The bioavailability of a drug is the rate at which the drug becomes available to the body and the extent to which the dose is ultimately absorbed after administration. The extent of bioavailability directly influences plasma concentrations, as well as the therapeutic and toxic effects resulting from oral drug administration. Drugs with poor bioavailability are inefficient because a major portion of a dose never reaches the plasma to exert a pharmacological effect. Low bioavailability is also associated with large inter- subject variability in plasma concentrations and effects. Incomplete oral bioavailability has various causes. These include poor dissolution or low aqueous solubility, degradation of the drug in gastric or intes- tinal fluids, poor intestinal membrane permeation, and presystemic intestinal or hepatic metabolism (Turner et al., 2003). Bioavailability values for drugs can be predicted by:
Bioavailability (%) = -45.20 + 5.08 (electron affinity) + 4.09 (aromatic ring count) -15.83
(HOMO) -3.34 (log F) -0.09 (molar volume) -0.72 (volumetric HLB ) -
Predicted bioavailability of the drugs in the test set was used to evaluate the best overall predictive opti- mum performance model. The linear correlation between predicted and observed values is an indication of the quality of the model predictions.
Reference
Turner JV, Glass BD, Kustrin SA (2003). Prediction of drug bioavailability based on molecular structure. Anal Chim Acta.
485: 89-102.
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