Flashcards in 3 Medical Mathematic: Distribution of Drugs Deck (9)
What is distribution of drugs?
Is the transport of drugs from the plasma to the tissues (site of action, site of storage, site of biotransformation)
What factors affect the distribution of drugs?
Physicochemical properties of the drug (Lipid solubility, degree of ionization)
Plasma protein binding
Affinity of drugs to certain tissues
Describe plasma binding proteins
Acidic drugs bind mainly to albumin.
Basic drugs bind mainly to acid alpha 1-glycoproteins and lipoproteins.
Some drugs bind to globulin (e.g., steroids).
Prolongs the half-life of the drug.
The bound form is inactive, can not be distributed, metabolized or excreted by glomerular filtration.
The rate of binding depends mainly on the amount of the drug.
Binding can be modified by disease.
Drugs can compete on the binding sites.
Plasma protein binding depends on the species.
Describe blood flow as it affects the distribution of drugs
The rate of tissue perfusion relative to the tissue mass
– Highly perfused tissues
Brain, liver, kidney, endocrine glands
– Moderately perfused tissues
– Poorly perfused tissues
Bone, adipose tissue
• Alteration of blood flow
– Physiological factors
List the tissue barriers
The blood-brain barrier
Describe The blood-brain barrier
Tight capillary endothelial junctions
The presence of glial cells
Flow of the CSF into venous drainage
Active transport mechanisms for extrusion of organic acids or bases
What factors influence the blood-brain barrier?
High doses of organic solvents (alcohol)
High doses of heavy metals (lead, mercury)
Examples of the Affinity of drugs to certain tissues
Tetracycline to calcium in skeletal tissues
Aminoglycosides to kidney tissue
Trapping of iodine by the thyroid gland