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SRNAClinical Practicuum Prep > Pharmacokinetics Concepts > Flashcards

Pharmacokinetics Concepts Flashcards

1
Q

Easy way to make sense of this Pharmacokinetics concepts

A

Drugs goes in (front-end kinetics)

Drugs goes out (Back end kinetics)

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2
Q

Drugs given via IV not affected by that part of pharmacokinetics?

A

Absorption

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3
Q

What is bioavailablity?

A

Amount of drug reaching systemic circulation UNCHANGED.

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4
Q

What is the key concept of ABSORPTION?

A

Transfer from depot to Systemic Circulation

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5
Q

What are some of the depot organs?

A

Stomach, lungs, muscle tissue.

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6
Q

What plays an important role in the rate of absorption

A

Physical properties of the drug.

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7
Q

2 factors determine polarity of the molecule

A

pKa in relation to physiologic pH

DIFFUSION depends on concentration gradient between the depot and the systemic circulation (FIRST-ORDER KINETICS)

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8
Q

Absorption of Inhaled anesthetics depends on

A

Blood-Gas Partition coefficient

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9
Q

What is Blood Gas partition coefficient?

A

Describes concentration in Blood COMPARED TO that in the ALVEOLAR gas at equillibrium
(ex: blood concentration of drug is 10 , concentration in alveolar gas is 5 –> Partition coefficient is 2 (10/5)

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10
Q

What does a HIGH Blood partition coefficient means?What does it mean clinically?

A

A lot of drug must be absorbed before equillibrium occurs.

Clinically means it will take longer for the desired effect to be achieved.

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11
Q

Partition coeffecient is dependent on which physical property?

A

Temperature

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12
Q

What is the formula of VOLUME of distribution

A

Vd = dose / plasma concentration

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13
Q

Volume of distribution is property of a drug that describes its ability to do what ?

A

Ability to distribute in human body

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14
Q

How is the CENTRAL VOLUME Of DISTRIBUTION calculated?

Central Vd is

A

Inject drug IVsly –> then measure arterial concentration
ELUSIVE concept easy way:
Central Vd–> volume in lungs, hearts, great vessels and venous volume proximal to injection site.

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15
Q

What is peripheral volumes of distribution?

A

solubility in the tissues compared to that of plasma

each tissue have own peripheral Vd

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16
Q

Vd at steady states describes

A

tissue solubility at steady state for both central and peripheral

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17
Q

BACK end Kinetics: CLEARANCE

A

Process of removing drugs from a tissue

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18
Q

BACK END kinetics : clearance 2 ways

A
  1. Permanent removal (usually by hepatic Metabolism)

2. Intercompartmental Clearance (distribution clearance) from plasma to TISSUE

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19
Q

Most drugs metabolized by

A

Hepatic Biotransformation

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20
Q

What are the phase 1 Reactions?

A

Oxidation
Reduction
Hydrolysis

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21
Q

What is a phase 2 reaction?

A

Conjugation

22
Q

2 reactions using CYP450

A

Oxidation and reduction

23
Q

2 important enzymes inducers (RPPCSC)

A 
Rifampin
Phenytoin
Phenobarbital 
Cigarette smoking
Carbamezapine (Tegretol)
24
Q

2 Important inhibitors

A

CCBs

AMIODARONE

25
Q

What does CONJUGATION really do?

A

They combine a hydrophobic molecule to a POLAR group so that they can be easily excreted by the kidneys

26
Q

After conjugation, those molecules are usually Inactive. What is the exception to that rule? Explain and why it is important?

A

MORPHINE
Morphine is metabolized into 2 metabolites: Morphine-3-Glucuronide (M3G) and Morphine-6- Glucuronide (M6G) (more potent than morphine itself
Important for patient with renal disease as they may not be able to metabolize the MORE POTENT

27
Q

What other drugs has an active metabolite of equal potency?

A

Midazolam ( Versed)

28
Q

In anesthesia, It is assumed that

A

rate of metabolism iS PROPORTIONAL to concentration (but remember is some cases liver may become saturated)

29
Q

Formula to calculate rate of metabolism

A

Rate = Q (C inside - C outside)
Q blood flow to liver
C inside : concentration flowing in
C outside: concentration flowing out

30
Q

Another important concept in liver metabolism is _________Calculated as

A

Hepatic Extraction ratio: liver not able to remove the molecule of a drug from plasma
ER = (C in - C out)/ C in
Clearance = Q x ER

31
Q

High extraction Ratio means :

The metabolism of such drug said to be “ ____”

A

Clearance depends on blood flow to the liver (amount of drug metabolized will depend on liver blood flow)
Flow limited

32
Q

Example of a drug with high ER

A

Propofol

33
Q

Why is the concept high ER important for Anesthetists?

A

Anesthetics decrease HEPATIC BLOOD FLOW

34
Q

Low extraction Ratio means

The metabolism of such drug said to be “ ____” :

A

Clearance DOES NOT depend on blood flow to the liver (amount of drug metabolized LESS depend on liver blood flow)
Capacity limited

35
Q

Example of a drug with LOW ER

A

Alfentanyl

36
Q

ONLY Major anesthetic that undergoes 80% renal excretion?

A

PANCURONIUM

37
Q

Provides a good summary of determining factors for renal function ______used to calculate___

A

Cockcroft-Gault Equation; GFR

38
Q

What is the Cockcroft-Gault Equation

A

CrCl = 140-age (yr) x weight (kg) / (72 x serum Creatinine)

39
Q

Renal clearance relationship with age is

A

INVERSELY PROPORTIONAL

40
Q

Unique Metabolism of anesthetic drugs: Hoffman degradation

A

Cisatracurium

Atracurium (plasma)

41
Q

Unique Metabolism of anesthetic drugs: PSEUDOCHOLINESTERASES (new name butylcholinesterase)

A

Succinylcholine

Mivacurium (plasma )

42
Q

Unique Metabolism of anesthetic drugs: NONSPECIFIC ESTER HYDROLYSIS

A

Remifentanyl

ATracurium

43
Q

What are 2 major Plasma protein for BINDING of ANESTHETIC drugs?

A

Albumin

Alpha–1-Acid Glycoprotein

44
Q

Why is protein binding important to consider?

A

because the only the unbound portion of the drug can exhibit pharmacological effect

45
Q

Protein binding depends on ____________ NOT on

A

Concentration of plasma protein

NOT concentration of the drug

46
Q

A decrease in protein binding leads to _______Concentration of the free form of the drug

A

INCREASE

47
Q

Protein binding and Vd

A

Decrease in protein binding lead to increase free drugs which will equillibrate with peripheral tissue. This will cause a decrease in plasma concentration and –> decrease Vd

48
Q

What does ZERO order kinetic means

A

Also knonw as LINEAR
Human body clear at constant RATE NO MATTER THE DOSE
Ex: ETHANOL, ASA,

49
Q

What does FIRST ORDER KINETIC MEANS

A

Dose dependent

CLEARANCE PROPRTIONA TO concentration

50
Q

3 compartment models

A

Divide Body into 3 parts:
1.central compartment (plasma)- 100% in plasma f/b –>
2. Rapid equilibrating compartment: vessel rich Brain, GI tract
Slow equilibration compartment : vessel poor tissues, fats

SRNAClinical Practicuum Prep (21 decks)

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