Can Legal Drugs Cause a False Positive?

There are more than 250 over-the-counter medications and prescription drugs that could cause a false positive.

Filling out the lab test form to include over the counter medications that cause the same positive results as the illegal drug that might be consumed would be a good idea. If a positive result occurs on the test, a basis will have been laid for an appeal. Remember that the negative error rate is just as large or larger than the positive error rate. Many people using drugs escape detection.

Pain relievers such as Advil, Nuprin, Motrin, Midol, Trendar and Ibuprofen are known to cause false positives for Marijuana use. Secondhand smoke inhalation from a rock concert or from being with someone who is smoking marijuana could also cause a false positive for THC. Hemp seed products, such as hemp burgers or food products containing hemp oil will also cause false positives for THC. Twelve ounces of hemp seed products ingested before a test will cause you to fail your test and has held up as a defense in at least two federal court cases.

Dristan Nasal Spray, Neosynephren, Vicks Nasal Spray, Sudafed and other medications containing ephedrine or phenypropanolamine could cause a false positive reading for Amphetamines.

Vicks Formula 44M containing Dextromethorphan, and Primatene-M containing perylamine as well as the pain reliever Demerol, Quinine water, poppy seeds and prescription anti-depressant Elavil will cause a false positive for opiates.

Nyquil Nighttime Cold Medicine will cause a false positive for Methadone.

Antibiotics such as Ampicillin and Amoxicillin will cause a false positive for cocaine.

Diasepam as well as Dextromethorophan (an ingredient in some cough medicines) will cause a false positive for PCP.