Famprofazone use can be misinterpreted as methamphetamine abuse.

Area of Science:

• Forensic Toxicology
• Pharmacology

Background:

• Famprofazone, a component of Gewolen, is an analgesic.
• Metabolism of famprofazone yields methamphetamine (MA) and amphetamine (AM).
• Positive MA tests in Taiwan can lead to misinterpretation of legitimate famprofazone users as illicit drug abusers.

Purpose of the Study:

• To determine if a single dose of famprofazone can result in urine MA concentrations exceeding Taiwan's controlled substance regulations.
• To investigate the potential for misidentification of legitimate famprofazone users as methamphetamine abusers.

Main Methods:

• Six subjects received a single 25 mg dose of famprofazone.
• Urine specimens were collected over 48 hours post-administration.
• Screening by immunoassay followed by confirmation with gas chromatography-mass spectrometry (GC-MS).

Main Results:

• Urine MA and AM concentrations ranged from 901-2670 ng/mL and 208-711 ng/mL, respectively.
• 18.8% of samples exceeded 500 ng/mL for amphetamines via immunoassay.
• Positive MA (>or= 500 ng/mL) and AM (>or= 100 ng/mL) results were observed within 2-34 hours, meeting Taiwan's legal thresholds.

Conclusions:

• Legitimate famprofazone use can produce urine MA and AM levels that trigger positive results under current Taiwanese regulations.
• There is a significant risk of misclassifying individuals using famprofazone as illicit methamphetamine abusers.
• Current drug testing regulations may require re-evaluation to distinguish therapeutic famprofazone use from illicit MA abuse.