Pharmacokinetics: Key Terms & Definitions for Medicine

Major processes

-absorption

-distribution

-elimination (metabolism/excretion)

Application of pharmacokinetic data and a few simple formulas make it possible to calculate______ and _______doses

-loading

-maintenance

Routes of administration

-enteral

-parenteral

enteral

-oral

-rectal

-inhalation

parenteral

-injection

-topical/transdermal

Movement across cell membranes can be done via

-passive diffusion

-active transport

-facilitated diffusion

-endocytosis

first pass effect

-drug absorbed into alimentary canal

-transported to liver thru portal circulation

-results in sig amt of drug being metabolized or destroyed

-orally administered drugs must have a sufficient dose left over to be effective

-not all drugs undergo this effect

absorption

-a pH dependent process

bioavailability

-how much of drug is available after absorption and circulation

-measured as fraction of administered dose that reaches systemic circulation

Bioavailability based on routes of administration

-IV: 100%-fastest

-intramuscular: 75-less than/equal to 100%-large volumes, may be painful

-sub-Q: 75-less than/equal to 100%-smaller vol than IM, may be painful

-Oral: 5-100%-most convenient, first pass effect may be significant

-rectal: 30-<100%-less first pass effect than oral

-inhalation: 5-<100%-often very rapid onset

-transdermal: 80-less than/equal to 100%-usually slow absorption, used for lack of first pass, prolonged duration of action

Distribution

-how uniformly present is the drug throughout the body

What does distribution depend on?

-tissue permeability

-blood flow

-binding to plasma proteins

-binding to subcellular components

Volume of distribution (EXAM Q)

-amt of drug administered divided by concentration of drug in plasma

-compared to avg total body fluid of 70kg man

-closer to 42 L is more uniform distrib outside blood

-farther away from 42 L is more sequestered within blood

Drugs are excreted either ________ or __________

-untransformed

-as a metabolite (after undergoing conjugation, hydrolysis, oxidation, reduction)

Clearance

-function of perfusion, concentation of a drug entering an organ, and concentration of drug leaving the organ

-L/min

half-life

-amt of time necessary for 50% of drug remaining in the body to be eliminated

-depends on volume of distribution and clearance

Duration of action

-length of time drug effectively interacts with target

-affected by distribution, metabolism and elimination

-may be prolonged despite drug being eliminated

Variations in drug response and metabolism depend on

-genetics

-disease

-enzyme induction

-drug-drug interactions

-age

-diet

-sex

-other factors