distribution of drug after systemic absorption
after systemic absorption highly perfused tissures receive a large amount of total dose. As plasma concentration decreases below the highly perfused tissue, drug leaves the tissues to be redistributed to less perfused tissue. Uptake of drug by tissues is mainly determined by blood flow and if drug can penetrate membrane rapidly. With continuing elimination of a drug the plasma concentration decreases below that in tissue and drug leaves tissues and re-enters circulation. a tissue that accumulates drug acts as a reservoir to maintain the plasma concentration and prolong duration of action.