Flashcards in Distribution Deck (13)
Name 3 locations where drugs may distribute through the bloodstream?
site of action, site of storage and site of elimination
in relation to absorption when does distribution begin?
before absorption is finished
what is one thing to consider when dealing with knowing the quanty that enters the body and the actual result?
Most drugs distribute throughout the body, and goes where it is not needed. Thus only a small fraction reaches the receptor sites.
what is the tissue order in which the drug distributes through the body (ie where does it act first)
1. plasma, 2. extracellular tissue fluids, 3. cells. Only a small fraction of each dose reaches the target receptor sites.
what are the 3 factors that affect the drug distribution in the body?
1. physicochemical properties
2. Anatomy and physiology of patient
3.plasma protein binding.
give an example of physicochemical properties, that effect the drug distribution
lipid solubility, degree or ionization or size and molecular weight of the drug
what are two examples of anatomy and physiology of patients that may effect drug distribution.
1. tissue perfusion (where organs with higher blood flow get more drugs, less-well-purfused tissues absorb the majority of the drug.)
2. BBB (blood brain barrier)- its impermeable to plasma proteins, and water soluble substances will only enter slowly
give an example of a plasma protein that effects the distribution of drugs.
its the major carrier of weak acids. protein-bound fraction of drug cannot enter tissues, cannot be eliminated via kidneys, an inert pool of circulating drug.
what is volume of distribution and how is it calculated?
its a method to estimate how widely a drug distributes throughout the body. its useful for calculating loading dose of a drug needed to achiece a specific plasma drug level. Its calculated by dividing the amount of drug in the body, by the plasma drug concentration
what is the relationship of body volume to body weight?
BV is 1 L/kg of BW
what happens when the Vd is >1 L/Kg of BW?
this indicates that the preferential distribution is to the tissues other than blood.
what are some distribution properties of water-soluble drugs?
1. tend to have small to intermediate Vd values
2. Distributes well in blood plasma
3. distributes well in the interstitial fluid
4. does not enter intracellular fluids