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Pharmacology
UNECOM
56
Medical
Graduate
04/03/2009

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Term
Enteral absorption
Definition
administration of drug into the alimentary tract
Term
Parenteral absorption
Definition
injection of drug into skin, muscle, or blood
Term
Factors (chemical variable) affecting drug absorption
Definition
Chemical structure, molecular weight, solubility, lipid solubility
Term
Factors (physiological variable) affecting drug absorption
Definition
Gastric motility, pH at absorption site, surface area at absorption site, blood flow, presence or absence of food
Term
Fick's Law of Diffusion
Definition
Flux (molecules/unit of time)= (deltaC x A x Perm. coefficient)/Thickness
Term
Henderson-Hasselbalch Equation
Definition
pH=pKa-log(acid/base)
Term
Drug trapping
Definition
pH of bodily compartment similar to pH of unionized form of drug
Term
Factors affecting bioavailability
Definition
1. drug metabolism by enzymes in the blood
2. binding to blood proteins
Term
Biotransformation
Definition
2 phase process that modifies the chemical structure of compounds, generally to inactivate and make more water-soluble.
Term
Phase I of biotransformation
Definition
chemical reactions that change molecule, can be oxidation, reduction, or hydrolysis.
Term
Phase II of biotransformation
Definition
addition of another molecule to modified drug, via conjugation.
Term
Urine pH affect on drug excretion
Definition
weak acids excreted more readily in alkaline urine; weak bases excreted more readily in acidic urine
Term
Volume of distribution
Definition
relates the amount of drug in the body to the concentration of the drug in the blood or plasma
Vd= amount of drug in body/ concentration of drug in blood
Term
Clearance
Definition
factor that predicts the rate of elimination in relation to the drug concentration
CL= rate of elimination/ concentration of drug
Term
First-order elimination
Definition
Clearance is constant over the concentration range encountered in clinical settings
Rate of elimination= CL x concentration
Term
Capacoty-limited elimination
Definition
CL=(Vmax x C)/(Km + C)
when C>>Km, elimination rate becomes independent of drug concentrations
Term
Flow-limited elimination
Definition
elimination of drug depends primarily on the rate of drug delivery to the organ
Term
Half-life
Definition
t1/2=0.7 x Vd/CL
Term
Extraction
Definition
the effect of first-pass hepatic elimination on bioavailability is expressed as the extraction ratio
ER=CLliver/Q, where Q=hepatic blood flow
Term
Systemic bioavailability of drug equation
Definition
F (systemic bioavail.)= f (extent of absorption) x (1-ER) (extraction ratio)
Term
Dosing rate
Definition
at a steady state, the dosing rate must equal the rate of elimination
DR=RE=CL x TC (target concentration)
Term
Maintenance dose
Definition
when giving intermittent doses, the maintenance dose is calculated
MD=dosing rate x dosing interval
Term
Dosing rate w/less than 100% bioavailability
Definition
DR=Dosing rate/Foral
Term
Loading dose
Definition
When using maintenance dosing, it may take 4-5 half-lives to reach steady-state, thus a fast onset can be achieved via loading
Loadin dose=Vd x TC
Term
Cytochrome P-450 system
Definition
important in controlling phase I reactions, particularly oxidation, enzymes especially abundant in liver
Term
The Big Four of Pharmacokinetics
Definition
A-D-M-E
Absorption
Distribution
Metabolism
Excretion
Term
Pediatric absorption differences
Definition
less muscle mass may impact absorption
GI function
irregular peristalsis and changes in bile production may lead to unpredictable absorption
Term
Pediatric distribution differences
Definition
neonates can have up to 85% of total weight be water
lipid content can be greatly decreased in preterm neonate
protein binding may be diminished in neonates
Term
Pediatric metabolism differences
Definition
cytochrome P450 can be decreased in early life
Term
Pediatric excretion differences
Definition
GFR can be markedly lower in preterm and neonates
Term
Drugs targeting opiod receptors
Definition
morphine, naloxone
Term
Drugs targeting B receptors
Definition
albuterol, metoprolol
Term
Drugs targeting estrogen receptors
Definition
ethinyl estradiol, tamoxifen
Term
Drugs targeting voltage-gated Na+ channels
Definition
lidocaine
Term
Drugs targeting acetylcholinesterase
Definition
neostigmine, organophosphates
Term
Drugs targeting cyclooxygenase
Definition
aspirin
Term
Drugs targeting catecholamine reuptake
Definition
cocaine
Term
Alpha part of heterotrimeric G receptor
Definition
Involved in inhibition of adenylate cyclase
Term
Quantal dose response curve
Definition
Shows how many of a given population respond to a drug at a certain dose to elicit a certain response
Term
Concentration response curve
Definition
shows concentration (x) vs. effect/maximum effect (E/Em) (y)
Term
Efficacy
Definition
defined by the therapeutic effect that is sought, and is graphed as a y-axis
Term
Potency
Definition
amount of drug needed to garner a desired effect
Term
Therapeutic index
Definition
ratio of the dose of the drug lethal to 50% of the population to the dose of the drug therapeutically effective to 50% of the population
Term
Graded response curve
Definition
shows effect in relation to dose, for individual patient
Term
Additive effect
Definition
Drug A + Drug B= effect A + effect B
PREDICTABLE!
Term
Synergistic effect
Definition
Drug A + Drug B= effect A2 + effect B2
UNPREDICTABLE!
Term
Competitive antagonism
Definition
requires that agonist can be overcome
Term
Tolerance
Definition
decreased effectiveness of a drug that results from repeated drug exposure
Term
Metabolic tolerance
Definition
enzyme inducement following repeat exposure
Term
Pharmacodynamic tolerance
Definition
repeated administration of a drug produces changes to drug receptors and second messenger systems (affects drugs effect on body)
Term
Pharmacodynamic tolerance
Definition
repeated administration of a drug produces changes to drug receptors and second messenger systems (affects drugs effect on body)
Term
Behavioral tolerance
Definition
development of tolerance can be influenced by learning and conditioning processes
Term
Tachyphylaxis
Definition
A rapidly decreasing response to a drug following administration of the first dose
Term
Effect of St. John's Wort on CYP450-3A4
Definition
CYP450-3A4 is a major liver enzyme, and SJW decreases serum concentration of some other important drugs via this enzyme
Term
Lecithin
Definition
Most popular herbal among all age groups and sexes, use to decrease cardiovascular disease risk
Term
Sensitization or Reverse tolerance
Definition
Continuing to take a drug leads to an increased effect
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