Week 2- II Pharmacokinetics Flashcards
What is the blood-brain barrier? Name two ways drugfs enter the brain.
The capillaries of the brain do not have gaps between the cells of the capillaries. Drugs must pass through the cell membrane or be transported by a transport system.
The cytochrome P450 system refers to a family of enzymes which does what?
Metabolize drugs.
Kidneys are unable to excrete what type of drugs?
Highly lipid-soluble.
Define prodrug.
An inactive compound which can be converted into an active drug.
Define the first-pass effect.
Blood passes through the liver before reaching the systemic circulation.
How does cigarette smoking affect the rate of drug metabolism?
Increases.
If a drug binds to albumin and displaces another drug from the site, what happens to the serum concentration of the drug displaced?
Increases.
At what age does the infant’s liver develop into its full capacity?
One year.
The most important organ for drug excretion is what?
The kidneys.
Which drugs remain in the urine for excretion?
Polar and ionized drugs.
Define enterohepatic circulation.
Drugs excreted in the bile are reabsorbed into the portal blood.
What type of drugs easily enters breast milk?
Lipid-soluble or lipophilic
Define the minimum effective concentration (MEC).
The plasma drug level at which a drug has a therapeutic effect.
Define toxic concentration.
The plasma drug level at which toxic effects begin.
Define therapeutic range.
The range of plasma drug levels that fall between the MEC and the toxic concentration.
Define duration.
The length of time the drug is in the therapeutic range.
Define half-life.
The time required for the amount of drug in the body to decrease by 50%. For example if the half-life is one day, in 1 day, 50% is left; in 2 days, 25% is left; in 3 days, 12.5% is left; etc.
How many half-lives does it take to clear a drug from the body?
4 half-lives
Define plateau. What is the relationship between absorption and elimination?
Steady concentration of drug reached after repeated doses.
Absorption = Elimination
Why are loading doses given?
To shorten the time to plateau.
Why are maintenance doses given?
To continue the plateau.
What type of drugs cross the placenta?
Lipid-soluble or lipophilic.
