Spotting counterfeit antibiotics with a simple test

A simple paper test developed by a chemistry laboratory in Colorado State University can detect false or sub standard antibiotics

The paper-based test can quickly identify a falsified or substandard antibiotic. Image credit: John Eisele

A US-based laboratory in the Department of Chemistry at Colorado State University, is using a simple and inexpensive test, to identify falsified or substandard antibiotics.

The research group has created a paper-based test that can quickly determine whether an antibiotic sample is of the appropriate strength, or diluted with filler substances like baking soda.

Similar to the mechanism of a home pregnancy test, a strip of paper turns a distinctive colour if a falsified antibiotic is present.

“In this country [US], we take for granted that our antibiotics are good – we don’t even think twice,” said Kat Boehle, first author on the paper.

“But counterfeit and substandard antibiotics are an extremely common thing in other parts of the world. The goal of this project has been to make a cheap detection device that is easy to use; our device costs literally a quarter to make,” she said.

Bacteria naturally produce beta-lactamase that can give them resistance to antibiotics by chemically binding to portions of the antibiotic molecule. The researchers used this enzyme to enable them to detect the presence of antibiotics in a given sample.

For the test, the user dissolves the antibiotic in water and adds the solution to a small paper device. The paper contains nitrocefin, which changes colour when it reacts with the enzyme. In this setup, the antibiotic and the nitrocefin on the paper are in competition to bind with the enzyme in a detection zone.

With a good antibiotic dose, there is little colour change in the paper strip, because the antibiotic outcompetes the nitrocefin and successfully binds with the beta-lactamase enzyme. But in a falsified or weakened antibiotic, the paper goes red, because the enzyme instead reacts with the nitrocefin.

The test is effective for a broad spectrum of beta-lactam antibiotics, but there’s room for refinement. The sample most misidentified by untrained users was acetylsalicylic acid – commonly known as aspirin – which did not turn as red as the other false samples because its acidic pH destabilised the reaction. Being able to more accurately distinguish such specific chemicals will be the subject of future optimisation of the new test, the researchers say.

Taking just 15 minutes the simple test can be performed by an untrained professional. Traditional approaches for testing drug purity have historically relied upon large, expensive analytical equipment in labs, including mass spectrometry, making it challenging or impossible for developing countries to access these technologies easily.


  1. Katherine E. Boehle, et. al., "Paper-Based Enzyme Competition Assay for Detecting Falsified β-Lactam Antibiotics". ACS Sensors, 3(7), (2018).