Sensor system keeps track of anti-epileptic medicine in saliva

This is the claim of researchers in Oregon State University’s College of Engineering, whose US National Institutes of Health-funded study is published in the Journal of Applied Electrochemistry.

Globally, there are an estimated 68 million people living with epilepsy, with around 3.4 million with the condition in the US, including nearly half a million children.

In a statement, Lael Wentland, a postdoctoral researcher at OSU, said: “With further development, our system could be used to empower epilepsy patients by letting them monitor their anti-seizure drug levels from home. From the data our sensor can generate, a personalised drug dosage can be determined, reducing the chances of toxic side effects from too-high doses and seizures from ineffective low doses.”

Epilepsy is a neurological disorder characterised by muscle spasms, convulsions and loss of consciousness in addition to seizures, and its negative impacts to physical and mental health are numerous.

“It’s exciting to be making progress toward a medical tool that people with epilepsy can use to improve their therapy and quality of life,” said Elaine Fu, an associate professor of bioengineering who co-led the research with Wentland.

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Fu, Wentland and fellow Oregon State researchers Stephen Ramsey, Matthew Johnston, Jacob Cook and Jade Minzlaff built and demonstrated a hand-held, microfluidic-based system that can detect a seizure-preventing drug from saliva without the saliva first being subjected to a lengthy pre-treatment process.

Anti-epileptic drugs (AEDs), have been available for over a century but the optimal dose – high enough to control seizures and low enough not to create other problems – varies widely from patient to patient, Wentland said.

“As one example, the often-prescribed drug carbamazepine, or CBZ, interacts strongly with other AEDs and also with antibiotics,” Wentland said. “Also, the way it moves through the body varies a great deal from one person to the next, and above a very narrow therapeutic range it’s toxic to the point of causing poor muscle control, disorientation, hallucinations and even coma.”

The standard way of measuring how much of a drug is in a patient’s system is with a blood test conducted in a laboratory, but the long lag – it can be as much as several days from the time blood is drawn until the results are in – limits the test’s usefulness for people on AEDs, the researchers said.

Aiming to shorten the turnaround time, the researchers looked to saliva.

“Saliva, which is easily and non-invasively accessed, has terrific potential for health monitoring, and it’s already been shown that the concentration of CBZ in saliva correlates with the concentration of the drug in the bloodstream,” Fu said. “But saliva also presents a challenge for the electrochemical detection of the drug because saliva has a complex composition that can result in signal interference.”

Wentland and Fu led the development of a disposable, electrochemical flow cell that enables the detection of therapeutic levels of CBZ from a small amount of saliva.

Ramsey, associate professor of computer science and biomedical sciences, spearheaded the creation of a new signal processing algorithm for the quantification of the electrochemical signal. Johnston, associate professor of electrical and computer engineering, led the development of the system’s miniature potentiostat, an analytical instrument that controls the working electrode’s potential in an electrochemical cell that has multiple electrodes.