Watkins has developed and patented a breath test to predict how well patients will metabolize certain drugs. The liver is the main organ that processes drugs, and because liver function is often measured using a breath test, he said, it seemed logical to measure drug metabolism the same way. In a recent study, Watkins' erythromycin breath test accurately predicted how well 22 patients would metabolize the chemotherapy drug docetaxel. Other patients who process a chemotherapy treatment faster than expected may not get a dose that's strong enough to fight their cancer. Watkins' test measures the amount of carbon dioxide emitted in a patient's breath after taking a trace dose of the antibiotic erythromycin.
Carbon dioxide is the main byproduct produced when the liver processes erythromycin.
A high level of carbon dioxide would mean that the patient was metabolizing the drug quickly, while a low score would show that the liver was eliminating the drug more slowly. After the breath test, researchers gave patients the normal doses of docetaxel and used blood tests to measure its levels in their bodies. The researchers didn't know the results of the breath tests until after the study was over. The breath-test results matched those from the blood tests. And they jibed with the patients' response to the chemotherapy.