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Pharmacology > Pharmokinetics (Exam 1) > Flashcards

Pharmokinetics (Exam 1) Flashcards

1
Q

How do drugs reach their site of action

A

rarely administed at site of action
most have to travel through several barriers

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2
Q

How do drugs permeate into the cell (4)

A

Aqueous diffusion
lipid diffusion
special carriers (channels)
endo/exocytosis

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3
Q

What can and cannot permeate via aqueous diffusion

A

water soluble, goes from high to low conc, large molecules can

highly charged, bound to large proteins (carriers)

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4
Q

How do drugs permeate through lipid diffusion

A

the have to be lipid soluble and have no charge
move high to low
consider drugs that become charge or uncharge based on pH and pKa

limiting factor for drugs because it has to cross many lipid barriers

ex cholesterol, steroids

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5
Q

How do special carriers work

A

bind to molecule bring into the cell and maybe cross a barrier or vice verssa

resistant drug: cancer can pump drug back out
blood brain barrier keeps everythin out
liver takes everything in

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6
Q

How does the Norepi transporter (NET) work and what drugs affect it

A

cell releases NE into the NMJ and opens channels later reuptakes NE
cocaine blocks NET from reuptaking NE and dopamine to stay in the synapse longer

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7
Q

What is the difference between endo and exocytosis?

A

endo membrane engulfments
-clathrin pits
exo vesicle merges with membrane

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8
Q

What is Volume of distribution (Vd)

A

the space available in the body to contain the drug
how much did we give them vs how much is in the blood

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9
Q

What is clearance (CL)

A

ability of the body to eliminate the drug
elimination is not the same of clearance

CL is constant and eliminiation chages based on CL

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10
Q

How is Vd calculated

A

amt of drug given (mg) divided by the initial drug concentraion (mg/L) = (L)

just in blood

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11
Q

What is the difference between blood volumes in whole blood vs plasma

A

Whole blood 0.08L/kg or 5.6 L/70kg
Plasma 0.04L/kg or 2.8L/70kg
plasma is less

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12
Q

What does it mean if you have a high Vd?

A

less amount of drug in the blood

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13
Q

Example of a drug that has a high Vd

A

Hydroxychloroquine
Vd= 10,000L/70kg
% in blood= (5.7L/70kg)/(10,000L/70kg)
=0.00056 or 0.056%

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14
Q

How do you calculate the dose

A

Vd x Target Concentration (TC)

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15
Q

What happens to a drug concentration in the blood when given a bolus of a drug?

A

Concentration spikes in the blood, then gets distributed, then over time get eliminated

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16
Q

What is Clearance (CL)

A

predicts the rate of elimination in relation to drug concentration

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17
Q

How do we calculate CL

A

Rate of Elimination (ROE)=CL/Concentration in blood

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18
Q

What factors are considered in systemic CL

A

renal, liver, and other

19
Q

What is first-order elimation

A

clearance is constant and ROE varies with concentration
applies to most drugs

20
Q

What is zero-order elimination

A

rate of elimnation is constant and CL varies
all elimination mechanisms are saturated, so much of the drug can get eliminated

21
Q

How does first order become zero order elimination

A

at high enough concentration you will reach the Vmax of how fast you can eliminate.
go from first order to zero
Michaelis-menten plot speed of how fast you can get rid of the drug

22
Q

Important drugs that do reach zero order

A

apsirin, alcohol, phenytoin

23
Q

What is a high extraction drug

A

a drug that passess through an organ a large portion is removed before it gets into systemic circulation

24
Q

How is organ clearance determined?

A

Cl organ=blood flow x extraction ratio
=Q(flow of blood) E (extraction ration)
=Q x (Cin-Cout/Cin)
=percentage

25
Q

How do we determine if a drug has a high vs low extraction ratio

A

> 0.7 = high
0.3-0.7 = intermediate
<0.3 = low

26
Q

How does extraction ratio affect blood flow and clearance

A

E is high, Q is low, Cl is low
E is low, Q high, Cl low
E is high, Q high, Cl is high
E is low, Q is low, Cl is low

27
Q

What is Half-Life (T1/2) and what is affeted by it

A

the time it takes the body to get rid of 1/2 the concentraton of the drug
T1/2= 0.7xVd/CL

10mg half life after 4 hrs reduced to 5mg after 4 hours reduced to 2.5mg

28
Q

What does it mean to give a drug in steady state

A

giving a drug enough to replace what its eliminating and accumulates until we get the TC in the plasma
- TC based on trial and error

29
Q

How long does it take for a drug to reach TC in the blood vs out of it

A
  • It takes 4 half lives to reach the full TC if you do not give a bolus
  • it takes 4 half lives after stopped to return to 0% in the plasma
30
Q

What can affect the half life of a drug

A

disease state of organ (kidney, liver, etc)

31
Q

What is accumulation in terms of half lives

A

If you dont wait 4 half-lives the concentration in the plasma increases and can lead to toxicity quickly

32
Q

What is Bioavailability (F)

A

the % of the drug that reaches systemic circulation
IV is 100%
oral, IM, SQ, inhalation vary

33
Q

What factors affect bioavailability

A

the physical properties of the drug (hydrophilicity, pKa, solubility)
formulation/rate
health of GI
interaction with other drugs
overall health or disease state
circadian rhythm

33
Q

What is First-Pass elimination

A

oral drug is absorbed in the small intestine and has many blood vessels that form the hepatic portal system (series of capillaries that join together form a vessel then branch down into more capillaries)
Drugs enter the GI -> liver before they go into systemic circulation
The liver can biotransformed become more active or less active
High absorption in gut doesnt mean high bioavailaility

34
Q

How can the First Pass elimination be bypassed

A

different route: IV, IM, SC
inhalation has its own metabolism
oral drugs can be given SL or transdermal
rectal suppositories but can migrate up

35
Q

What can affect the time of a drugs effect

A

immediate: effects increases and concentration increases (sigmoid curve)
delayed: associated with distribution or protein turnover (trnscription/translation)
effects can be cumulative

36
Q

What is the Target Concentration

A

concentration that will produce desired effect
pharmokinetic factors affect dose concentration
- individualized to determine dose
TC is calculated by the manufactuer

37
Q

What is maintenance dosing

A

maintain steady state of drug by giving enough to replace eliminated drug
Clearance is the most important factor
we want dosing rate = clearance x target conentration

38
Q

How do we calculate maintenace does for drugs with <100 % bioavailability

A

Dosing rate = dosing rate (cacl)/F (bioavailability)

39
Q

What is intermittent dosing

A

maintenance dose = dosing rate x dosing interval (hr)

40
Q

What is the purpose of a loading dose

A

need to reach the steady state quickly
consider Vd
LD=Vd x TC
need to give slow because can be toxic need time for distribution

41
Q

What is threapeutic drug monitoring

A

peak and trough test
blood draw
- peak: 5-10 after administration IV
- trough: 30 min prior to nest dose
- random: anytime between
Clearance is most important factor
- kidney and liver health
Blood flow
- albumin concentration
- other drugs causing proteins to bind or unbind

-

42
Q

How do we calculate Vd for drugs that do not penetrate fat

A

Use ideal body weight

43
Q

How do we estimate kidney function

A

creatinine clearance
muscle produces same amount of creatinine get some idea of kidney function

Pharmacology (7 decks)

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