Spatial and Temporal Tracking of Counterfeit Phosphodiesterase Type V Inhibitors Use Based on Wastewater Analysis

Area of Science:

• Environmental Chemistry
• Forensic Toxicology
• Public Health

Background:

• Phosphodiesterase type V inhibitors (PDE-5is) are crucial for erectile dysfunction treatment, but counterfeit versions pose significant public health risks.
• Global demand for PDE-5is is increasing, driving the circulation of illicit pharmaceuticals.

Purpose of the Study:

• To assess temporal and spatial trends of counterfeit PDE-5i use in Dalian, China, using wastewater analysis.
• To quantify community-level consumption of sildenafil and its metabolite, desmethylsildenafil.
• To compare wastewater-derived consumption data with official prescription sales.

Main Methods:

• Solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze 116 influent wastewater samples.
• Samples were collected from Dalian, China, between 2017 and 2022.
• Wastewater treatment plant catchment areas were used for spatial analysis, categorizing populations by urban, rural, college student, and island resident demographics.

Main Results:

• Sildenafil was detected in 94.5% of samples, with concentrations up to 75.4 ng/L, and its metabolite desmethylsildenafil up to 107 ng/L.
• Estimated sildenafil consumption increased from 40.8 to 87.8 mg/d/1000 inh between 2017 and 2022, significantly exceeding prescription data (approx. 20% of total use).
• Urban areas showed higher consumption (70.4 mg/d/1000 inh) than rural areas (25.4 mg/d/1000 inh), with college students and island residents exhibiting lower usage.

Conclusions:

• Wastewater-based drug surveillance effectively tracks community-level consumption of nonprescribed and counterfeit pharmaceuticals.
• The majority of sildenafil use in Dalian is through illicit channels, with estimated annual counterfeit use exceeding 100 kg.
• Findings provide crucial data for regulatory bodies to address the public health risks associated with counterfeit PDE-5is.