False Positives on Drug Tests, page 143

False Positives Forum

This forum is intended to help those who Do NOT Abuse Drugs. We do NOT support the illegal use of any substance. If you have experience with false positives, share your experience. What would you tell someone about drug testing and false positives? Please remember that we do not give medical or legal advice.

Subj: Amoxicillin?
Date: 7/22/2011
Can amoxicillin give positive results for cocaine on drug test? I’ve never used cocaine.


AskDocWeb: Yes, amoxicillin is on the list. Fortunately a GC/MS confirmation test eliminates this type of false positive.

Subj: Hydrocodone not showing up on a drug test
Date: 7/24/2011
I have been taking one daily 5-500-pill of hydrocodone for a few yrs. I took a urine test 3 weeks ago and it turned up negative! Now my Dr. doesn’t think I’m taking them yet they are the only med that takes the edge off my extreme, undiagnosed, headaches. I don’t understand how? Please help w/ any answers. Thanx!


AskDocWeb: It is possible that too much of your last dose was out of your system by the time they did the urine test. The body eliminates hydrocodone rather quickly. Since the half-life is only 3.8 hours, most of it would be out of your system within 8 to 10 hours.

Subj: Drug test came back positive
Date: 7/25/2011
I am a Type 2 Diabetic, taking both Metformin and Glyberide, also taking Amlodipine for high blood pressure. For employment I just took a drug test and it came back positive. I have not taken any drugs other than what is prescribed. Can the prescribed medications have caused a false positive reading? I am contesting the drug test results, but can’t find anything to substantiate my claim.


AskDocWeb: There are a few sources listed here that may help you. See reference numbers 3, 16, 20, and 21. This is one of those subjects that seem to be taboo as far as research goes. The desire to help those with diabetes who get a false positive is far outweighed by the fear of appearing to aid drug abusers. It is not known whether the false positives in those with diabetes are caused by the condition or the drugs used to treat it.

Date: 7/25/2011
I’ve been trying to access your AskDocWeb false positive (Substances that cause False Positives) list, but it keeps locking up my computer, can anything be done? I’m involved in a court case because of taking Methyldopa & Labetalol and testing positive for amphetimines, so I need to be able to access this ASAP. Thank you,


AskDocWeb: If you are on a dial-up connection it can take awhile to load because it is such a large list. We do not use pop-ups or any kind of software that would lock up a computer so it may be something on your machine. Have you checked for malware recently?

Labetalol has not been reported to cause a false positive for amphetamines but there are antidotal reports of methyldopa sometimes showing up as a false positive for amphetamines. Methyldopa (Aldomet) does have many features similar in structure to an amphetamine. It appears similar enough to raise the possibility that a screening assay might pick it up as a false positive for amphetamine. Unfortunately there is no documentation to support that possibility. Are you able to get a GC/MS confirmation test?

Subj: Ruining lives and locking up innocent people
Date: 7/26/2011
18th judicial in Colorado is corrupt crooked and unconstitutional and rmoms enjoy ruining lives and locking up innocent people over false positive and non confirmed drug tests. guilty until proven innocent. I am going to make big waves as innocent people are ruined due to this corrupt judicial system in rich ass Colorado.


Subj: Doxylamine?
Date: 7/26/2011
Hi, I take Doxylamine succinate on a regular basis & recently tested positive for benzos….but I’ve never even heard of them!! Could the doxylamine give me a false positive?


AskDocWeb: Doxylamine has been reported to sometimes show up as a false positive for PCP or angel dust however, there are no reports of it showing up as benzodiazepine.

Subj: Adderall
Date: 7/26/2011
i would like to know if adderall is in the same category as cocaine and will it show up on a blood test as in the same category or different category.


AskDocWeb: Adderall will show up in a blood test but not as cocaine. Both are classified as Class II Narcotics. Adderall is a combination of dextroamphetamine and 4 amphetamine salts.

Subj: I am getting hassled
Date: 7/27/2011
I am a methadone patient and I’m given a U/A once each month. This past U/A test showed that I am (was) *positive* for secobarbital; I tested for that once before, but my manager at the clinic said she found that secobarbital is used in some OTC laxatives or stool softeners? I don’t know if that’s true, but she was fine w/that and so was I.

Today, there is a different manager and I am getting hassled and made to feel really low about secobarbital showing up a 2nd time in my June 2011 U/A. The ONLY barbiturate I take is Fiorinal (Aspirin, NO codeine); I’ve been trying to find, for hours now, whether or not Butalbital can and will false-positive as Secobarbital. On Erowid.org, a statement is made that Fiorocet, Fiorinal and Dilantin will show a false-positive as Secobarbital. Is this true? If it is true, this will be in my favor, so if you could please write back to me w/your actual name and contact info that would be awesome so I can print your reply and take it as my reliable source to the clinic so they will stop hassling me about this secobarbital business once and for all. Thank you so much for your time!


AskDocWeb: The best source references for proving something like this are the people who manufacture and distribute the drug testing kits. We found two that may help you out, Redwood Toxicology Laboratory Inc. and the Blue Grass Drug Screen company.
Redwood Toxicology Laboratory Inc. (RTL), is one of the nation’s premier forensic drug testing facilities. The results of their drug testing provide legally defensible results. RTL also sells millions of instant urine tests and oral fluid drug tests each year. Their website has a PDF file called Cross Reactions that shows both Butalbital and Fioricet may test positive for Barbiturates. For questions about their screening devices call 877-444-0049 or 707-571-1157 during regular business hours.

The other source reference is Blue Grass Drug Screen, Inc. Their iCup testing device is used by:

  • Military – Drug testing
  • Manufacturers – Pre-employment drug test, random drug test, and post accident drug testing.
  • Businesses – Drug Free Workplace testing programs.
  • Occupational Medical Facilities
  • Drug treatment facilities and Rehabilitation
  • Probation and Parole drug testing
  • Correctional Facility drug testing
  • High Schools – Drug testing high school athletes.

Their PDF file shows a Cross Reaction Chart of drugs that may cause problems with their test results. Problematic results are listed in red. They also have a toll free number: 1 (866) 323-7336.

Secobarbital (secobarbital sodium, Seconal, red devil) is a barbiturate that is used as a sodium salt for sedation and to treat convulsions.

Subj: My family don’t believe me
Date: 7/28/2011
I am in drug court and take at least 3 drug screens per week. I was recently hospitalized for severe bleeding ulcers. I was given demerol for pain and 4 doses of a g I cocktail, pheregan andzolphram in the hospital. When I was released I was given carafate, prednisone, zantac then they changed me to nexium and phenegan and took tylenol for pain. 7 days after I was released I failed 3 drug screens for barbituates. I had to spend 10 days in jail for this but want to prove to my family that I am not lying, that something I was given in the hospital caused this result please help me out. I haven’t taken anything except what I was given in the hospital since February but my family dont believe me.


AskDocWeb: Even if you proved that a false positive was possible, that is NOT proof that your test result was a false positive. For that you would need to get a GC/MS confirmation test.

Subj: Amoxicillin and other antibiotics
Date: 7/28/2011
Why do amoxicillin and other antbitics make you come positive for cocaine. Also do levaquin make you dirty as well?


AskDocWeb: When the body metabolizes a drug the end products it produces are called metabolites. (the word metabolites also has other meanings) These are the byproducts of the drug passing through your system and this is what drug tests are testing for. Some antibiotics produce metabolites that are similar to the metabolites produced by drugs of abuse. When this happens, a false positive may result. This occurs in only a small percentage of tests but it has happened. Levaquin (Fluoroquinolone) may show up on a urine test as a false positive for opiates.

Subj: I failed a drug test
Date: 7/29/2011
I have to drug test for drug court and they have a very elaborate expensive testing system. I went to court today and they claim I failed a drug test for amphetamines and barbiturates. It was apparently one test and 2 days later I passed the test. The ONLY thing I have taken is B-12 vitamins and 5 hour energy drinks. I had them send my test off but if it still comes back positive I will have to go to jail for over a week which can’t happen because I have a 5 month old son who needs me at home. Could either of these things be why I’m testing positive and why would I pass a test 2 days later??


AskDocWeb: One possible reason for testing clean 2 days later is that your body eliminated whatever was in your system that caused the first test to be positive. The only vitamin that has shown up on urine drug tests is B-2, not B-12. As for the 5-hour energy drinks, several people have claimed to get a false positive after using but we have not been able to document that. If they sent your sample for confirmation testing and it was a false positive then you should be okay.

Subj: Tested positive for amphetamines
Date: 7/29/2011
I’m 16 weeks pregnant, tested positive for amphetamines twice. However I do NOT take any sort of amphetamines, not street, prescribed or OTC. Why am I testing positive when all I take is Aldomet, iron supplement, and prenatal pills? I dont understand… I’m very upset about this & every time I go to my gyn everybody that works there looks at me funny. But like I said, I don’t take any drugs and I’m pregnant. I’m speechless don’t even know how to explain it.


AskDocWeb: If it just happened once then it may have been a defective test kit or an error on the part of someone doing the testing. If it happened more than once then you may want to take a serious look at this list for possible causes.

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