A for Absorption !
Absorption is the movement of drug from its site of administration into the circulation. Not only the fraction of the administered dose that gets absorbed, but also the rate of absorption is important. Routes of drug administration and absorption of drugs (sr: Rang and Dale's Pharmacology) Except when given intravenous, the drug has to cross biological membranes. Other factors influencing absorption are: Aqueous solubility : Drugs given in the solid form must dissolve in aqueous biophase before they are absorbed. A drug given as watery solution is absorbed faster. Concentration : Passive diffusion depends on concentration gradient : concentrated drug solution is absorbed faster. Area of absorbing surface : Larger it is, faster the absorption. Vascularity of the absorbing surface : Blood circulation removes drug from site of absorption and maintains concentration gradient. Route of administration : Main routes include oral, sublingual, rectal, topical application, inhalat...
