Indirect Evaluation of Lithium Level in Blood Using Non-invasive Sweat Biosensors

Lithium (Li+) is one of the most widely used and studied medications for treating of Bipolar Mood Disorder, resistant cases of Major Psychiatric Disorders and especially Major Depressive Disorder. After administration, more than 95% of administered dose of Li+ is eliminated unchanged in the urine, less than 5% - in the saliva, sweat, and feces. Up to 40% of patients that are on Li+ therapy encounter adverse effects that can be explained by drug involvement in various biochemical processes. Li+ efficacy and side effect manifestation are obviously determined by the drug concentration in blood. The optimal way to prevent manifestation of side effects is to control that Li+ serum level is within therapeutic range. A blood test is often ordered to monitor the serum level of Li+ to ensure target serum levels are reached. The available methods for blood Li+ are invasive, time consuming, and cause of discomfort for patients, yet are of a great importance as levels of drug in blood outside the therapeutic range may dramatically affect patient health. It is especially of importance for Li+ treatments it has a narrow therapeutic window - 0.6-1.5 mmol/L. Thus, there is a growing need for a reliable, comfortable, and inexpensive method for detection of Li+ in blood that can be performed easily in an in-patient setting and automatically whenever necessary without the need for a clinic visit out-patient setting. Spectrophon LTD has developed an algorithm that allows calculation of levels of various compounds contained in sweat using standard PPG sensors with special coating and thus to estimate the levels of corresponding chemicals in the bloodstream. This algorithm has proven useful and accurate in clinical trials on detection of dehydration level, blood sodium level, and blood glucose level. We suggest that Spectrophon biosensors can be used to detect the levels of Li+ in sweat that will allow non-invasive estimation of the level of corresponding medication in blood in real-time.