Optical methods for in-vivo pharmacokinetics (Invited Paper)

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Abstract
The kinetics of light absorbing compounds can be followed continuously in vivo by the use of reflection photometry to measure the changes in total optical attenuation of tissue. This method was employed in anesthetized DBA mice with SMT tumors. The pharmacokinetics in the tumor tissue of two closely related pheophorbides were followed continuously for the first two hours following tail vein injection2. The results of these measurements were correlated with the response of the tumors to photodynamic therapy and the plasma clearance. MPM (methyl pheophorbide methyl ether) cleared the tumor tissues with kinetics that matched the plasma clearance (20 min). MPH (methyl pheophorbide hexyl ether) showed steady accumulation and retention while the plasma was clearing the sensitizer. When the tumors were subsequently exposed to light (665 nm) the MPM tumor was not responsive even at short times (10 min) post injection. A response was produced in these two mice only when they were exposed to the treatment light and simultaneously injecting the MPM at high doses. MPH treated mice responded to treatment at 24 hours post injection. Reflection measurements of tissue attenuation at that time indicated that significant quantities2 of MPH were still present.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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