 of the United States Pharmacopia. 10
Given the increase in isoproterenol hydrochloride cost of greater than 500% since 2015, hospital administrators have sought ways to reduce the impact of isoproterenol hydrochloride on overall drug expenditures. One hospital has implemented a daily batching process based on projected clinical need to minimize waste. This process without utilizing extended dating techniques has resulted in a cost savings of more than $600 000 in a 1-year period.2,11 This stability study allows for a 90-day room temperature or refrigeration shelf life if USP 797 requirements are followed. Isoproterenol hydrochloride bags can be batched centrally and placed within automated dispensing cabinet at desired locations or stored in satellite pharmacies within the facility. This proximity to the patient allows for the clinical team to have rapid access to isoproterenol hydrochloride infusions, reducing the amount of time to drug administration. The ability to batch isoproterenol hydrochloride may possibly reduce drug waste and medication errors due to improper dilution of the drug.
Conclusion
Isoproterenol hydrochloride diluted to a concentration of 4 μg/mL with 0.9% sodium chloride injection in ultraviolet light blocking bags was stable for 90 days at room temperature and under refrigeration.
Footnotes
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.
ORCID iD: Edward T. Van Matre 
https://orcid.org/0000-0001-9125-9509
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