Indirect relationship between lipophilicity and maximum residue limit of drugs determined for fatty tissue

The aim of this study was to determine the correlation between lipophilicity and maximum residue limit (MRL) value specified for veterinary drugs in the fatty tissue of various animal species. The analysis was performed on a group of 73 compounds with different modes of action and MRL values determined for the fatty tissue of animals. Additionally, the logarithm of water/organic phase partition ratio (LogP) and the ratio of ionised and unionised substance in buffer with pH 7.4 (LogD_7.4) were calculated. The main analysis was performed after the division of the whole group into six fractions. The linear correlation and regression analysis were used to determine the indirect relationship between the mean arithmetic value of LogP or LogD_7.4 in selected fractions and related LogMRL of the drugs tested. The calculations revealed a linear correlation between fractioned lipophilicity and LogMRL values for the analysed compounds. The existence of indirect relationship between lipophilicity and MRL values determined for fatty tissue was confirmed.