[Volume of distribution of drugs: an apparent data in pharmacology].

Once the drug has been given and reaches the vascular system of the patient, some drugs are distributed only to the body fluids (plasma plus extracellular water), while others are bound extensively in body tissues. Therefore, the volume of distribution of a drug is not a real volume. Indeed, it is an apparent volume giving a mathematical measure and an approach of the extent of tissue distribution of the drug into the body. Age, pregnancy, renal insufficiency and drug interactions among others, are pathophysiological factors that may alter the fraction of circulating drug bound to albumin and hence, its body distribution that may affect therapeutic response.