Hospital Pharmacy - October 2019 - 331

331

Sabins et al
actual concentrations would be slightly lower due to bag
overfill and additive volume. The purpose of this study was
to evaluate the stability and compatibility of 0.2 and 1.0 mg/
mL diphenhydramine HCl admixtures in 0.9% sodium chloride injection and 5% dextrose injection in polyvinyl chloride (PVC) IV bags stored under refrigeration (2°C-8°C) for
up to 14 days.

Table 1. Forced Degradation Study of Diphenhydramine HCl.
Sample No.
1
2
3
4

Stress conditions

% drug remaining
after 24 hours

pH 2 and 60°C
pH 12 and 60°C
3% H2O2 and 60°C
3% H2O2 and sunlight

82.3
94.8
6.6
18.9

Methods
Materials for IV Admixtures
Diphenhydramine HCl Injection, USP, 50 mg/mL, and 1-mL
vials were purchased from Fresenius Kabi (NDC no. 63323664-16; lot no. 6011913; Lake Zurich, IL). The diluents used
to prepare the IV admixtures were obtained from 250 mL bags
of 0.9% Sodium Chloride Injection, USP, from Baxter (NDC
no.0338-0049-02, lot no. Y234302; Deerfield, IL) and 5%
Dextrose Injection, USP, from Baxter (NDC no.0338-001702, lot no. Y228320). Sterile empty 50 mL IV bags were not
available commercially at the time of the study. Therefore, 50
mL bags of 0.9% Sodium Chloride Injection, USP (NDC
no.0338-0049-31, lot no. P360990) and 5% Dextrose Injection,
USP (NDC no.0338-0017-11, lot no. P349647) were purchased from Baxter. The fluid in each 50 mL bag was completely removed under aseptic conditions prior to packaging of
the stability samples. The material of these bags was PVC.

Materials for High-Performance Liquid
Chromatography Analysis
A Milli-Q Direct 8 system from Millipore Sigma (Burlington,
Massachusetts) was used to produce Type I (ultrapure) water.
Acetonitrile and trifluoroacetic acid, both high-performance
liquid chromatography (HPLC) grades, were purchased from
Thermo Fisher Scientific (Waltham, Massachusetts).
Diphenhydramine HCl powder (99% purity) was purchased
from Acros Organics (Cat no. AC350850250, lot no.
A0370928; Pittsburgh, PA) and used as a reference standard
for HPLC calibration purpose.

Scientific Instruments (Marlborough, Massachusetts) was
equipped with a C18, 3 µm, 100 A, 4.6×150 mm column
from Phenomenex (Torrance, California) as the stationary
phase. The mobile phase consisted of water:acetonitrile
(63:37) with 0.1% trifluoroacetic acid, and the pH was
approximately 2.0. Additional instrument parameters were
set as follows: column temperature at 40°C, mobile phase
flow rate of 0.6 mL/min, sample injection volume of 5 µL,
and ultraviolet detection at 220 nm. Data collection and processing were performed by the Shimadzu LC Solution
software.
For calibration purpose, 5 standard solutions of diphenhydramine HCl (0.16, 0.18, 0.20, 0.22, and 0.24 mg/mL)
were run on each analysis day. This range encompasses the
80% to 120% of the expected concentration of the HPLC
samples. These standards were prepared from the pure
diphenhydramine HCl powder dissolved in water. A calibration curve was constructed on each analysis day by plotting
the peak area against concentration. The midpoint standard
of 0.20 mg/mL was also injected 3 times on each analysis
day to monitor the intraday and interday variability of the
HPLC method.

Forced Degradation Study

A Mettler-Toledo SevenEasy model pH meter (Columbus,
Ohio) was used with a gel-filled pencil-thin pH electrode
from Fisher Scientific (Cat no. 13-620-290). The pH meter
was calibrated daily with standard pH 4 and 7 buffer solutions purchased from Fisher Scientific (Cat no. SB101-500
and SB107-500).

A forced degradation study was performed to confirm that
the above HPLC method could separate the potential degradation products from the original drug. As listed in Table 1, 4
drug samples of 0.20 mg/mL were subjected to different
stress conditions of extreme pH, oxidizing agent, heat, and
light. Samples 1 and 2 were adjusted to pH 2 and pH 12 by
adding 1 M hydrochloric acid and 1 M sodium hydroxide,
respectively. Samples 3 and 4 were both spiked with concentrated hydrogen peroxide to a final concentration of 3%.
Samples 1, 2, and 3 were incubated at 60°C, and Sample 4
was exposed to direct sunlight at ambient room temperature.
All 4 samples were monitored by the HPLC analysis until a
minimum of 10% degradation was observed in at least 1 of
the 4 samples.10,11

HPLC Analysis

14-Day Stability Study of IV Admixtures

A reversed-phase HPLC method was developed for diphenhydramine to measure drug concentration and monitor drug
stability. A Model LC-2010A system from Shimadzu

Four IV admixtures of diphenhydramine were prepared for
this stability study which included 2 drug concentrations
(0.2 and 1.0 mg/mL) and 2 diluents (0.9% sodium chloride

pH Analysis

Hospital Pharmacy - October 2019

Table of Contents for the Digital Edition of Hospital Pharmacy - October 2019