The "What's That Stuff?" article on dental anesthetics may unfortunately lead some to the erroneous conclusion that cocaine and the so-called caine anesthetics are closely related (C&EN, June 29, page 33). The article claims that with names like benzocaine, some may think that these anesthetics must be derivatives of cocaine.
In turn, the misapprehension is created that commonly used dental anesthetics such as benzocaine may yield false positives in urine drug testing, indicating illicit use of cocaine. A cursory review of the structures for lidocaine, procaine, and articaine shows they lack the ecgonine nucleus. Furthermore, the common dental analgesics are not related to cocaine nor to its metabolites synthetically. In addition, cocaine and its derivatives are Federal Schedule II drugs, whereas procaine, lidocaine, and the other "caine" drugs are unscheduled.
During 16 years as the director of a Florida-licensed and federally certified employment-related drug-testing laboratory that also performed "driving under the influence of alcohol" and "driving under the influence of drugs" work for Florida's 20th judicial circuit, I (Robert White) had ample opportunity to refute many false reasons for a defendant or claimant to explain a confirmed positive "cocaine" urine drug test.
One of the most popular explanations was, "I went to my dentist and he gave me lidocaine. It must be the lidocaine that caused my positive for cocaine." This claim is predicated on the assumption that lidocaine mimics cocaine because both end in caine. It was proven in my lab and others' labs that ingestion of the caine drugs will not precipitate an immunoassay presumptive positive ("screening" result) for the major cocaine metabolite, benzoylecgonine (BE), the primary substance actually targeted by most cocaine immunoassays. In addition, gas chromatography/mass spectrometry (GC/MS) selected-ion monitoring for urine BE does not show any detectable peak for derivatized BE postingestion of drugs such as lidocaine. Similarly, analysis of the same urine for ecgonine methyl ester and parent cocaine by full-spectrum GC/MS reveals no peak for either substance postingestion. Thus, neither parent cocaine nor its metabolites are related to the caine drugs metabolically or immunologically.
In summary, the caine drugs such as lidocaine and procaine have their own structures separate from the ecgonine nucleus of cocaine and its derivatives and their own pharmacodynamic effects. The caine drugs are different both pharmacodynamically and pharmacokinetically, as well as legally, from cocaine. Thus, cocaine and the caine drugs should not be grouped together or confused with one another as that may lead to erroneous medicolegal conclusions that may be inferred from the cited article.
Robert M. White
Peter F. Eisenhart