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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 45, Number 7, September,
pp.419-421
LETTER TO THE EDITOR: Comments on “Incomplete
Recovery of Prescription Opioids in Urine using Enzymatic Hydrolysis
of Glucuronide Metabolites”
Wayne C. Duer[1] and Shallyn McFarland[2]
[1]Hillsborough County Medical Examiner Department, 401 South
Morgan Street, Tampa, Florida 33602 and Department of Pathology
and Cell Biology, College of Medicine, University of South Florida,
12901 Bruce B. Downs Boulevard, Tampa, Florida 33163 and
[2]Florida Department of Law Enforcement, North Lois Avenue,
Tampa, Florida 33614
The article “Incomplete Recovery of Prescription
Opioids in Urine using Enzymatic Hydrolysis of Glucuronide Metabolites”
by Wang et al. presents results that are in disagreement with
previous studies and makes inadequate attempts to explain these
differences. In light of the widespread use of enzymatic hydrolysis,
these differences deserve comment. Wang et al. reported that b≤-glucuronidase
from Escherichia coli (E. coli, Sigma Chemical, St. Louis, MO,
catalog #G7396) was not able to hydrolyze any morphine-3-glucuronide,
M3G, from a custom made quality control material at pH 6.8 (0.1M,
phosphate buffer) at 50ºC using 2500 Sigma U/mL in 16 h.
They further reported similar results for patient urine samples.
These findings are contrary to our experience and the experience
of others . Romberg and Lee found that essentially 100% of M3G
in urine was hydrolyzed with the same product as used by Wang
et al. (Sigma Chemical catalog #G7396) pH 6 to 6.5 (0.075M phosphate
buffer) at 50ºC using 1000 to 1500 U/mL in 3 h. Zezulak et
al. found that at least 90% of M3G in urine was hydrolyzed at
pH 6.8 (0.075M phosphate buffer) at 37ºC using 1200 U/mL
within 4 h. Hackett et al. found that in excess of 90% of M3G
in urine was hydrolyzed with the same product (Sigma catalog #G7396)
as used by Wang et al. at pH 6.7 (0.0333M phosphate buffer) at
45ºC using 3333 U/mL in 4 h. These conflicting results suggest
the presence of an unrecognized determinant error in the work
of Wang et al.
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