In some cases, it's possible to get a positive test result even if you do not take amphetamines. This is called a false positive. Test results have come back positive because patients used a Vicks inhaler or have taken certain antihistamines or cold medications. You may also get a false positive if you use the drug bupropion for depression or to help you quit smoking. Talk with your health care provider about whether the prescription and over-the-counter drugs you take could cause a false positive test result