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631 Physiological Drug Distribution and Protein Binding
Terms in this set (23)
What is the breakdown of fluids in the body?
Total Body Water = 41 L
Intracellular = 23 L
Extracellular = 18 L
Plasma = 3 L
Interstitial = 15 L
What is true of Hydrophilic Drugs?
Able to distribute within the extracellular fluid, unless they are too big
What is true of Lipophilic Drugs?
Able to distribute throughout the body = entire extra- and intracellular space
What is Perfusion Limited by?
What is Diffusion Limited by?
By the slow progression of drug across the membrane in the tissues
What is true of Perfusion Limited Distribution?
Tissue membrane = no barrier
Highly lipophilic drugs or drugs diffusing across loosely knot membranes such as muscle
Depends on how much blood gets pumped through specific organs
What is true of Permeability Limited Distribution?
Drug enters tissue very slowly
Blood flow = not important
Uptake is determined by Fick's Law
What is true of Free Drug?
Able to interact with the receptors so it is of interest
Bound drug cannot be measured whether that is to plasma proteins or tissue components
T / F: Lipophilic drugs tend to distribute well in body tissue.
T / F: Ionized drugs at physiological pH do not readily distribute into tissues when compared to drugs which are primarily unionized.
T / F: Drugs are generally less distributed to highly perfused tissues.
What drug properties result in them being more likely to cross most membrane barriers?
Unionized and lipophilic
What describes the Apparent Vd?
It relates the plasma drug concentration to the amount of drug present in the body
What is true of half-life with respect to Cl and Vd?
It is prolonged if the 1st is constant and 2nd is increased
What is true of Decreased Protein Binding that results in an Increased Free Drug?
It'll allow more drug to cross cell membranes and distribute into all tissues
More drug will therefore be available to interact at a receptor site to produce a more intense pharmacologic effect
Increased rate of metabolism and decreased half-life = lower total steady state concentration
What is the Pharmacodynamic Response influenced by?
Both the distribution of the drug and the concentration of the unbound drug fraction
What is true of Drug Dose and Dosage Form?
Must be chosen to provide sufficiently high unbound drug concentrations so that an adequate amount of drug reaches the site of drug action
What does the Onset of Drug Action depend on?
The rate of the free drug that reaches the receptor and provides a MEC to produce a pharmacodynamic response
When is Displacement Important?
More than 95% bound and has a narrow therapeutic index
It causes a disproportionate increase in the free drug concentration, which may cause drug intoxication
What is true of Clearance for a Low Extraction Drug?
It depends on plasma protein binding and intrinsic THIS
What is true of Clearance for a High Extraction Drug?
It equals blood flow (Qh)
What does Oral Bioavailability depend on?
Q = liver blood flow
fu = fraction of unbound drug
Clint = intrinsic clearance
What is true of F in Low Extraction drugs?
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