In vivo measurement of lithium in humans by nuclear magnetic resonance spectroscopy.

In vivo lithium-7 NMR spectroscopy was used to measure muscle and brain lithium levels following the administration of both single and multiple doses of lithium carbonate to normal volunteers. This is the first report of the noninvasive measurement of tissue lithium levels in humans. The results suggest that the relatively slow accumulation of lithium in the brain may be responsible for the delay in therapeutic response that is frequently observed after the initiation of therapy. Further application of this technique should provide a wealth of information on the pharmacokinetics and tissue distribution of lithium in humans.