Can Dental Anesthesia cause False Positive Drug Tests?

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

 

Can any local anesthetics cause false positive drug tests?

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 urine.  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

Alcohol	7-12 h
Amphetamine	48 h
Methamphetamine	48 h
Barbiturate
Short-acting (e.g., pentobarbital)	24 h
Long-acting (e.g., phenobarbital)	3 wk
Benzodiazepine
Short-acting (e.g., lorazepam)	3 d
long-acting (e.g., diazepam)	30 d
Cocaine metabolites	2-4 d
Marijuana
Single use	3 d
Moderate use (4 times/wk)	5-7 d
daily use	10-15 d
Long-term heavy smoker	>30 d
Opioids
Codeine	48 h
Heroin (morphine)	48 h
Hydromorphone	2-4 d
Methadone	3 d
Morphine	48-72 h
Oxycodone	2-4 d
Propoxyphene	6-48 h
Phencyclidine	8 d

List of substances that can cause false positive urine immunoassays

There are lots of other problems with drug testing, especially as it relates to employee screening in today's large corporate structures.  False positives may be the result of a range of problems from cross reaction with over-the-counter and prescription medications, to systemic conditions such as diabetes, or kidney and liver disease. Plain sloppiness on the part of the testing facility may also be a factor.  

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.)

Substance tested via immunoassay	Potential agents causing false-positive result	Most common brand name, or use
Alcohol	Short-chain alcohols (e.g., isopropyl or Methyl alcohol)	Rubbing alcohol, Wood alcohol
Amphetamines	Amantadine	Symmetrel--Treats Asian flu (Anti-viral) and Parkinson's
	Benzphetamine	Didrex--diet drug
	Bupropion	Wellbutrin--antidepressant, also used to help stop smoking
	Chlorpromazine	Thorazine--phenothiazine used to treat schizophrenia
	Clobenzorex	Asenlix, Finedal, or Rexigen "greenies" treats Parkinson's
	Deprenyl	Carbex, Eldepryl--Treats Parkinson's
	Desipramine	Norpramin--Tricyclic antidepressant, also for sleep disorders
	Dextroamphetamine	Dexadrine (an anphetamine)
	Ephedrine	Decongestant, used in many brands of  cold medicine
	Fenproporex	Diet pill--Component of FenFen
	l-methamphetamine	Vicks Nasal Inhaler--Can cause false positive for methamphetamine
	Isometheptene	Used to treat migraines--component of Amadrine and Midrin
	Isoxsuprine	Vasodilan--Vasodilator used to treat dementia, Raynaud's and poor circulation
	Labetalol	Normodyne, Trandate--Beta Blocker--Blood pressure med
	MDMA	Ecstasy--illegal drug
	Methylphenidate	Concerta, Ritalin--Used for ADHD
	Phentermine	Diet pill--Component of FenFen
	Phenylephrine,Phenylpropanolamine, Promethazine, Pseudoephedrine	Decongests  used in nasal sprays and cold medicines
	Ranitidine	Zantac, treats acid reflux
	Ritodrine	Yutopar--Smooth muscle relaxant used to treat premature labor
	Selegiline	Eldepryl--MAO inhibitor used to treat Parkinson's
	Thioridazine	Mellaril--used to treat schizophrenia
	Trazodone	Antidepressant--treats sleep disorders
	Trimethobenzamide	Tigan, used to treat nausea
	Trimipramine	Surmontil--Tricyclic antidepressant
Benzodiazepines (like valium and Ativan)	Oxaprozin	Daypro--An NSAID similar to ibuprophen
	Sertraline	Zoloft--Treats depression and OCD
Cannabinoids (marijuana or THC)	dronabinol	Marinol-Manmade Cannabis used to treat Nausea in cancer patients
	Efavirenz	Sustiva--For treating HIV
	Hemp-containing foods	Mostly sold in health food shops
	NSAIDs	Advil, Motrin, Aleve--These OTC drugs treat pain and inflammation
	Proton pump inhibitors	Zantac, Pepsid, Prilosec, Prevacid, Protonix--Used to treat Acid Reflux disease
	Tolmetin	Another NSAID not often prescribed
Cocaine	Coca leaf tea	Illegal in USA
	Topical anesthetics containing cocaine	Cocaine is no longer used in dentistry, but is still used in eye drops in ophthalmology
Opioids, opiates, and heroin	Dextromethorphan	Cough suppressant found in Robitussin DM, Mucinex DM
	Diphenhydramine	Benedryl--An antihistamine found in sleep, allergy and cold meds
	Opiates (codeine,hydromorphone hydrocodone, morphine and Heroin, Oxycontin)	These are all opioids and are illegal without a prescription.
	Poppy seeds	Found in MANY food items--serious problem in urine immunoassay drug tests
	Quinine	An Antimalial agent
	Quinolones	A class of antibiotics including Cipro and Levaquin
	Rifampin	Rifadin--An antibiotic used for tuberculosis
	Verapamil and its metabolites	Isoptin, Verelan--Calcium Channel Blocker used to treat hypertension
Phencyclidine	Dextromethorphan	Cough suppressant-- Robitussin DM, Mucinex DM
	Diphenhydramine	Benedryl--An antihistamine found in sleep and cold meds
	Doxylamine	Aldex, Equate sleep aid--Antihistamine similar to Benedryl used as sleep aid
	Ibuprofen	Motrin, Advil
	Imipramine	Tofranil--Tricyclic antidepressant used to treat depression and sleep disorders
	Ketamine	Surgical anesthetic
	Meperidine	Demerol--an opiate similar to morphine
	Mesoridazine	Serentil--Similar to thorazine, used to treat schizophrenia
	Thioridazine	Mellaril--Similar to thorizine used to treat schizoprhenia
	Tramadol	A low grade opioid for pain relief available OTC in some countries
	Venlafaxine, O-desmethylvenlafaxine	Effexor--Antidepressant for major depression
Tricyclic antidepressants	Carbamazepine	Tegretol--An anticonvulsant used to treat epilepsy and atypical pain disorders
	Cyclobenzaprine	Flexeril--A skeletal muscle relaxant
	Cyproheptadine	Periactin--an antihistamine used to treat severe allergies
	Diphenhydramine	Benedryl--An antihistamine used to treat allergies and as a sleep aid
	Hydroxyzine	Vistaril, Atarax--Antihistamine--treats itches and nausea

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.  

Q. But I have a prescription for medical marijuana to treat chronic pain.  I live in a state in which such prescriptions are legal.  Can an employer legally fire me if I test positive for marijuana in my urine or blood?

A. YES, the employer can still fire you, even if you have a legal prescription for medical marijuana, or for any other drug that is illegal under federal law.  Even if state law makes a drug de facto legal, federal law trumps state law, and marijuana is still illegal according to federal statutes.  On another level, an employer may choose to terminate any employee if the employer suspects that the employee might be impaired on the job. 

Click here to be directed to a fairly good page explaining the ins and outs of drug testing.