Famprofazone Use Can Be Misinterpreted as Methamphetamine Abuse

Abstract

Famprofazone, a major ingredient of Gewolen, is an analgesic that has been demonstrated to be metabolized to methamphetamine (MA) and amphetamine (AM) following administration. Therefore, a famprofazone user may be interpreted as an illicit MA abuser in Taiwan because the user's urine tested positive for MA. The purpose of this study was to investigate whether the concentration of MA metabolized from a single dose of Gewolen users would offend the official controlled substance regulation and be identified as MA-positive. Subjects (n = 6) received 25 mg of famprofazone and collected all urine specimens at certain timed intervals for 48 h after drug administration. The urine specimens were screened by immunoassay and then confirmed by gas chromatography-mass spectrometry (GC-MS). The highest concentration of amphetamines by immunoassay was 1954 ng/mL, and 18.8% of the urine specimens' amphetamines concentrations exceeded 500 ng/mL. The MA and AM concentrations by GC-MS analysis of these urine specimens ranged from 901 to 2670 ng/mL and 208 to 711 ng/mL, respectively. These urine specimens were interpreted as MA-positive (>or= 500 ng/mL MA and >or= 100 ng/mL AM), according to the official test methods of Taiwan. The MA positive results appeared within 2-34 h. It is therefore clearly possible to misinterpret the legitimate famprofazone user as an MA abuser in Taiwan.

Executive Summary: American Association of Clinical Chemistry Laboratory Medicine Practice Guideline—Using Clinical Laboratory Tests to Monitor Drug Therapy in Pain Management Patients

“…There are a few articles that describe the use of quantitative testing and clinical algorithms, but none demonstrate how their use improved outcomes. Therefore, there is no evidence that the reporting of quantitative drug concentrations is more effective in facilitating the assessment of any outcomes for pain management patients (25,50,56,59,(62)(63)(64).…”

True‐Positive Drugs of Abuse Test Results Due to Use of Prescriptions and Nonprescription Drugs

“…The tea bags usually contain approximately 1 g of plant material, usually dried raw coca leaves that are also a natural source of cocaine. Urinary samples were collected at 2,5,8,15,21,24,43, and 68 hours after drinking the tea. When the tea was prepared, 1 cup of Peruvian coca tea had an average of 4.14 mg of cocaine, whereas 1 cup of Bolivian tea had an average of 4.29 mg of cocaine.…”

“…The positive methamphetamine results appeared within 2 -34 hours postingestion (8) . Further analysis of these specimens using GC/MS indicated that methamphetamine concentrations ranged from 901 to 2670 ng/ mL and amphetamine concentrations ranged from 201 to 711 ng/mL, respectively.…”

Human and rat microsomal metabolites of N-tert-butoxycarbonylmethamphetamine and its urinary metabolites in rat

“…Metabolism of termed "precursor drug" to MA has been described for several compounds including benzphetamine, famprofazone and selegiline [2,[9][10][11][12][13]. Previous studies have investigated their metabolism and excretion, clarifying that specific metabolites, proportion of MA to amphetamine, and enantiomers of MA are useful indicators for interpreting the origin of MA in urine samples.…”