[6] Pharmacokinetics Flashcards by Jp Reyes

Definition: Pharmacokinetics

Effect of the body on the drugs

kinEtics : admE (Absorption, Distribution, Metabolism, Excretion)

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Routes of Administration

Enteral

Parenteral

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Examples of Enteral Administration

Oral
NGT
Gastrostomy Tube

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Examples of Parenteral Administration

Intravenous
Intramuscular
Subcutaneous
Intradermal
Topical

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[Better or Worse Arbsorption]

Non-Ionized

Better

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[Better or Worse Arbsorption]

Small Molecules

Better

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[Better or Worse Arbsorption]

Lipid-Soluble

Better

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[Better or Worse Arbsorption]

Ionized

Worse

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[Better or Worse Arbsorption]

Large Molecules

Worse

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Dopamine and Serotonin penetrate brain tissue poorly, however these precursors enter with relative ease.

L-Dopamine

5-Hydroxytryptophan

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Used to treat Parkinson’s Disease

L-Dopa

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Define: Volume of Definition

Hypothetical Volume

Not the same as PV, BV, Interstitial Volume, Intracellular Volume, Extracellular Volume

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Formula: Volume of Distribution

Dose Administered / Concentration

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[T/F] If Drug X is metabolized into an inactive metabolite and this inactive metabolite is excreted by the kidneys, the mode of elimination is both metabolism and excretion

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Define: Phase I Reactions

Functionalization Reactions

Oxidation, Reduction, and Hydrolytic Reactions

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Define: Phase II Reactions

Conjugation Reactions

Conjugated to polar groups:

Glucorinidation, Sulfation, Acetylation

What is the initial molecule for hormones?

Cholesterol

Which cytochromes handles the most of P450 Metabolism?

CYP3A4 (50%)

Recent data says it’s about 33%

How long does it take for an inhibitor to take effect?

About a week

Is Grapefruit Juice an inhibitor?

Yes, a yummy one.

Define: Phase 3 Metabolism

Not metabolism perse, no biotransformation occurs.

This is a transporting “phase”

What kind of a pump is P-Glycoprotein?

Efflux Pump

Define: Enterohepatic Recirculation

Compound is conjugated in the liver
Excreted in the bile
Deconjugated in the intestine
Reabsorbed in circulation

Physiologic Significance of Enterohepatic Recirculation

95% of Bile Salts are reabsorbed and used for cholesterol synthesis

Allows for the prolonging of duration of action of a drug

Excretion of drugs by the liver is usually through?

Biliary excretion

Differentiate: Metabolism and Excretion

When a drug is excreted, it is untouched not a metabolite form

What are the main assumptions of the One Compartment Model?

1. Body is a single process 2. Drug distribution is instantaneous 3. Equilibrium exists between blood and tissues 4. Instantaneous and well-mixed

What are the main assumptions of the Multi Compartment Model?

1. Drug distribution is instantaneous in compartments but between them they may not be the same 2. Drug distribution is not instantaneous

Half Life Concentration of Drugs

t(1/2) = 0.693/k

What happens to the half life of the drug if the clearance is decreased by 50%?

T1/2 is Doubled

How long will it take for a drug to reach one-fourth of its present concentration?

2 Half Lives