Passive diffusion of drugs pdf

Some tissues have spaces between their cells through which drug molecules can pass relatively. Rate of drug diffusion using the fick model of passive. Birger brodin, bente steffansen and carsten uhd nielsen. Pdf on jan 1, 2010, birger brodin and others published passive diffusion of drug substances.

Passive diffusion an overview sciencedirect topics. Lipidsoluble drugs dissolve in the membrane, and are driven through by a concentration gradient across the membrane. Passive diffusion definition of passive diffusion by. Diffusion rate is directly proportional to the gradient but also depends on the molecules lipid solubility, size, degree of ionization, and the area of absorptive surface. These changes increase the passive diffusion of drugs and nutrients to the growing fetus. Factors affecting drug absorption and distribution anaesthesia and. The cell membrane some tissues have spaces between their cells through which drug molecules can pass relatively freely. The diffusion constant, k, incorporates various physicochemical drug properties. Describe the factors which determine the timecourse of systemic accumulation of a drug administered by infusion or multiple doses. Carriermediated facilitated transport occurs for some drugs, particularly those which are analogs of endogenous compounds for. Influence of aqueous diffusion layer on passive drug.

Start studying pr drug absorption passive diffusion. The tendency of a drug to ionize can be characterized by its p k. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Passive diffusion of drugs across membranes request pdf. The concepts of flux and permeability chapter pdf available january 2010 with 1,496 reads how we measure reads.

Infective processes affecting the placenta may result in an increase in the thickness of placental membranes which will reduce passive diffusion across them. Masson faculty of pharmacy, university of iceland, hofsvallagata 53, is107 reykjavik, iceland abstract most drugs permeate biological membranes via passive diffusion and it is. Sometimes various globular proteins embedded in the matrix function as receptors and help transport. Passive diffusion of electrolytesalthough the partition coefficient is an important parameter that governs passive diffusion of a wide variety of endogenous compounds, drugs, and xenobiotics, most of these chemicals are electrolytes with a tendency to ionize in solution electrolytes are either acids or. Rate of drug diffusion using the fick model of passive diffusion. Passage through lipid cell membrane by dissolution in membrane. In most cases, drugs cross cell membranes by passive dif fusion down a concentration gradient due to. Different drugs exhibit differences in their ability to ionize. Passive lipid diffusion is probably the most important absorptive mechanism. Drug absorption merck manuals professional edition. Drug absorption clinical pharmacology merck manuals. Influence of aqueous diffusion layer on passive drug diffusion from aqueous cyclodextrin solutions through biological membranes t. Drug cryptomarkets may provide a mechanism not only for the diffusion drugs across locales, but one that allows researchers and policy makers to monitor the availability of specific drugs by.