[6] Pharmacokinetics Flashcards
Definition: Pharmacokinetics
Effect of the body on the drugs
kinEtics : admE (Absorption, Distribution, Metabolism, Excretion)
Routes of Administration
Enteral
Parenteral
Examples of Enteral Administration
Oral
NGT
Gastrostomy Tube
Examples of Parenteral Administration
Intravenous Intramuscular Subcutaneous Intradermal Topical
[Better or Worse Arbsorption]
Non-Ionized
Better
[Better or Worse Arbsorption]
Small Molecules
Better
[Better or Worse Arbsorption]
Lipid-Soluble
Better
[Better or Worse Arbsorption]
Ionized
Worse
[Better or Worse Arbsorption]
Large Molecules
Worse
Dopamine and Serotonin penetrate brain tissue poorly, however these precursors enter with relative ease.
L-Dopamine
5-Hydroxytryptophan
Used to treat Parkinson’s Disease
L-Dopa
Define: Volume of Definition
Hypothetical Volume
Not the same as PV, BV, Interstitial Volume, Intracellular Volume, Extracellular Volume
Formula: Volume of Distribution
Dose Administered / Concentration
[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
X
Define: Phase I Reactions
Functionalization Reactions
Oxidation, Reduction, and Hydrolytic Reactions
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?
- Body is a single process
- Drug distribution is instantaneous
- Equilibrium exists between blood and tissues
- Instantaneous and well-mixed
What are the main assumptions of the Multi Compartment Model?
- Drug distribution is instantaneous in compartments but between them they may not be the same
- 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
