Km is inversely related to...
the affinity of the enzyme for its substrate.
Vmax is directly proportional to...
the enzyme concentration.
Most enzymatic reactions follow...
a hyperbolic curve (follow Michaelis-Menten kinetics); however, enzymatic reactions that exhibit a sigmoid curve usually indicate cooperative kinetics (ex. hemoglobin).
On a Lineweaver-Burk plot, increased y-intercept means...
On a Lineweaver-Burk plot, the further to the right the x-intercept...
the greater the Km and the lower the affinity.
Slope of a Lineweaver Burk-plot =
x-intercept of Lineweaver-Burk plot =
y-intercept of Lineweaver-Burk plot =
On a Lineweaver-Burk plot, competitive inhibitors...
cross each other competitively, whereas noncompetitive inhibitors do not.
Inhibitors that resemble substrate
Competitive (both reversible and irreversible)
Inhibitor that is overcome by increased substrate
reversible, competitive inhibitors
Competitors that bind the active site
competitive, both reversible and irreversible
Effect of competitors on Vmax
Competitive reversible: unchanged Competitive irreversible: decreased Noncompetitive: decreased
Effect of competitiors on Km
Competitive reversible: increased Competitive irreversible: unchanged Noncompetitive: unchanged
Pharmacodynamics of competitors
Competitive reversible: decreased potency Competitive irreversible: decreased efficacy Noncompetitive: decreased efficacy
the effects of the body on the drug (absorption, distribution, metabolism, excretion)
the effects of the drug on the body (receptor binding, drug efficacy/potency, toxicity)
Bioavailability (F) is the...
fraction of administered drug that reaches the systemic circulation unchanged.
For an IV dose, F =
100%. Orally, F typically is
The volume of distribution (Vd) is the...
theoretical volume occupied by teh total absorbed drug amount at the plasma concentration.
The apparent volume of distribution of plasma protein boudn drugs can be altered by...
liver and kidney disease becasue decreased protein binding will increase Vd.
(amount of drug in the body)/(plasma drug concentration)
Vd is usually low if the drug is in the...
blood. Drug types include large, charged molecules that are plasma protein bound.
Vd is medium if the drug is in the...
ECF. Drug types include small hydrophilic molecules.
Vd is large if the drug is in...
all tissues including fat. Drug types include small lipophilic molecules, especially if bound to tissue protein.
Half-life (t1/2) is the...
time required to change the amoun tof drug in the body by 1/2 during elimination (or constant infusion).
To reach steady state, a drug infused at a constant rate takes...
4-5 half lives.
(.693 x Vd)/CL
Clearance (CL) is the...
volume of plasma cleared of drug per unit time. It may be impaired by defects in cardiac, hepatic or renal function.
(rate of elimination of drug)/(plasma drug concentration) = Vd x Ke