PRACTICE QUESTIONS // EXPERT-CRAFTED LEARNING MATERIAL
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Absorption factors - THE CORRECT ANSWER -· Gastrointestinal pH
changes
· Gastric emptying
· Gastric/intestinal enzymes
· Bile acids & biliary function
· Gastrointestinal flora (type and quantity of bacteria)
· Food & nutrient interactions (most common interaction
influencing GI drug absorption)
· Lipid solubility of the drug
Distribution factors - THE CORRECT ANSWER -· Membrane
permeability: Cross membranes to site of action
· Blood brain barrier reduces the speed of drug passage into and
out of brain tissue
· Plasma protein binding: drugs bound to plasma proteins do
not cross membranes (Note: Malnutrition = âalbumin = á free
drug = greater pharmacologic response)
· Aging cause a reduction in production of plasma proteins
· Lipophilicity of drug: lipophilic drugs concentrate in adipose
tissue; remain in the body for a longer period of time
Volume of distribution - THE CORRECT ANSWER -· Body
Composition
,- Increased Total body water and extracellular fluid
-Decreased Adipose tissue and skeletal muscle
· Protein Binding (changes with aging)
-Albumin, bilirubin, a1-acid glycoprotein
-Albumin affected by nutrition
-Low albumin (hypoalbuminemia) can cause less proteinbound
drug reaching the tissue site of action.
· Tissue Binding
- Compositional changes
Metabolism factors - THE CORRECT ANSWER -o Drugs can
undergo metabolism in the lungs, blood, liver, intestines and
kidney o Volatile drugs are primarily excreted by the lungs
· The body changes drugs to more or less active forms
(metabolites), increases water solubility to increase elimination.
Phase 1 Metabolism - THE CORRECT ANSWER -· Cytochrome P450
system
· Located within the endoplasmic reticulum of hepatocytes.
· Through electron transport chain, a drug bound to the
CYP450 system undergoes oxidation or reduction.
· Drug metabolism in the liver is also affected by:
-Enzyme induction
- Drug interactions
CYP450 - THE CORRECT ANSWER -· CYP: a set of isozymes
primarily found in the liver and GI tract
,· Convert lipophilic drugs into more polar (and soluble)
molecules
· Considerable genetic variability exists across race and gender
· Results in CYP450 polymorphisms which have a direct effect
on drug metabolism.
Four isozymes are responsible for the majority of Phase I
Metabolism reactions - THE CORRECT ANSWER -1. CYP3A4/5
2. CYP2D6
3. CYP2C8/9
4. CYP1A2
If you have a patient experiencing a pharmacokinetic drug
interaction, consider...... - THE CORRECT ANSWER -CYP450.
· Some drugs or exogenous substances can induce CYP
isozymes (less effect). Example.... - THE CORRECT ANSWER -St.
John's wort (CYP3A4) and hormonal birth control
CYP450-related drug interactions can make predicting blood
plasma levels/steady state levels difficult.
Example.... - THE CORRECT ANSWER -If a drug inhibits enzymatic
activity, a substrate drug for that enzyme system will have a
greater concentration in the blood.
If a drug inhibits CYP isozymes, what is the effect of the
substrate drug - THE CORRECT ANSWER -The substrate drug will
have greater effect
, Phase 2 Metabolism - THE CORRECT ANSWER -· Polar group is
conjugated to the drug
· Results in increased polarity of the drug
Types of phase 2 metabolism reactions - THE CORRECT ANSWER --
Glycine conjugation
-Glucuronide conjugation
-Sulfate conjugation
What is competitive antagonism? - THE CORRECT ANSWER -where
one drug displaces another on cell receptors.
How is metabolism effected by different ethnic groups? - THE
CORRECT ANSWER -Different ethnic groups may have different
hepatic metabolism rates
Routes of elimination - THE CORRECT ANSWER -1. Pulmonary =
expired in the air (volatile substances)
2. Bile = excreted in feces 3.
Renal
-glomerular filtration
- tubular reabsorption
- tubular secretion
Glomerular filtration rate (GFR) (Normal) - THE CORRECT
ANSWER90-125L/min