100 likes | 287 Views
Bioavailability Distribution Absorption and Transport. Volume of Distribution. The volume of distribution is given by the following equation: Therefore the dose required to give a certain plasma concentration can be determined if the V D for that drug is known.
E N D
Bioavailability Distribution Absorption and Transport
Volume of Distribution The volume of distribution is given by the following equation: Therefore the dose required to give a certain plasma concentration can be determined if the VD for that drug is known. The VD is not a physiologic value; it is more a reflection of how a drug will distribute throughout the body depending on several physicochemical properties, e.g. solubility, charge, size, etc. VD is often calculated per weight of body – it is not volume any more!
VD Proportion of Drug in body water 0.1 40% 0.15 27% 1 4% 10 0.4%
Two compartment model Blood Tissue
Mode of entry of drugs/toxins Skin transport Respiratory route Oral route
Organ pH Surface Area Time Stomach 1-3 up to 5 m2 0.5-20 h Small Intestine 5-7 200 m2 2 h Colon 7-8 up to 5 2 h – 1 week logC Time
Drug Bioavailability VD (L/kg weight) Diazepam 100 0.5-2 Morphine 15-60 3-5 Pentobarbital 95 0.7-10 Tetrahydrocannabinol 6 9-11 VD Proportion of Drug in body water 0.1 40% 0.15 27% 1 4% 10 0.4%
Surface Area Solubility Concentration in bulk Diffusion Coefficient Diffusion Layer thickness Solid
Aqeous area BiLayer Membrane Hydrophobic area Aqeous area Passive Transport pH1 pH2