According to the search results, some medications can cause a false positive for methamphetamines in drug tests. These medications include:

• Amantadine, a drug that can prevent the flu and treat symptoms of Parkinsons disease
• Aripiprazole, an antipsychotic drug
• Dextromethorphan (Robitussin, Delsym)
• Diphenhydramine (Benadryl)
• Certain decongestants
• Metformin (Glucophage), a medication used to treat type 2 diabetes
• Promethazine, a medication used to relieve nausea and vomiting
• Labetalol (Trandate), a medication used to treat high blood pressure
• Bupropion, a medication used to treat depression and to help people quit smoking
• Trazodone, a medication used to treat depression and anxiety
• Chlorpromazine, a medication used to treat schizophrenia and other mental health disorders

It is important to note that false-positive results can be due to a laboratory error, but the most common reason for a false-positive methamphetamine test is other medications or substances that have a similar structure to methamphetamine. Immunoassay testing for methamphetamine uses antibodies to look for certain drug metabolites, and is the most common test used for initial screening. However, these antibodies may detect drug metabolites with similar structure and characteristics to methamphetamine, leading to false-positive results. Therefore, immunoassay testing should only be considered preliminary and should be followed up by confirmatory testing whenever a test comes back positive.