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Km
concentration of substrate where enzyme is going at a 50% rate
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Vmax
the point at which increasing the substrate does not make the enzyme go faster because it is maxed out
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Michaelis-Menten plot
- Km = x axis at point on slope where y = 1/2Vmax
- Vmax = y value where it flattens out

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Lineweaver-Burk plot
- Km = -1/xint
- Vmax = +1/yint
- increasing abs(xint) reduces Km
- increasing yint reduces Vmax

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reversible competitive inhibitor
- binds active site/resembles substrate
- Vmax unchanged (just takes substrate)
- Km increased (=takes more substrate)
- reduces potency
- no effect on efficacy
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irreversible competitive inhibitor
- binds active site/resembles substrate
- Vmax reduced (some of enzyme is deactivated because it bound the wrong thing)
- Km unchanged (the enzyme that still works is doing fine)
- reduces efficacy
- no effect on potency
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noncompetitive inhibitor
- binds alternate site on enzyme to inhibit it
- Vmax reduced (some of enzyme is deactivated)
- Km unchanged (the enzyme that still works is doing fine)
- reduces efficacy
- no effect on potency
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oral bioavailability
- depends on absorption
- hepatic destruction
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volume of distribution
- lowest for large charged molecules/plasma protein bound
- small greatest for lipophilic esp if tissue protein bound

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clearance
- depends on cardiac, hepatic, renal function

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half life
- time to reduce amount of drug in body by half
- 1st order kinetics takes 4-5 half lives to reach steady state

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loading dose
- NOT affected by renal or liver disease

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maintenance dose
- affected by renal/liver disease
 - Cp=target [drug]plasma
- for a continuous does just move tau to the bottom of the maintenance dose side and you're calculating a rate instead
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additive drug interaction
- sum of the two effects is the total effect
- aspirin and acetaminophen
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permissive drug interaction
- presence of A is required for full effect of B
- cortisol on catecholamine responsiveness
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synergistic drug interaction
- effect of A and B is greater than the sum
- clopidogrel and aspirin
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tachyphylactic drug interaction
- acute decrease in response to drug after initial/repeated administration
- MDMA
- LSD
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zero order elimination examples
- phenytoin
- ethanol
- aspirin (high/toxic concentrations)
- constant elimination regardless of Cp
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weak acid examples
- phenobarbital
- methotrexate
- aspirin
- treat with bicarb (trapping it in ionized state)
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weak bases
- amphetamines
- TCAs
- treat with ammonium chloride (trapping in ionized state)
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phase I metabolism
- reduction, oxidation, hydrolysis via P-450
- geriatric patients lose phase I first
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phase II metabolism
- sulfation, acetylation, glucuronidation, glutathione conjugation, glycine conjugation, methylation
- slow acetylators have more side effects
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efficacy
- how much of a response a drug can cause
- regardless of how much drug you have to give to generate that response (potency)
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EC50
- measure of potency
- not related to partial/full agonism
- how much drug you need to get half the max response
- low EC50=high potency
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competitive antagonist
- binds to receptor
- reduces potency not efficacy
- increase EC50 (increase dose required to generate same effect)
- can also be overcome by increasing substrate
- dizepam (agonist) and flumazenil (comp antag)
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noncompetitve antagonist
- binds to receptor
- reduces efficacy not potency
- cannot be overcome by increased drug or substrate
- NE (agonist) and phenoxybenzamine (non comp antag)
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partial agonist (alone)
- less effective
- potency could be higher or lower than full agonist
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therapeutic index
- TI (therapeutic index)
- measure of safety
 - safer drug has higher TI
- LD50 replaces TD50 in animal studies
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