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49 Cards in this Set

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What does a Scatchard plot measure?
Measures affinity of a ligand for a receptor and the number of receptors per mg of protein
Affinity...?
Affinity = -1/Kd = slope
Bmax...?
Bmax = number receptors per mg of protein

Bmax = x-intercept
What is the usual basis for idiosyncratic drug reactions?
Usually a genetic basis.
What happens if someone has a plasma pseudocholinesterase deficiency?
The NMB caused by succinylchonile lasts hours instead of minutes
Idiosyncratic drug rxn with barbituates?
Produce excitation and anxiety instead of sedation in older patients.
Idiosyncratic drug rxn with older antihistamines?
The older antihistamines (e.g. diphenhydramine) cause excitation instead of sedation in very young children and older patients.
Idiosyncratic drug rxn with ASA and other NSAIDs?
Precipitate an anaphylactic-like reactions (a.k.a. aspirin hypersensitivity) in patients with nasal polyps.

Blockade of PG synthesis by the NSAID shunts all the arachidonic acid to leukotriene synthesis
-- LT's cause rhinoconjunctivitis, angioedema and urticaria.
Idiosyncratic drug rxn in pts with G6PD deficiency?
Hemolytic anemia is produced by:
-- primaquine
-- isoniazid
-- sulfonamides
-- nitrofurantoin
-- eating fava beans
Idiosyncratic drug rxns in pts that are slow acetylators?
SHIP drugs exhibit toxicity in slow acetylators

SULFAPYRIDINE
-- hemolytic and aplastic anemia
-- hepatic damage

HYDRALAZINE
-- SLE-like syndrome

ISONIAZID
-- hepatic damage
-- peripheral neuropathy (treat w/ pyridoxal phosphate - Vit B6)

PROCAINAMIDE
-- SLE like syndrome
What causes malignant hyperthermia?
A gene defect prevents Ca++ from being sequestered correctly in the SR of skeletal muscle.

Anesthesia w/ volatile anesthetic agent (HALOTHANE) plus admin of SUCCINYLCHOLINE causes massive release of Ca++
-- masseter muscle spasm
What does a Scatchard plot measure?
Measures affinity of a ligand for a receptor and the number of receptors per mg of protein
Affinity...?
Affinity = -1/Kd = slope
Bmax...?
Bmax = number receptors per mg of protein

Bmax = x-intercept
What is the usual basis for idiosyncratic drug reactions?
Usually a genetic basis.
What happens if someone has a plasma pseudocholinesterase deficiency?
The NMB caused by succinylchonile lasts hours instead of minutes
Idiosyncratic drug rxn with barbituates?
Produce excitation and anxiety instead of sedation in older patients.
Idiosyncratic drug rxn with older antihistamines?
The older antihistamines (e.g. diphenhydramine) cause excitation instead of sedation in very young children and older patients.
Idiosyncratic drug rxn with ASA and other NSAIDs?
Precipitate an anaphylactic-like reactions (a.k.a. aspirin hypersensitivity) in patients with nasal polyps.

Blockade of PG synthesis by the NSAID shunts all the arachidonic acid to leukotriene synthesis
-- LT's cause rhinoconjunctivitis, angioedema and urticaria.
Idiosyncratic drug rxn in pts with G6PD deficiency?
Hemolytic anemia is produced by:
-- primaquine
-- isoniazid
-- sulfonamides
-- nitrofurantoin
-- eating fava beans
Idiosyncratic drug rxns in pts that are slow acetylators?
SHIP drugs exhibit toxicity in slow acetylators

SULFAPYRIDINE
-- hemolytic and aplastic anemia
-- hepatic damage

HYDRALAZINE
-- SLE-like syndrome

ISONIAZID
-- hepatic damage
-- peripheral neuropathy (treat w/ pyridoxal phosphate - Vit B6)

PROCAINAMIDE
-- SLE like syndrome
What causes malignant hyperthermia?
A gene defect prevents Ca++ from being sequestered correctly in the SR of skeletal muscle.

Anesthesia w/ volatile anesthetic agent (HALOTHANE) plus admin of SUCCINYLCHOLINE causes massive release of Ca++
-- masseter muscle spasm
Signs/symptoms of malignant hyperthermia?
Increased BP, HR

Muscle contraction w/ hyperthermia

Lactic acidosis

Cardiac dysrhythmias
Treatment of malignant hyperthermia?
Dantrolene Na which prevents the release of Ca++ from the SR
What causes neuroleptic malignant syndrome?
Etiology NOT related to malignang hyperthermia

Produced by rapid blockade of central DA receptors w/ the typical antipsychotics drugs like HALOPERIDOL
Signs/symptoms of neuroleptic malignant syndrome?
Resembles severe Parkinson's dx w catatonia
-- EPS
-- stupor
-- hyperthermia
-- increased CPK, myoglobinuria, ARF
Treatment of neuroleptic malignant syndrome?
dantrolene Na + bromocriptine (D2 receptor agonist)
Formula to calculate estimated plasma concentration at zero time (Cpo)?
Cpo = (Xo x F)/Vd

Xo = dose (mg)
F = bioavailability (no units); when given i.v., F = 1.0
Vd = volume of distribution (L or L/kg)
Formula to calculate loading dose (XL)?
XL = (Cp x Vd)/F

Cp = plasma concentration (mcg/ml or mg/L)

Vd = volume of distribution (L or L/kg)

F = bioavailability
Formula to calculate fractional rate of elimination (k)?
k = 0.7/half-life
Formula to calculate half-life?
half-life = Vd/Cl

Vd = volume of distribution (L or L/kg)

Cl = clearance (ml/min or L/h)
Formula to calculate clearance (Cl)?
Cl = rate out/Cp

Cp = plasma concentration (mcg/ml or mg/L)
Steady state is...?
at Cpss: rate in = rate out
mcg/ml = ?
mg/L
Cpss = ?
4 x half-life
Clinical: two patients who weigh the same and have normal renal and hepatic fxn are given a single dose of a drug.

Old patient Cpo = 14mcg/ml
young pt Cpo = 10mcg/ml

Why is the Cpo different?
Will the half-life of the drug be different in the two patients?
The older patient has a smaller Vd (volume of distribution), or the younger patient has a larger Vd

Yes: Since half-life = Vd/Cl, and since the Vd in the older pts is smaller, the drug will have a shorter half-life in the older pt
How do simultaneous changes in F and Cl affect the Cp?
Remember: Cpss is directly proportional to F, and Cpss is inversely related to Cl (write in chart comparison)
Remember the XL depends on the Vd, and the Xm depends on the Cl.

A drug is 50% cleared by the liver and 50% cleared by the kidneys. The normal maintenance dose is 100mg/day.

1. What is the Xm if renal fxn decreases by 50%?

2. What is the Xm if renal fxn ceases?
1. 75mg/day

2. 50mg/day
Almost all drugs follow linear kinetics, for example...?
If you double the dose, it will double the CP
A patient is given a dose of 100mg and the Cp is 10mg/L. What dose would you have to give to achieve a Cp of 30mg/L?
300mg
Favorite inducers of CYP450?
phenobarbital
phenytoin
carbamazepine
nicotine
chronic EtOH consumption
Favorite inhibitors of CYP450?
erythromycin
ketoconazole

The time is ripe for them to ask about grapefruit juice and an inhibitor of CYP450:
-- the question will probably involve decreased clearance of a calcium channel blocker

The question may not ask about the Cp:

rather, the effect of the drug will be decreased (induction of CYP450) or increased (inhibition of CYP450)
First order elimination? (add graph)
LINEAR

A constant fraction of drug is eliminated per unit of time
Zero order elimination? (add graph)
a constant AMOUNT of drug is eliminated per unit of time
What is an α-β curve?
This shows a drug which follows a two compartment model

α phase - represents the distribution of drug btwn peripheral and central compartments and has NOTHING to do with drug clearance

β-phase - the elimination phase which is used for ALL kinetic calculations
-- ex: determ of half-life
What is a 0-1 curve?
A drug which begins w/ zero elimination which gives way to first-order elimination after the Cp falls below some critical value

The drug is ethanol.

Above a certain Cp falls below a certain value, alcohol dehydrogenase is no longer saturated and the elimination of ethanol becomes first-order.
The renal clearance of acidic drugs can be increased by...?
Ex: ASA

making the urine alkaline by admin of sodium bicarb or carbonic anhydrase inhibitor such as ACETAZOLAMIDE

The lower the pKa of the acidic drug, the greater the increase in renal clearance when the urine is made alkaline
The renal clearance of basic drugs can be increased by...?
Ex: amphetamine

making the urine acidic by admin of ammonium chloride

The higher the pKa of the basic drug, the greater the increase in renal clearance when the urine is made acidic.
Only _______ drug exerts a pharmacologic effect.
Free

Decreased plasma protein conc (eg. albumin) increases the fraction of free drug in plasma