Exam 1, Ch. 3 review Flashcards
List the pharmacokinetic variables (ADME)
Absorption, Distribution, Metabolism, excretion
Describe the four ways a drug gets across barriers.
Aqueous diffusion, Lipid diffusion, Special carriers, Endocytosis and exocytosis
Define Volume of distribution (Vd)
Space available in body to contain drug
Define Clearance (CL)
Ability of body to eliminate drug (NOT elimination)
- Predicts ROE
Clearance and ROE - First-order elimination
Most drugs, clearance is CONSTANT, ROE varies.
Clearance and ROE - Zero order elimination
Occurs when bodys ability to eliminate a drug has reached its maximum capacity. e.g. all transporters are being used, can only clear at its maximum rate.
ROE is constant, and clearance varies with concentration.
Concentration (C)
How much of the drug is in the body?
Rate of elimination (ROE)
CL x C
-Varies with concentration
Target Concentration (TC)
Concentration that will produce desired effect
Half-life (T1/2)
Time required to change drug in body to 1/2 concentration.
Bioavailability (F)
Fraction of unchanged drug reaching systemic circulation
Relate Vd and CL to drugs (what is meant by a high Vd? a high CL?)
A high Vd means that a large portion of the drug is leaving the bloodstream and distributing into tissues, they tend to be lipophiic in nature, may accumulate in fat. This can be a longer half life and slower removal from body.
A high CL means the drug is eliminated by the body rapidly.
In total, High Vd and low CL means it will last a long time and can be a potent drug. Low Vd and low CL will require frequent dosing.
Define capacity limited elimination and the variables in the equation
Zero-order elimination, the body can only get rid of the drug so fast, its going as fast as possible and its clearance amount will be the same every hour until it gets below limited elimination.
-non-linear
-Starts as zero order, turns into 1st order once drug is cleared enough.
Analyze flow dependent elimination as it relates to extraction ratio.
Depends on blood flow through the organ.
blood flow (x) extraction ratio = organ clearance.
Q is the flow of blood.
drug into organ -> drug out of organ = What % of drug came out?
IF blood flow is low, but extraction ratio is high, what’s the clearance?
Low.
Clearance is ONLY high (normal) if both ER and blood flow is high.
Estimate the half-life of a drug based on its clearance and volume of distribution.
use the half life formula, which is 0.7 x Vd divided by CL
Describe the blood level versus time for drugs subject to zero-order elimination and for
drugs subject to first-order elimination. What remains constant (CL, or ROE)?
In first order elimination, clearance remains constant. It clears the same amount of drug every hour.. In zero-order elimination, it clears at the same ROE every hour until the concentration is low enough to move to first-order.
List 7 routes of drug administration.
IV, IM, Subcutaneous, transdermal, oral, rectal, sublingual, inhalation.
Calculate half-life, loading and maintenance dosage regimens for oral or intravenous
administration of a drug when given the following information: target concentration,
oral bioavailability, clearance, and volume of distribution.
PRACTICE QUESTIONS GIVEN! DO THEM!
Calculate the dosage adjustment required for patients who are not 70 kg
IF DRUG DOES NOT PENETRATE FAT, USE:
ideal body weight for obese people, which is:
men = 52 + (1.9kg x inches over 60in)
women = 49 + (1.7kg x inches over 60in)
Describe Therapeutic Drug Monitoring (Peak and trough).
Peak: drawn 5-10 minutes after IV drug admin
Trough: 30 minutes prior to next dose of the drug. This all helps assess individual responses in comparison to standard population.
Specifically used in digoxin and theophylline
most important thing affecting this is clearance
List the test used to determine kidney function.
Creatinine clearance. Muscles produce creatinine and kidneys clear them, telling us how well kidneys are functioning.
