Noninvasive, in-situ measurement of drug concentrations in tissue using optical spectroscopy.

A small, lightweight system capable of noninvasive measurement of drug concentrations in tissue, without the use of reagents, would be advantageous for the study of the drug pharmacokinetics in space-travel applications. We have applied elastic-scattering spectroscopy (ESS) for noninvasive, real-time in vivo measurement of the concentrations of certain drugs in tissue, utilizing a simple fiber-optic-probe spectroscopic system. The system uses a broadband light source, enabling the detection of compounds with absorption bands in most regions of the visible, and potentially in the near-infrared (NIR) to 1700 nm. Subcutaneous tumors were grown in 4 Nude mice; the mice were treated with one of two chemotherapy agents, and the ESS system was used to perform pharmacokinetic measurements on the tumors following drug administration. Time histories of the drug concentrations in the tumors agreed with the known pharmacokinetics of the two drugs, and HPLC assays following sacrifice showed good relative correlation with the ESS values. Most photodynamic therapy agents and many chemotherapy drugs, including some that are not fluorescent, are ideal candidates for the ESS system. Importantly, the method can provide absolute measurements of compound concentrations.