BM1022 Lecture 25: Lecture 25 - Distribution
Document Summary
How does that drug get to the active tissue. Affinity for binding with blood proteins varies between drugs. Build up of drug (or hormone, electrolyte) inside cell due to pka. Drugs with low pka (more basic) become more ionized inside the cell and lower proportion can cross cell membrane. Conversely, drugs with higher pka (more acidic) are more lipophilic (un-ionized) inside cell than out. Example: warfarin remains in blood (pka = 5. 87). Lipid environmental toxins and drugs with high lipid solubility can accumulate in fat due to low blood flow and binding. Bone tetracycline antibiotics high affinity for bone (not suitable prenatal / early childhood). Drug must pass through cell membranes due to tight cell junctions. Transcellular (through membranes) thickness of placental membrane (syncytiotrophoblast) decreases with maturation. Conversely, drugs with higher pka (more acidic) are more lipophilic (un-ionized) inside cell. Lipid environmental toxins and drugs with high lipid solubility can accumulate in fat due to.
