Pharmacokinetics and pharmacodynamics questions Flashcards
In zero-order kinetics, the rate of elimination of a drug is proportional to the drug concentration
False.
A constant amount of drug is eliminated per unit
time.
A non-competitive antagonist binds irreversibly to the receptor
True.
A competitive antagonist shifts the dose response curve to the left
False. The presence of a competitive antagonist (inhibitor) would shift the dose response curve to the right, with no change in the efficacy (plateau). The rightward shift is caused by competition for the same number of receptors.
The higher the affinity of a drug for its receptor, the higher its potency
False. Potency is inversely proportional to affinity.
Bioavailability (F) refers to the fraction of the dose of a drug absorbed into the systemic circulation
True
Drugs with a high apparent volume of distribution (> 500ℓ) are confined to the plasma
False. Drugs which are lipid insoluble, such as neuromuscular blockers, remain in the blood, and have a low Vd.
A greater proportion of an acidic drug is in its unionized form in an acidic medium
True
Topically administered drugs undergo first-pass metabolism in the liver
False. 1st pass metabolism - Refers to the
elimination that occurs when a drug is first absorbed from the intestine & passes through the liver via the portal circulation
In first order kinetics, the rate of elimination is proportional to the plasma drug concentration
True
The time to steady state depends on the half-life of a drug
True
Drug clearance is dependent on the route of administration
False. Clearance of a drug is independent of
the dose and route of administration
A non-competitive antagonist shifts the dose response curve of the agonist to the left
False. Shifts to the right
The maximal efficacy of a drug is reduced by competitive antagonists
False. The maximal efficacy of a drug is reduced by non-competitive antagonists
Intravenously administered drugs have a higher first pass metabolism than orally administered drugs
False. IV drugs aren’t affected by first pass metabolism
Active transport is a saturable process
True.
Drugs with a high volume of distribution are confined to the plasma
False
The non-ionized form of a drug diffuses across cell membranes to a greater extent than the ionized form.
True
ED50 is the dose at which half the drug is eliminated
False. The ED50 (median effective dose) is the dose of a medication that produces a specific effect in 50% of the population that takes that dose
A partial agonist at a receptor has more intrinsic activity than a full agonist at the same receptor
False. Partial agonist has affinity and less intrinsic activity
a competitive antagonist binds reversibly to a receptor
True
A non-competitive antagonist increases the maximal effect (Emax) of a drug
False. The maximal efficacy of a drug is reduced by non-competitive antagonists
The lower the dissociation constant (Kd), the more potent the drug
True
Intravenous drugs have bioavailability of 50%
False. 100% Bioavailability
Topical administration is a type of parenteral administration
False. Parenteral includes: IV, SC and IM
Sodium bicarbonate increases the pH of the stomach
True
Drugs with an extensive first pass effect require high I.V. doses as compared with oral doses.
False. First pass metabolism affects oral drugs. So oral drugs with high first pass effect would require higher dose as compared with IV
Hepatic drug metabolism involves the conversation of water soluble into lipid soluble.
False. Lipid into water soluble soluble.
Alkalizing the urine enhances excretion of acidic drugs.
True
Facilitated passive diffusion is a saturable process
True
The plasma-protein bound fraction of a drug undergoes glomerular filtration.
False. Glomerular filtration: molecules below 20 kDa pass into filtrate. Drug must be free, not protein
bound.
The time required to reach steady state is approximately 2 half lives.
False. Approximately 4/5
Second messengers relay signals from receptors on the cell surface to target molecules inside the cell
True
Bio availability refers to the elimination rate of a drug per unit time
False. Bioavailability is the fraction if drug absorbed into systemic circulation.
Rifampicin is a cytochrome P450 enzyme inhibitor
False. Rifampacin is a cytochrome P450 enzyme inducer.
lipophilic drugs have a high volume of distribution
True
