Sources of False Positive Results

All point-of-care (POC) test results are considered presumptive until they have been confirmed using liquid chromatography–mass spectrometry (LC-MS/MS). An in-office POC test provides a preliminary assessment of a patient’s medication compliance, but POC testing has generally accepted limitations. For example, POC testing has higher cutoff values than laboratory testing and POC test results apply only to drug classes, not to individual drugs. These limitations can lead to false negative or false positive test results, depending on what substances the patient has consumed. Therefore, it is important to obtain a full medication history that includes prescription, OTC and herbal medications for each collection event.

This chart is not inclusive of all substances with the potential to cause false positive test results. This chart is for general information only and is not intended to be used as medical advice. For specific drug testing result interpretation questions, please contact us.

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DRUG CLASS

DRUGS TARGETED BY THE POC TEST

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES

Amphetamines

Amphetamine

Amantadine, Brompheniramine, Bupropion, Chlorpheniramine, Chlorpromazine, Desipramine, Desoxyephedrine, Ephedrine, Fluoxetine, Isometheptene, Isoxsurpine, Labetalol, Phenmetrazine, Phentermine, Phenylephrine, Phenylpropanolamine, Promethazine, Pseudoephedrine, Ranitidine, Selegiline, Thioridazine, Tranylcypromine, Trazodone, Trimethobenzamide, Trimipramine, Vicks Inhaler

Methamphetamine

Amantadine, Brompheniramine, Bupropion, Chlorpromazine, Desipramine, Desoxyephedrine, Ephedrine, Fluoxetine, Isometheptene, Isoxsuprine, Labetalol, Phentermine, Phenylephrine, Phenylpropanolamine, Promethazine, Pseudoephedrine, Ranitidine, Selegiline, Thioridazine, Trazodone, Trimethobenzamide, Trimipramine, Vicks Inhaler

Antidepressants (Tricyclic)

Amitriptyline, Desipramine, Doxepin, Imipramine, Nortriptyline, other Tricyclics

Carbamazepine, Cyclobenzaprine, Cyproheptadine, Diphenhydromine, Hydroxyzine, Quetiapine

Barbiturates

Amobarbital, Butalbital, Phenobarbital, Secobarbital, other Barbiturates

Ibuprofen, Naproxen

Benzodiazepines

Alprazolam, Nordiazepam, Oxazepam, Temazepam, other Benzodiazepines

Oxaprozin, Sertraline, Hydroxyzine, Diphenhydramine

Opiates and Opioids

Codeine, Hydrocodone, Hydromorphone, Morphine

Dextromethorphan, Diphenhydramine, Fluoroquinolones (Ciprofloxacin, Levofloxacin, and Ofloxacin), Oxycodone (high contentrations), Poppy Seeds and Oil, Rifampin, Quinine

Methadone

Chlorpromazine, Clomipramine, Diphenhydromine, Doxylamine, Ibuprofen, Quetiapine, Thioridazine, Verapamil

Oxycodone, Oxymorphone

Codeine, Hydrocodone, Hydromorphone (high concentrations), Morphine

Illicits

Cocaine

Amoxicillin, Coca Leaf Teas, Tonic Water

MDMA (Ecstasy)

Phenylpropanolamine, Ephedrine, Pseudoephedrine, Ranitidine, Phentermine

PCP (Phencyclidine)

Chlorpromazine, Dextroamphetamine, Dextromethorphan, Diphenhydramine, Doxylamine, Ibuprofen, Imipramine, Ketamine, Lamotrigine, Meperidine, Thioridazine, Tramadol, Venlafaxine

Marijuana

Dronabinol, Efavirenz, Hemp-containing Foods, Ibuprofen, Ketoprofen, Naproxen, NSAIDs, Piroxicam, Prilosec, Promethazine, Proton Pump Inhibitors (Pantoprazole), Protonix, Sulindac, Tolmetin

DRUG CLASS

Amphetamines

DRUGS TARGETED BY THE POC TEST: Amphetamine

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Amantadine, Brompheniramine, Bupropion, Chlorpheniramine, Chlorpromazine, Desipramine, Desoxyephedrine, Ephedrine, Fluoxetine, Isometheptene, Isoxsurpine, Labetalol, Phenmetrazine, Phentermine, Phenylephrine, Phenylpropanolamine, Promethazine, Pseudoephedrine, Ranitidine, Selegiline, Thioridazine, Tranylcypromine, Trazodone, Trimethobenzamide, Trimipramine, Vicks Inhaler

DRUGS TARGETED BY THE POC TEST: Methamphetamine

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Amantadine, Brompheniramine, Bupropion, Chlorpromazine, Desipramine, Desoxyephedrine, Ephedrine, Fluoxetine, Isometheptene, Isoxsuprine, Labetalol, Phentermine, Phenylephrine, Phenylpropanolamine, Promethazine, Pseudoephedrine, Ranitidine, Selegiline, Thioridazine, Trazodone, Trimethobenzamide, Trimipramine, Vicks Inhaler

Antidepressants (Tricyclic)

DRUGS TARGETED BY THE POC TEST: Amitriptyline, Desipramine, Doxepin, Imipramine, Nortriptyline, other Tricyclics

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Carbamazepine, Cyclobenzaprine, Cyproheptadine, Diphenhydromine, Hydroxyzine, Quetiapine

Barbiturates

DRUGS TARGETED BY THE POC TEST: Amobarbital, Butalbital, Phenobarbital, Secobarbital, other Barbiturates

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Ibuprofen, Naproxen

Benzodiazepines

DRUGS TARGETED BY THE POC TEST: Alprazolam, Nordiazepam, Oxazepam, Temazepam, other Benzodiazepines

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Oxaprozin, Sertraline, Hydroxyzine, Diphenhydramine

Opiates and Opioids

DRUGS TARGETED BY THE POC TEST: Codeine, Hydrocodone, Hydromorphone, Morphine

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Dextromethorphan, Diphenhydramine, Fluoroquinolones (Ciprofloxacin, Levofloxacin, and Ofloxacin), Oxycodone (high contentrations), Poppy Seeds and Oil, Rifampin, Quinine

DRUGS TARGETED BY THE POC TEST: Methadone

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Chlorpromazine, Clomipramine, Diphenhydromine, Doxylamine, Ibuprofen, Quetiapine, Thioridazine, Verapamil

DRUGS TARGETED BY THE POC TEST: Oxycodone, Oxymorphone

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Codeine, Hydrocodone, Hydromorphone (high concentrations), Morphine

Illicits

DRUGS TARGETED BY THE POC TEST: Cocaine

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Amoxicillin, Coca Leaf Teas, Tonic Water

DRUGS TARGETED BY THE POC TEST: MDMA (Ecstasy)

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Phenylpropanolamine, Ephedrine, Pseudoephedrine, Ranitidine, Phentermine

DRUGS TARGETED BY THE POC TEST: PCP (Phencyclidine)

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Chlorpromazine, Dextroamphetamine, Dextromethorphan, Diphenhydramine, Doxylamine, Ibuprofen, Imipramine, Ketamine, Lamotrigine, Meperidine, Thioridazine, Tramadol, Venlafaxine

DRUGS TARGETED BY THE POC TEST: Marijuana

SUBSTANCES WITH POTENTIAL TO CAUSE FALSE POSITIVES: Dronabinol, Efavirenz, Hemp-containing Foods, Ibuprofen, Ketoprofen, Naproxen, NSAIDs, Piroxicam, Prilosec, Promethazine, Proton Pump Inhibitors (Pantoprazole), Protonix, Sulindac, Tolmetin

The information provided is for educational purposes only and is not intended to be used as medical or legal advice. Detection times are approximate and may be influenced by a number of factors, including BMI, duration of drug use, dosage and interindividual metabolic differences. For specific drug testing result interpretation questions, please contact us.