principles Flashcards
What three types of biochemical reactions are involved in phase I metabolism of drugs?
Reduction, oxidation, and hydrolysis
CYTP450 mediated
What is the formula that describes the therapeutic index (TI) of a drug?
TD50/ED50
In pharmacodynamics, the addition of a noncompetitive agonist ____ (increases/decreases/does not change) the efficacy of the agonist.
decreases
What are three drugs that exhibit zero-order elimination?
Phenytoin and ethanol—aspirin at toxic concentrations (a pea is round like the 0 in zero order)
define potency
Amount of drug needed for a given effect
define efficacy
maximum effect of a drug
Drug A has a therapeutic index of 5 μg/ml, whereas Drug B has a therapeutic index of 30 μg/ml. Which drug would be safer for your patient?
Drug B
In first-order elimination of drugs from the body, what is the relationship between the rate of elimination and the drug concentration?
Rate of elimination is directly proportional to the drug concentration—a constant fraction (rather than a constant amount) is eliminated
What reactions occur in phase II metabolism
glucorindation
acetylation
sulfonation
elderly has “gas”
How does the potency of a partial agonist relate to the potency of a full agonist of the same receptor?
A partial agonist may be more potent than, less potent than, or equally as potent as a full agonist
A 20-year-old man has been taking amphetamines. What substance should you give to enhance the renal clearance of this weakly basic drug?
ammonium chloride
The lowest effective dose of drug X is 200 mg/dL. If given at 600 mg/dL, drug X is lethal. What is the therapeutic window of drug X?
400
600-200 = 400
Phase I metabolism of drugs yields ____ (nonpolar/slightly polar/very polar) molecules that are ____ (inactive/often still active).
Slightly polar; often still active
Phase II metabolism of drugs yields ____ (nonpolar/slightly polar/very polar) molecules that are ____ (inactive/often still active).
very polar, inactive
A patient is on norepinephrine, but the physician also gives phenoxybenzamine. What type of antagonist is phenoxybenzamine on α-receptors?
noncompetitive antagonist
Describe how affinity and vmax increase on a graph
Vmax inc as you go down
affinity inc as you go left (Km dec)
“Cali is greater than here”
Do: competitive or noncompetitive inhibitors cross eachother on a graph?
competitors cross eachother! aka they have the same vmax but different Kms
What type of agonist or antagonist is overcome by the addition of more substrate
reversible competitive inhibitors
Reversible Competitive inhibitors affect efficacy or potency?
decrease potency
What is the formula for Vd
amount of drug in body/ plasma concentration
what is the formula for clerance
Vd x Ke
What is the formula for T 1/2
0.7 x Vd/ CL
What is the formula for loading dose
target plasma concentration x Vd/ bioavailability
what is the formula for maintenance dose
target plasma concentration x CL x dose interval / bioavailability
Half life is a property of ____
first order drugs
how many half lives does it take to reach steady state
4-5
name an example of a competitive antagonist pair
Benzos with flumazenil
name an example of a partial agonist pair
morphine is full with buprenorphine - partial
How is a partial agonist different from a full agonist
lower efficacy
