pharmpath Flashcards
(90 cards)
Lineweaver-Burk plot. What does the X intercept mean and what does the Y intercept mean?
X intercept is 1/-Km. So the more to the right that is, the bigger Km is, and the lower the affinity. Y intercept is 1/Vmax. The higher that is, the lower Vmax is. Can remember this because V looks kind of like a Y.
Bioavailabilty equation
Fraction of drug that reaches circulation unchanged. F = 100% IV. Area under oral curve/ area under IV cure (227)
Volume of distribution equation
Amount of drug in body/ plasma concentration of drug.
What is the range for a low volume of distribution and what are some drug types?
Low means mostly in the blood. 4-8 L. Large, charged molecules, plasma protein bound
Where do medium volume of distribution drugs go and what are some drug types?
Medium go to the ECF. Small, hydrophilic molecules. Small so can get through, but not lipophilic so can’t really spread too far
Where do high volume of distribution drugs go and what are some drug types?
Go to all tissues. Small, lipophilic, bound to tissue proteins
Half life equation. What can you calculate from half life?
t1/2 = (.7 x Vd) / CL
How long does a drug infused at a constant rate take to reach steady state?
4-5 half lives
Clearance equation
Clearance = rate of elimination of drug/ concentration of drug in plasma. = Vd x Ke (elimination constant) –> amount of drug in body x elimination constant/plasma concentration of drug
Loading dose equation
Cp x Vd / F. Cp = target plasma concentration. So for loading, need to take into account the spread and how much is going to get hit by first pass. F is how much will make it, so the bigger F is, the lower dose you need. The bigger Vd, the higher dose you
Maintenance dose equation
Cp x CL/F. Now we are maintaining, so have to increase dose with clearance and decrease dose if more makes it through first pass.
Zero order vs first order elimination
Zero: constant amount eliminated no matter what the concentration. Called capacity dependent elimination (maxed out already so doesn’t matter what concentration is). First order: constant fraction eliminated. Called flow dependent elimination
How can you treat phenobarbital, MTX, and aspirin overdose all at once?
Bicarb. These are all weak acids and can get trapped in basic environments by ionizing them.
How can you treat an amphetamine OD?
Ammonium chloride. Weak base, can trap with acid.
What do phenytoin, ethanol, and aspirin have in common?
Zero order kinetics at high or toxic concentrations
Phase I vs Phase II metabolism
Phase I is P450, does reduction, oxidation, hydrolysis that yields slightly polar, water-soluble metabolites (often still active). Phase II does conjugation and yields very polar, inactive metabolites that are excreted. This is where slow acetylators come
Therapeutic index
Median lethal dose/ median effective dose. Safer drugs have higher TI’s, takes a way bigger lethal dose than effective dose
Therapeutic window
Range of minimum effective dose to minimum toxic dose.
What type of G protein does mydriasis via pupillary dilator muscle contraction?
Alpha 1 –> Gq
What type of G protein decreases HR and contractility of atria?
M2 is heart –> Gi
What kind of G protein increases sweat?
M3 –> Gq. Remember, this one is a muscarinic carrying out sympathetic activity!
What type of G protein does intestinal and bladder sphincter muscle contraction?
Apha 1 –> Gq
What kind of G protein relaxes renal vascular smooth muscle?
D1 –> Gs
What kind of G protein responds to ADH with increased vascular smooth muscle contraction?
V1 –> Gq
