A false positive is defined as a drug free sample falsely being reported as positive for drugs. This can occur for a number of reasons including: improper laboratory procedure, mixing up specimen samples, incorrect paperwork, and passive inhalation. But the most common cause of false positives are cross reactants. A cross reactant is a substance which, because of its similar chemical structure to a drug or its metabolite, can cause a false positive result. The following substances can cause cross reactivity on an Immunoassay screen but are unlikely to be mistaken on a Gas Chromatography/Mass Spectrometry test:

Note: Additional Information can be found in our Drug Testing Books section.

THC (MARIJUANA)

Over-the-Counter NSAIDs:
Ibuprofen, Advil, Nuprin, Mediprin, Motrin, Bayer Select Pain Relief Formula, Excedrin IB Caplets, Genpril, Midol 200, Pamprin, Trendar Cramp Relief Formula, Cramp End Tablets, Medipren, Rufin, Naproxen, Aleve, Keroprofen, Orudis KT.

Prescription NSAIDs:
Anaprox, Tolectin, ifenoprofen, fluriprofen, oxaprozin, Ansaid, Clinoril, Dolobid, Feldene, Indocin, Lodine, Meclomen, Nalfon, Naprosyn, Orudis, Relafen, Voltaren

Prescription Allergy/Anti-Nausea Meds:
Anything that contains promethazine (brand names include Phenergan, Promethegan)

Others:
Riboflavin (B2), kidney infection, kidney disease, diabetes, liver disease

METHAMPHETAMINE / AMPHETAMINE

Over-the-Counter:
Cold and allergy meds that contain ephedrine, pseudoephedrine, propylephedrine, phenylephrine, or desoxyepherine (Brand names include Nyquil, Contact, Sudafed, Allerest 12 hour, A.R.M., Triaminic 12, Ornade, Tavist-D, Dimetapp, Sinex, Neosynephrine, Actifed, Bayer Select Maximum Strength Sinus Pain Relief Caplets, Contact Non-Drowsy Formula, Dristan Cold Caplets, Maximum Strength Sudafed Sinus Caplets, Maximum Strength Tylenol Sinus Gelcaps, Sinus Excedrin Extra Strength Caplets, Drixoral Cold and Flu, Robitussin Cold and Flu, Vicks Inhaler and Afrin)
Diet aids containing phenylpropanolamine (Brand names include Dexatrim and Accutrim). Asthma medications such as Marax, Bronkaid tablets, Primatine Tablets

Prescription Meds:
Drugs used as diet aids such as phentermine (Brand names include Adipex-P, Fastin, Ionamin, ObeNix, Obermine, Parmine). Drugs used for the treatment of ADH or ADHD such as dextroamphetamine (Dexedrine), methylphenidate hydrochloride (Ritalin), pemoline (Cylert). Drugs used for Parkinsons Disease such as selegiline (Eldepryl)

Prescription NSAIDs:
Anaprox, Tolectin, ifenoprofen, fluriprofen, oxaprozin, Ansaid, Clinoril, Dolobid, Feldene, Indocin, Lodine, Meclomen, Nalfon, Naprosyn, Orudis, Relafen, Voltaren

Others:
Kidney infection, kidney disease, diabetes, liver disease

COCAINE

Kidney infection, kidney disease, diabetes, liver disease, amoxicillin. tonic water

OPIATES

Prescription Meds:
Prescription pain medications that contain codeine (i.e Tylenol with Codeine, Emprin, Empracet, Fioricet with Codeine, Fiorinal with Codeine), hydrocodone (i.e. Vicodin, Lortab, Lorcet),oxycodone (i.e. Percocet, Percocdan, Endocet, Roxicet), methadone (Dolophine, Methadose)
Antibiotic used for the treatment of Tuberculosis: rifampicin (Rifadin, Rimactane)

Others:
Kidney Infection, Kidney disease, diabetes, liver disease,poppy seeds

BARBITURATES

Prescription Meds:
Fiorinal for tension headaches, Donnatal for the treatment of irritable bowel syndrome and stomach ulcers, and antiepileptic medications containing phenobarbital (i.e. Dilantin)

Prescription NSAIDs:
Anaprox, Tolectin, ifenoprofen, fluriprofen, oxaprozin, Ansaid, Clinoril, Dolobid, Feldene, Indocin, Lodine, Meclomen, Nalfon, Naprosyn, Orudis, Relafen, Voltaren

Others: Kidney infection, kidney disease, diabetes, liver disease

BENZODIAZEPINES

Prescription Meds:
Many prescription sleeping pill and anti-anxiety medications (i.e. Valium, Ativan, Xanax, Restoril, Serax)

Prescription NSAIDs:
Anaprox, Tolectin, ifenoprofen, fluriprofen, oxaprozin, Ansaid, Clinoril, Dolobid, Feldene, Indocin, Lodine, Meclomen, Nalfon, Naprosyn, Orudis, Relafen, Voltaren

Others:
Kidney infection, Kidney Disease, Diabetes, Liver Disease

LSD

Prescription Meds:
Mirgraine medications containing ergotamine (i.e. Ergostat, Cafergot, Wigraine, Imitrex, Sansert)
Artane for Parkinsons Disease
Elavil (amitriptyline) for depression
Bentyl (dicyclomine) for gastrointestinal spasms
Anti-nausea / Antihistamine preparations containing promethazine