Monitoring levels of an epilepsy drug in the body can take seconds and doesn't need blood samples
A method to analyse drug levels in the body could allow people with epilepsy to avoid weeks of blood tests, claim scientists from Switzerland.
Valproic acid is an anticonvulsant drug used in the treatment of epilepsy; however, in the body, the acid binds to proteins and the concentration also can be influenced by over-the-counter medicines. The variations in the concentration mean that the amount of pharmacologically relevant valproic acid needs to be carefully monitored for the first few weeks and the dosage adjusted to compensate. The concentration is normally measured using blood samples from patients, and it can take a long time for the results to come back.
Now, Renato Zenobi at the Swiss Federal Institute of Technology in Zurich and co-workers have developed a method to measure valproic acid metabolite levels in breath using electrospray mass-spectrometry.
The metabolites act as biomarkers that provide a molecular fingerprint of the compounds in breath. The team can use the amounts of metabolites to calculate the amount of valproic acid in the body. Using mass spectrometry to measure drug metabolites in breath allows the direct monitoring of drug levels without the patients giving blood, removing the need for any invasive or painful procedures. The approach has other advantages as Zenobi says the method ’gives a result in seconds’.
Gary Siuzdak, director of the Center for Metabolomics and Mass Spectrometry at The Scripps Research Institute in California, US, welcomes the research. ’This is an intriguing, non-invasive, application of mass spectrometry to pharmaceutical metabolism and holds equally interesting potential for examining endogenous metabolites related to disease,’ he says.
Link to journal article
Real-time, in vivo monitoring and pharmacokinetics of valproic acid via a novel biomarker in exhaled breathGerardo Gamez, Liang Zhu, Andreas Disko, Huanwen Chen, Vladimir Azov, Konstantin Chingin, G?nter Kr?mer and Renato Zenobi,?Chem. Commun., 2011, 47, 4884DOI:10.1039/c1cc10343a