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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 25,
Number 6 September 2001, pp. 443-449
In Vitro
Reaction of Barbiturates with Formaldehyde
Peter
M. Gannett†, Jonathan R. Daft, Devona James, Blanche Rybeck, James B. Knopp,
and Timothy S. Tracy
West Virginia University, School of Pharmacy, Basic Pharmaceutical Sciences,
P.O. Box 9530, Morgantown, West Virginia 26506
Barbiturates
are widely used as sedatives, hypnotics, and antiepileptics, and, when coupled
with their narrow therapeutic index, the probability that their use will result
in accidental or intentional death is significant. When barbiturates are implicated
in a murder or suicide, analysis for their presence is often required. Under
certain conditions, barbiturates are quite stable, but conditions found in
vivo immediately after death or after embalming may promote barbiturate decomposition.
If extensive decomposition occurs, analysis for them may be difficult or impossible.
Here, the stability of three representative barbiturates, under conditions
that model those likely to prevail in vivo shortly after death and after embalming,
have been studied. Solutions of phenobarbital were found to slowly decompose
in water over the pH range of approximately 3.5 to 9.5. More rapid decomposition
occurred at higher pH, and 2-phenylbutyric acid was the main decomposition
product. Formaldehyde (5–20%) accelerated the decomposition rate 3–10-fold
such that phenobarbital decomposition could be complete after 30 days. In
contrast, pentobarbital decomposed roughly 10 times more slowly and secobarbital
did not detectably decompose under any of the conditions studied. Thus, certain
barbiturates may partially or completely decompose in vivo after death, especially
after embalming, and thus analysis for them may lead to false negatives. However,
this work shows that analysis for the parent barbiturate or its predicted
decomposition product may provide data that will reduce the likelihood of
false negatives.
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