Stability of Advanced Life Support Drugs in the Field

Mark A. Gill; Alice Z. Kislik; Lana Gore; Angela Chandna

Disclosures

Am J Health Syst Pharm. 2004;61(6) 

In This Article

Methods

Three sets of autoinjector-style syringes of atropine 0.1 mg/mL,a epinephrine 1:10,000,b and lidocaine 2%c were taken from stock for each paramedic vehicle selected. The product was checked to confirm an expiration date past the completion of this study (12 months). Triplicate control syringes were stored in the laboratory at controlled room temperature and shielded from light. One-milliliter samples were withdrawn from the syringes at time 0 and on days 5, 10, 15, 30, and 45. The samples were placed into polyvinyl microcentrifuge tubes and transported on ice to the University of Southern California, where they were stored at -94 °F (-70 °C). Vehicles for drug storage were selected from paramedic units located in locales with temperature extremes, including desert, marine, and helicopter-based divisions.

A palm-size, battery-powered temperature recorderd (Figure 1) with memory was used to track the temperature inside the drug storage compartment at 15-minute intervals. Each device had a fresh battery, was calibrated, and was checked for data download whenever drug samples were obtained. A flashing red light on each device indicated that battery power was sufficient. The intent was to analyze data to determine the frequency of exposure to temperatures beyond the USP standards of 59 to 86 °F (15-30 °C) and an MKT higher than 77 °F (25 °C).

Temperature-recording device.

The temperature data were downloaded onto a computer for a visual inspection of temperature spikes (Figure 2) and used in statistical analysis. If drug degradation occurs as a function of exposure time, the cumulative time exceeding 24 hours above 40 °C or an MKT higher than 25 °C, as suggested by USP, should constitute appropriate measures of the extent to which drug degradation is expected to occur.[1,6]

Recording of temperature fluctuations at 15-minute intervals for 45 days. Temperature (°F).

MKT was calculated in accordance with the method specified by USP,[1,7] which uses the following formula, derived from the Arrhenius equation:

MKT = (-ΔH/R) / (ln[(eH/RTI + eH/RT2) + ... eH/RTn /n])

where ΔH is the heat of activation (83.144 kJ/mol), R is the universal gas constant (8.3144 × 10-3 kJ/mol/°K), T is the average of the highest and lowest temperature values recorded during each time period and expressed in °K (we selected a time period of four hours), T1 is the average temperature for the first time period, T2 is the average temperature for the second time period, Tn is the average temperature for the nth time period, and n is the total number of time periods.

The drug under consideration was defined as being stable if the remaining drug concentration was above 90% of the original concentration without color changes or precipitation.

Atropine. The samples were thawed and injected undiluted onto the column.e The HPLC procedure was developed in our laboratory and used for all three assays. Atropine concentration in solution was determined at room temperature using an HPLC systemf equipped with an autosamplerg and a variable-wavelength ultraviolet-light detector,h all of which were connected to a data integrator.i The mobile phase consisted of 60:40 acetonitrile and phosphate buffer (prepared with 0.02 M potassium phosphate with 5 mM octanesulfonic acid as an ion pair and adjusted to a pH of 6 with sodium hydroxide). The flow rate was 1.5 mL/min. The ultraviolet-light detector was set with a wavelength of 226 nm. The injection volume was 50 µL with a retention time of 3.7 minutes.

A stock solution was created using analytical grade atropine sulfate at a concentration of 1000 µg/mL in distilled water and stored at -4 °F (-20 °C). Working standards were created using the above stock solution diluted to concentrations of 125, 100, 80, 70, and 60 µg/mL in water and stored under refrigeration. A 5-point linear standard curve was generated using the above solutions. The interday coefficients of variation (CVs) for the assay of atropine standard solutions were 3.1-3.8% (n = 8) and the intraday CVs were 0.8-3.2% (n = 3). Correlation coefficients for standard curves all exceeded 0.99. The area under the peak was used to determine the remaining drug concentration.

Epinephrine. The samples were thawed and injected undiluted onto the column.e Epinephrine concentration in solution was determined at room temperature. The mobile phase consisted of 15:85 acetonitrile and phosphate buffer (prepared with 0.01 M sodium phosphate with 10mM octanesulfonic acid as an ion pair and pH adjusted to 4.5 with phosphoric acid). The flow rate was 1.0 mL/min. The ultraviolet-light detector was set with a wavelength of 226 nm. The injection volume was 25 µL with a retention time of 4.4 minutes.

A stock solution was created using analytical-grade L-epinephrinek at a concentration of 1000 µg/mL in distilled water and stored at -4 °F (-20 °C). Working standards were created using the above stock solution diluted to concentrations of 125, 100, 80, 70, and 60 µg/mL in water and stored under refrigeration. A 5-point linear standard curve was generated using the above solutions. The interday CVs for the assay of epinephrine standard solutions were 2.4-3.6% (n = 9), and the intraday CVs were 0.4-2.9% (n = 3). All correlation coefficients for standard curves exceeded 0.99. The area under the peak was used to determine drug concentration.

Lidocaine. The samples were thawed and were injected undiluted onto the column.l Lidocaine concentration in solution was determined at room temperature. The mobile phase consisted of 60:40 acetonitrile and phosphate buffer (prepared with 0.02 M potassium phosphate with 5mM octanesulfonic acid as an ion pair and pH adjusted to 6 with sodium hydroxide). The flow rate was 1.5 mL/min. The ultraviolet-lightdetector was set with a wavelength of 254 nm. The injection volume was 25 µL with a retention time of 5.7 minutes.

A stock solution was created using analytical-grade lidocainem at a concentration of 100 mg/mL in distilled water and stored at -4 °F (-20 °C). Working standards were created using the above stock solution diluted to concentrations of 25, 20, 16, 14, and 12 mg/mL in water and stored under refrigeration. A 5-point linear standard curve was generated using the above solutions. The interday CVs for lidocaine standard solutions were 0.9-3.1% (n = 6), and the intraday CVs were 0.9-1.5% (n = 3). All correlation coefficients for standard curves exceeded 0.99. The area under the peak was used to determine drug concentration.

To determine the stability-indicating capability of each assay, the drug solutions were exposed to extreme basic, acidic, and heated conditions and observed for degradation products. Samples of atropine 100 µg/mL, epinephrine 100 µg/mL, and lidocaine 20,000 µg/mL were degraded by heating and exposure to 1 N sodium hydroxide and 1 N hydrochloric acid. Atropine and lidocaine were degraded by exposure to 1 N sodium hydroxide at 212 °F (100 °C) for two hours and 1 N hydrochloric acid at 212 °F (100 °C) for two hours. Epinephrine was degraded by exposure to 1 N sodium hydroxide at 212 °F (100 °C) for one hour and 1 N hydrochloric acid at 212 °F (100 °C) for three hours.

A new chromatographic peak occurred at 2.26 minutes for atropine degraded by either base or acid; 100% of the original atropine was degraded by the base and 95% of original atropine was degraded by acid. A new chromatographic peak occurred at two minutes for lidocaine degraded by either base or acid; the original lidocaine peak was reduced by 16%. A new chromatographic peak occurred at 6.7 minutes for epinephrine degraded by base and at 6.57 minutes when degraded by acid; 100% of the original epinephrine was degraded by either base or acid.

At no time did we detect interference of the parent drugs with degradation peaks. We concluded that the three assay procedures were stability indicating.

All solutions were observed for changes in color and turbidity throughout the experiment. A single observer visually inspected the samples using fluorescent lighting with both black and white backgrounds. Any color change, precipitation, or turbidity was considered abnormal.

aAtropine sulfate injection, USP, 0.1 mg/mL, Abbott Laboratories, North Chicago, IL, lot 53-050-dk.
bEpinephrine injection, USP, 1:10,000, Abbott, lot 44-204-dk.
cLidocaine HCl injection, USP, 2%, Abbott, lot 55-341-dk.
dDickson SL-100, Dickson, Addison, IL, lot 9211866.
eCyano column 5-µm, 4.5 × 250 mm, J&W Scientific, Folsom, CA, lot 5061412.
fHPLC system, L6200, Hitachi, Tokyo, Japan.
gAutosampler, AS2000, Hitachi.
hL4200 U-V detector, Hitachi.
iD-2500 Chromato-Integrator, Hitachi.
jAnalytical-grade atropine sulfate, United States Pharmacopeial Convention, Rockville, MD, lot L.
kAnalytical-grade epinephrine, ICN, Aurora, OH, lot 7389a.
lC-18 column, 5-µm, 4.5 × 250 mm, J&W Scientific, lot 5061412.
mAnalytical-grade lidocaine, Sigma Chemical, St. Louis, MO, lot 113H0387.

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