Amphetamine can be detected in urine for two to three days after ingestion. The half-life of amphetamine is between seven and 32 hours, depending on urinary pH. The half-life increases with higher urinary pH due to free amphetamine reabsorption by the kidney tubules. Lower pH decreases the half-life. The half-life can also increase with repeated use and accumulation of the drug.
Interpretation of positive amphetamine results can be quite challenging due to its similarity in structure to many over-the-counter drugs, as well as prescription drugs. Diet formulations and decongestants such as ephedrine, pseudoephedrine, phentermine, and phenylpropanolamine are examples. For this reason, a positive amphetamine screen should be confirmed to exclude the possibility of a false positive. As with any drug, a confirmed result is considered a true finding. Because of the specificity of mass spectroscopy, false-positive confirmations should never occur.
Amphetamine is prescribed legitimately as Adderall.
