Pharmacokinetics Flashcards
What relationship does pharmacokinetics describe?
dose - concentration
What relationship does pharmacodynamics describe?
concentration - effect
What is pharmacokinetics?
What the BODY does to the DRUG
What are the 4 components of pharmacokinetics?
Absorption, Distribution, Metabolism, Excretion
What is Fick’s Law of Diffusion?
Rate of Diffusion = Concentration Gradient * Surface Area * Diffusion Coefficient / Membrane Thickness
The rate of diffusion is directly proportional to what?
Concentration Gradient, Surface Area, and Diffusion Coefficient
The rate of diffusion is inversely proportional to what?
Membrane Thickness
What is bioavailability?
The fraction of unchanged drug that reaches systemic circulation aka the free drug available to a receptor
What is the equation for determining bioavailability (F)?
F = Bioavailable dose / Administered dose * 100
What is the bioavailability of medications given via the oral route?
5-100%
What is First Pass Hepatic Metabolism?
Medications are first distributed through the portal vein to the liver where they are then secreted in the bile leading to low bioavailability
What is the bioavailability of medications given via sublingual/buccal routes?
60-100%
What is the bioavailability of medications given via intranasal route?
up to 95%
What is the bioavailability of medications given via the rectal route?
30-100%
What routes of administration are subject to First Pass Hepatic Metabolism?
Oral, proximal rectal
What is the bioavailability of medications given via SQ/IM routes?
75-100%
What is the bioavailability of medications given via the IV route?
100%
What are the molecule requirements for a medication to be given transdermally?
lipid & water soluble, MW <1000, dose <10 mg over 24 hours, pH 7-9
Where do the veins in the mouth drain?
SVC
What body type has the highest percentage of BW as water?
Infants 70%
What is the volume of total body water?
42 liters
What is the volume of plasma?
4 liters
What is K12?
movement from the central to the peripheral compartment
What is K21?
movement from the peripheral to the central compartment
What drug properties affect the volume of distribution?
plasma protein binding, ionization, lipid solubility
What is the equation for the volume of distribution?
amount of drug / desired plasma concentration
Do lipid or water soluble meds require higher doses to distribute?
lipid soluble meds
What is aqueous diffusion?
driven by concentration gradient across membrane for lipid insoluble meds
What is lipid diffusion?
driven by concentration gradient across phospholipid bilayers
What is active transport?
driven by sodium pump using ATP
What is facilitated diffusion?
passive action without using ATP using special carriers
What is endocytosis?
the wall of a membrane engulfs the molecule within the cell (phago-solids, pino-liquids)
What can protein binding affect?
distribution of the drug, potency, elimination
What are the 3 main proteins for plasma protein binding?
albumin, alpha1-acidglycoprotein (AAG), beta-globulins
Does albumin bind to acidic or basic drugs?
acidic (Thiopental)
Does AAG bind to acidic or basic drugs?
basic (local anesthetics)
Factors that decrease albumin will INCREASE or DECREASE the amount of free drug.
INCREASE
Factors that increase AAG will INCREASE or DECREASE bioavailability and require a SMALLER or LARGER dose.
DECREASE, LARGER
Vd is DIRECTLY or INVERSELY proportionate to the amount of protein binding?
INVERSELY
Do polar molecules have GOOD or POOR lipid solubility?
POOR
Drugs that are more ionized are LIPID/WATER soluble and POLAR/NONPOLAR.
water-soluble and polarized
True/False: Ionized molecules have a positive or negative charge.
True
True/False: Ionized molecules readily cross membranes.
False
True/False: Ionized molecules repel cells with similar charges.
True
Ionized/Nonionized: Pharmacologically active.
nonionized
Ionized/Nonionized: Easily cross lipid barriers
nonionized
Ionized/Nonionized: Easily metabolized.
nonionized