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The Tricks and Traps of Drug Testing

“Hey, I’ve got a drug test for a new job today. Is there anything I can take that will help me pass that drug test? I really need this job.” This is a fairly common question encountered by pharmacists. Simply receiving the question presents a moral dilemma, because of the contradictory desires to help the person conflicting with the knowledge that providing information will help this person continue an unhealthy lifestyle.

Many pharmacists do not know how to respond to this question because this topic was not part of their training.On the other hand, some pharmacists may be involved with addiction treatment programs. It is important to understand how patients may try to circumvent tests so they can look for these tricks.

Urine is the bodily fluid used most often to test for the presence of drugs. Urinalysis for the presence of drugs has the advantages of being relatively easy to obtain and very sensitive. Its limitations are that false positives sometimes occur and it can only detect drug use in the two to three days before the test.1,2 Since urine testing is the method used most commonly, it is also the method that receives most of the effort to thwart its effectiveness.

Despite the obvious need to supervise collection of urine samples, rigorous control of the collection process can be difficult. So there are many opportunities for the subject to contaminate the urine sample. There are many substances that are used to contaminate urine samples and most of them are readily available in the household.

The goal of contamination is usually to cause a false negative result. Dishwashing soap, sodium bicarbonate, table salt, denture cleaning tablets, bleach, drain opener, Visine and other substances have been used to adulterate urine samples. Most of them produce a false negative result when immunoassay techniques are used.3,4,5,6 Glutaraldehyde is an enzyme inhibitor that is sold as a commercial product (UrinAid) for urine sample adulteration.

When immunoassay techniques are used, glutaraldehyde can cause a false negative for many drugs of abuse, including amphetamines, benzodiazepines, cocaine, and opiates.2,7 A major disadvantage of adulterants is that they usually change the pH, appearance, or odor of the urine sample. If the adulterant is a powder, it might leave a visible residue in the bottom of the container. For this reason the physical characteristics of the urine sample should be assessed.

If it appears that the sample has been adulterated, it should be rejected.5,6 Another method is to randomly use gas chromatography-mass spectrometry (GC-MS) on urine samples. GC-MS is not affected by these adulterants and then subjects would know that they have a chance of being caught by a more accurate testing method.8,9

There are a lot of products being offered that claim to cleanse the body or flush drugs out of the body (Formula 1 De Tox Drink, Ready Clean, etc). They tend to consist of fruit or carbohydrate drinks fortified with vitamins. Instructions usually include drinking several ounces of water after using the cleansing product.

They claim to be able to cleanse the body of drugs and so the subject can pass a test within one hour. The sellers of these products also sell urine-testing kits, so that the effectiveness of the cleansing product can be proven before the real test. They say that they will refund up to double the amount spent on the product if it does not work.9,11 These products may work if the level of drug concentration is near the low end of the assay range.

However, simply drinking the amount of water they suggest appears to work about as well.12 The herbal remedy goldenseal is sometimes used orally to mask the presence of marijuana, cocaine, amphetamines, barbiturates, benzodiazepines, and phencyclidine.

It does not appear to be useful for this.13 In contrast to false negatives, there are some things that can produce false positive urine test results and, ironically, the possibility of false positives can be used as a defense. Poppy seeds cause urine to test positive for opiates, because they contain morphine.

This forms the basis for the well-known “Poppy Seed” defense when a positive urine test for opiates is obtained. However, there are ways to interpret the results of the urine test that defeat the “Poppy Seed” defense. If the urine concentration of morphine exceeds 5000 ng/mL, or the concentrations of codeine and morphine are found in a ratio of less than two, then poppy seeds are not the source.

If 6-mono-acetylmorphine, a metabolite of heroin, is found, again poppy seeds are not the source. Passive exposure is another excuse that is used for positive urine tests to marijuana, cocaine, and phencyclidine (PCP). However, the concentration of marijuana smoke required for passive exposure to result in a positive urine test result is nearly uninhabitable.

While cocaine is absorbed transdermally from smoke, the concentration does not exceed the lower limit of assay with passive exposure. Passive exposure to PCP causing a positive urine test is still conceivable.14 An isolated report suggests that gemfibrozil might cause a false positive test for marijuana.15

Amphetamines may appear in urine after taking cough medicine. Ephedrine, psuedoephdrine, and phenylpropanolamine (which is no longer sold) can appear in the urine and interfere with a urine test for amphetamine. Vicks Nasal Inhalers contain the l-isomer of methamphetamine and it can reach significant levels in urine depending upon the frequency of use.14 False positive defenses can be used to force another sample to be taken.

The subject of the test may be hoping that enough drug will be eliminated before the next test that it will not be positive. The websites that sell the cleansing products suggest that the subject deny using the substance if a urine test is positive and fall back on one of these false positive defenses.9

Hair Hair is being used with increasing frequency. Drugs or their metabolites can be detected in the shaft of hair or hair follicles. An advantage of hair sampling is that it is easier to obtain the sample in a method that is observable. Because the rate of hair growth is relatively predictable, where the drug appears along the hair shaft can be used to roughly gauge when drug use occurred and if drug use occurs on a regular basis.

A disadvantage of hair sampling is that it cannot detect an isolated episode of drug use that might have occurred only two or three days before the test. Hair sampling is used in detoxification programs.1 The same companies that sell products to defeat urine tests also sell products designed to interfere with drug tests in hair (Hair Follicle Shampoo, etc.).

They claim that the treatment will create heat to remove drug and its metabolites or to coat the hair and destroy illicit substances as they are released from the shaft during the analysis. It is not known how successful these products are, but the sellers recognize that it is more difficult to beat a hair drug test.9,11.

Saliva Using saliva is a relatively new way to screen for drug use. It has the drawback that it is only valid for a few hours after using opiates and marijuana.16 Saliva might be useful as an alternative to urine testing. If the subject is prepared for a urine test, using a saliva test might surprise them enough to thwart their plans.

But, as expected, there are products designed to evade saliva tests as well. These products (Saliva Cleanse, Saliva Mouthwash, etc.) are supposed to work by decreasing the production of saliva.

Breath The volatile nature of alcohol makes breath tests for its use feasible. Because many mouthwashes contain ethanol, their use has become a part of a false positive defense. However, the mouthwash must be used within minutes of the alcohol breath test to cause a false positive effect. With this in mind, subjects might carry of bottle of mouthwash in the car and claim that a positive alcohol test is due to the recent use of the mouthwash.

A higher concentration of alcohol in the mouthwash extends the period of time that a false positive might be expected. Listerine, Scope, and Lavoris have high concentrations of alcohol.17

Sweat Detoxification programs are now using sweat collection patches (PharmChek, Pharmchem, Menlo Park, CA; www.pharmchem.com) to monitor for drug use. The technique involves having the patient wear a sweat-collecting patch for a week. Drugs and metabolites appear in sweat fairly rapidly after ingestion.

Since the sweat accumulates in the patch, any drug use during the week is detected. This method can be used for marijuana, cocaine, opiates, stimulants, PCP and ecstasy. An advantage is that the monitoring is continuous for the week that the patch is worn. A disadvantage is that the actual wearing of the patch is not observed.1,18,19 So if the patient finds a way to remove the patch without detection, it will not detect drug use during that time period.

Commentary False negatives. False positives. There are many factors that can confuse the picture of drug testing. More than just helping a person continue with a dangerous activity, knowledge of these factors can help to predict what might happen after a drug test result is returned. It can help to interpret the results and look for telltale signs of trickery.

A key thing to remember when you get that question is that it may present a counseling opportunity about the dangers of using illicit drugs. It may also be an opportunity to help a person who is participating in an addiction recovery program be aware of prescription and over-the-counter products that may cause a false positive. Of course when you receive the question about how to get around a drug test, the best response is to not use drugs.

References

1. Kintz P, Tracqui A, Jamey C, Mangin P. Detection of codeine and phenobarbital in sweat collected with a sweat patch. J Anal Toxicol 1996;20:197-201.

2. George S, Braithwaite RA. The effect of glutaraldehyde adulteration of urine specimens on Syva EMIT II drugs-of-abuse assays. J Anal Toxicol 1996;20:195-6.

3. Schwarzhoff R, Cody JT. The effects of adulterating agents on FPIA analysis of urine for drugs of abuse. J Anal Toxicol 1993;17:14-7.

4. Stolk LM, Scheijen JL. Urine adulteration with denture-cleaning tablets. J Anal Toxicol 1997;21:403.

5. Mikkelsen SL, Ash KO. Adulterants causing false negatives in illicit drug testing. Clin Chem 1988;34:2333-6.

6. Warner A. Interference of common household chemicals in immunoassay methods for drugs of abuse. Clin Chem 1989;35:648-51.

7. Goldberger BA, Caplan YH. Effect of glutaraldehyde (UrinAid) on detection of abused drugs in urine by immunoassay. Clin Chem 1994;40:1605-6.

8. Notarianni LJ, Belk D, Collins AJ. False positives and negatives in routine testing for drugs of abuse. Lancet 1995;345:1115.

9. Huestis MA, Mitchell JM, Cone EJ. Detection times of marijuana metabolites in urine by immunoassay and GC-MS. J Anal Toxicol 1995;19:443-9.

10. I PASSED MY DRUG TEST.COM Website. http://www.ipassedmydrugtest.com. (Accessed January 21, 2003).

11. Clear Choice of New York Website. http://www.clearchoiceofny.com. (Accessed January 22, 2003).

12. Coleman DE, Baselt RC. Efficacy of two commercial products for altering urine drug test results. J Toxicol Clin Toxicol 1997;35:637-42.

13. Jellin JM, Gregory P, Batz F, et al. Pharmacist’s Letter/Prescriber’s Letter Natural Medicines Comprehensive Database. Stockton, CA. Therapeutic Research Faculty. http://www.naturaldatabase.com. (Accessed January 22, 2003).

14. elSohly MA, Jones AB. Drug testing in the workplace: could a positive test for one of the mandated drugs be for reasons other than illicit use of the drug? J Anal Toxicol 1995;19:450-8.

15. Lewis JH. Interference of Gemfibrozil with Roche TesTcup. J Anal Toxicol 1999;23:384.

16. Jehanli A, Brannan S, Moore L, Spiehler VR. Blind trials of an onsite saliva drug test for marijuana and opiates. J Forensic Sci 2001;46:1214-20.

17. Modell JG, Taylor JP, Lee JY. Breath alcohol values following mouthwash use. JAMA 1993;270:2955-6.

18. PharmChem Website. http://www.pharmchem.com. (Accessed January 21, 2003).

19. Kintz P. Drug testing in addicts: a comparison between urine, sweat, and hair. Ther Drug Monit 1996;18:450-5.