Air to muscle and blood/plasma to muscle distribution of volatile organic compounds and drugs: Linear free energy analyses

Distribution coefficients, K-mus, from the gas phase to the muscle have been collected for volatile organic compounds (VOCs). For 114 VOCs, a linear free energy relationship (LFER) yields an equation for log K-mus with R-2 = 0.944 and SD = 0.267; construction of a training and test set shows that the LFER can predict further values to around 0.30 log units. The combination of the log Kmus values with values for air to blood yields distribution coefficients from blood to muscle, log P-mus, for 110 VOCs; the corresponding LFER has R-2 = 0.537 and SD = 0.207 and a predictive capability of 0.22 log units. We also collected data on the distribution of drugs from blood or plasma to muscle and showed that the two sets of data can be combined. A LFER for blood/plasma to muscle for 59 drugs has R-2 = 0.745 and SD = 0.253 and a predictive capability of 0.25 log units. Finally, we show that the in vitro data on VOCs and the in vivo data on drugs can be combined; a LFER on the total data for 163 compounds has R-2 = 0.595, SD = 0.220, and a predictive capability of about 0.25 log units.