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Pharm > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

Pharmacokinetics

A

Factors that contribute to controlling concentration of a drug at an action site

Absorption (bioavailability)
Distribution
Metabolism (/clearance)

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2
Q

Bioavailaibiilty

A

Fraction or % of a drug that enters the circulation after the first pass effect

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3
Q

Bioavailable dose

A

mg or mg/kg of a drug that enters the circulation after first pass effect

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4
Q

Factors for deciding the appropriate route of administration

A

Prospects for compliance
Speed of absorption
Potential for therapeutic effects with local delivery

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5
Q

Enteral routes

A

Entering via intestine

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6
Q

Parenteral routes

A

Entering outside the intestine

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7
Q

Oral administration

A

Pros - convenient, safe, economical, higher compliance, can induce vomiting if overdose
Cons - first pass effect, irregular absorption due to pH/food, not practice if patient is vomiting

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8
Q

Advantage of sublingual administration

A

Avoids first pass effect

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9
Q

Rectal administration

A

Pros - can be used for vomiting patient or where oral impractical

Cons - absorption can be irregular, slower (typically)

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10
Q

Intravenous administration

A

Pros - instantaneous, Endothelia more tolerant of irritating solutions

Cons - toxicity?, not readily reversible, requires expertise, repeat injection —> lose patency of veins

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11
Q

Subcutaneous administration

A

Can be manipulated for fast or slow administration

Common for vaccines

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12
Q

Intramuscular injection

A

Often slow

Can be painful

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13
Q

Instantaneous administration

A

IV
Inhalation
Nasal

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14
Q

Slow administration

A

Rectal
transdermal
IM

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15
Q

Other routes of administration

A

Intrathecal, intraocular, intraosseous

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16
Q

Factors affecting bioavailability

A

Route of administration
Physicochemical properties of drug
Physiology of patient

17
Q

Methods of crossing membranes

A

Passive diffusion (lipid soluble)
Carrier-mediated transport (charged/polar molecules)

18
Q

Weak acids will be absorbed …

A

In an acidic environment

19
Q

Weak bases will be absorbed …

A

In a basic environment

20
Q

Factors that affect distribution

A

Rate of absorption (charge, lipophilicity, pH, amount in circulation, surface area of compartment)

pH gradients

21
Q

Weak acids will accumulate in …

A

Basic compartments

22
Q

Weak bases will accumulate in …

A

Acidic compartments

23
Q

Volume of distribution

A

Hypothetical/apparent volume of plasma into which a drug distributes if drug were only distributed in plasma

= Bioavailabile dose / concentration of drug in plasma

24
Q

Volume of distribution > 0.6 L/kg indicates

A

Drug accumulated in non-aqueous environment (fat, organs)

25
Q

Volume of distribution &laquo_space;0.6 L/kg indicates…

A

Drug is being accumulated in blood compartments; does not have access to non-plasma compartments

26
Q

Majority of drugs are metabolized by …

A

First order kinetics

27
Q

First order kinetics

A

Rate of metabolism is proportional to concentration of drug

(I.e. the same amount of drug is metabolized over a given interval)

No saturation effect

28
Q

Clearance

A

Metabolism + elimination

Volume of plasma that is cleared of a drug per unit time (normalized to body weight - ml/min per kg)

29
Q

Two compartment pharmacokinetic model

A

A drug may enter a particular compartment quickly —> then redistribute to other areas of the body - this results in an initial rate, followed by a secondary rate

Starts out step —> quickly leaves central compartment (most heavily perfused) —> redistributes —> clears more slowly from the system (peripheral compartment)

Change in concentration = some of two first order decay processes

30
Q

Repeated administration of a drug

A

Four doses required to reach steady state

Peak/troughs average over plateau concentration

31
Q

To avoid the ramp up to the plateau concentration of a drug

A

Administer a loading dose (initial high dose)

32
Q

When an enzyme system is saturated elimination follows…

A

Zero-order kinetics

33
Q

Zero order kinetics

A

Same amount of drug is eliminated in any time interval (as opposed to same fraction under normal conditions)

Common example = alcohol

34
Q

Factors that may impact pharmacokinetics

A

Age
Weight
Disease states
Drug-drug interactions
Polymorphisms
Species

Pharm (10 decks)

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