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→Distribution
The '''Volume of Distribution (V<sub>d</sub>)''' is a measure of the volume of fluid needed tocontain the total amount of drug at its plasma concentration.
The '''Volume of Distribution (V<sub>d</sub>)''' is a measure of the volume of fluid needed to contain the total amount of drug at its plasma concentration.
V<sub>d</sub> depends upon the ability of a drug to enter plamsa and interstitial fluid and to cross cell membranes and gives a good indication of the extent of drug distribution.
V<sub>d</sub> depends upon the ability of a drug to enter plamsa and interstitial fluid and to cross cell membranes and gives a good indication of the extent of drug distribution.
* Very High (>1l/kg) - concentrated in a body fluid other than plasma and there may be bound residues eg i fat
* Very High (>1l/kg) - concentrated in a body fluid other than plasma and there may be bound residues eg i fat
Lipid-soluble drugs reach all compartments and can accumulate in fat. Whilst lipi-insoluble drugs are mainly contained in plasma and interstitial fluids; they are usually incapable of crossing the blood-brain barrier.
Lipid-soluble drugs reach all compartments and can accumulate in fat. Whilst lipi-insoluble drugs are mainly contained in plasma and interstitial fluids; they are usually incapable of crossing the blood-brain barrier.
==Metabolism==
==Metabolism==