Bioavailability of veterinary drugs in vivo and in silico

The physical and chemical properties of a drug determine the behaviour of its molecule in a living organism. In this paper, the relationship between selected physical and chemical parameters and drug bioavailability in vivo was investigated. Data sets from 75 compounds, which can be administered per os to 11 various animal species were analyzed. The selected parameters for the prediction of the in vivo bioavailability were the lipophilicity (LogP) and the polar surface area (PSA) or apolar surface area (aPSA) of a molecule. It was shown that the calculation of the hybrid parameters aPSA/PSA and LogP + (aPSA/PSA) allows to estimate the oral bioavailability of a drug and its allocation to clusters with either an oral bioavailability of < 70% or > 70%. The performed analysis also showed that an extreme low value of the PSA of a molecule (< 40 square angstroms) combined with the extreme high value of LogP (> 4) is associated with a lower oral bioavailability (< 50%). The results obtained indicate the existence of a relationship between the mean LogP value and aPSA/PSA in silico, and the bioavailability of veterinary drugs as determined in vivo.