This is the last of seven pages which constitute a course in local anesthetics.  Each page stands on its own, however for a thorough understanding of dental local anesthetics the reader is advised to read the pages in order.

<==Allergies to local anesthetic

Local anesthetic injections before a drug test do NOT cause false positive results for cocaine in urine tests!    Urine testing for cocaine involves an immunoassay using antibodies against the major metabolites of cocaine, ecgonine methyl ester and benzoylecgonine.  These chemicals are  unique to the metabolism of cocaine and will not appear in the urine if the patient has been injected with lidocaine or other dental anesthetic. 

In order to manufacture the lab test kit, the manufacturer injects ecgonine methyl ester and/or benzoylecgonine into the veins of a large laboratory animal, such as a horse or a sheep.  The animal's immune system then naturally makes antibodies against them, and these antibodies circulate in the animal's blood.  The animal's blood is then drawn, and the antibodies are extracted from the plasma.  These antibodies are then refined and used in the testing kit to bind to the ecgonine metabolites in the testee's unine.  If the antibodies bind to their target metabolites, then the solution turns a specific color indicating a positive test.  According to expert opinion, cross reactivity between urine immunoassay screens for these metabolites and substances other than cocaine are nearly nonexistent! 

Other testing issues

Even though mainstream opinion confirms the infallibility of the immunoassay for cocaine, the same cannot be said for other drugs.  Immunoassays are not the best way to test for metabolites or the drugs themselves, even though they are the least expensive and most readily available type of urine test on the market.  The natural function of antibodies is to recognize proteins characteristic of viruses and bacteria.  While antibodies are good at recognizing large protein molecules, they are not as specific in recognizing especially small molecules.  Drug metabolites, as well as the drugs themselves have small molecular structures.  The argument against urine immunoassay testing suggests that the drug test kit manufacturer generally knows the rates of false positive results associated with any given batch of their test kits, although they are not often very forthcoming about this.  The rate varies depending on the specificity of the batch of antibody that accompanies the kit.

The ramifications of this are a bit complex.  The only definitive way to confirm that a positive urine test for cocaine (or any other drug) is actually due to recent exposure to the actual drug, and not to a substance which may produce a false positive result, is to perform another test called gas chromatography-mass spectrometry (GCMS) on the same sample.  If you have recently used cocaine or any other controlled drug, this test is irrefutable (provided that the test was run by a competent lab), but if your urine originally tested as a false positive due to the lack of specificity of the testing technique, or for any other reason, a GCMS will clear your name. 

Unfortunately, these tests are expensive, and a prospective employer is under no obligation to retest your urine, since he can refuse to hire you for any reason except those based on sexual or racial discrimination. 

On the other hand, if you already hold a job which you may lose due to a random drug test, or if there is a chance that the test might result in legal consequences beyond losing your job, then the employer or testing authority should run the more expensive GCMS test on the original sample to confirm your drug status.  If the employer refuses, or if he did not retain the original sample, then you may have an actionable legal case against the employer.

Length of time drug abuse can be detected in urine

The following is a list of illegal drugs, each followed by a number of commonly used and legally available substances (many of them prescription drugs) that may cross-react and cause a false positive drug test.

Note that the use of prescription (DEA schedule II, III, IV or V)  drugs without a doctor's prescription is illegal and are grounds for the legal consequences stemming from a positive drug test.  (Schedule I includes drugs such as heroine, LSD, ecstasy, designer and experimental drugs.   None of these are legal to prescribe to the general public.)

Drug testing: Your rights versus the employer

Employers are private individuals under the law.  They have a right to deny you employment for any reason (provided the reason is not based on racial or sexual discrimination).  This means that an employer's rights extend to demanding that a prospective employee agree not only to submit to a drug test before being hired, but also to signing an agreement that the employer may demand that the employee, once hired, must submit to drug tests on demand in the future.  

For their part, employers have been forced by modern litigation practices to take a hard line against any employee who uses drugs.  The mere presence of an employee who can be shown to be abusing illegal substances places that employer at huge risk of having to pay gigantic awards to a plaintiff and his lawyer.  If you are unfairly targeted for termination of employment due to drug testing, you have become a victim of the perversions of American tort law.

Much is made of the citizens' fourth amendment right to freedom from unreasonable search and seizure of person or property.  Unfortunately, this right applies only to federal or state cases in which a search may result in legal sanctions such as prison time or fines paid to the state.  Private parties such as an employee and an employer who have entered into a legal agreement requiring a search (the drug test) or a subsequent seizure (your job) based on the search are not covered by the fourth amendment.

While an employee drug test may result in the termination of the employee, and a prospective employee drug test (or refusal to submit to drug testing) may prevent a subject from being hired, these tests seldom result in state or federal charges being brought and therefore the subject's legal rights in these matters is fairly limited. Click here to be directed to a fairly good page explaining the ins and outs of drug testing.  

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