Pharmacokinetics Flashcards
Factors that affect drug absorption
Rate of dissolution Surface area Blood flow Lipid solubility pH partitioning
Four basic pharmacokinetic processes
Absorption
Distribution
Metabolism
Excretion
Weak acids and weak bases can only cross membranes when in their ____ form
Unionized
Non polar drugs do or do not readily cross cell membranes
Do
Polar drugs do or do not readily cross cell membranes
Do not
Drugs are active or inactive when bound to proteins in the blood
Inactive
Primary site of biotransformation
Liver
Reactions of phase I biotransformation
Oxidation, reduction, hydrolysis
Reactions of phase II biotransformation
Conjugation
Products of phase I biotransformation are usually __? Uses the ___ system? These enzymes are located where?
More polar metabolites
Cytochrome P450 system
Smooth ER
Inducers of the cytochrome P450 system
Phenobarbital, carbamazepine
These decrease the bioavailability of other drugs
Inhibitors of the cytochrome P450 system
Erythromycin, ketoconazole, grapefruit juice
These will increase bioavailability of other drugs
Pharmacokinetic math terms:
k_a
S
F
Rate constant for absorption (units/unit time) Salt factor (drugs are often administered as their salt but only parent compound is measured) Bioavailability (fraction of drug that reaches the blood stream)
Excretion rate:
Define
With first order kinetics, this ___ as the plasma concentration increases
Mass eliminated per unit time
Increases
Clearance:
Define
With first order kinetics, this ___ as the plasma concentrations change
Plasma volume from which all of the solute is removed per unit time (flow rate)
Remains constant
