Pharmacokinetics Flashcards
(45 cards)
what is the definition of pharmacokinetics?
a study of how the drug moves throughout the body
what dictates a drugs activity at the receptor site and why?
certain enantiomers have higher affinity
what is an example of medication that contains both L and D isomers?
amphetamines given as ‘mixed salts’
for patients with hypothyroidism what isomer of thyroid hormone is given?
L-isomer
what is captopril used for and what is its trade name?
- ACE inhibitor used in treatments for hypertension
- Capoten
what does ADME stand for and what can influence them ?
- Absorption
- Distribution
- Metabolism
- Excretion
age, ethnicity and disease state
how is absorption influenced?
route of administration and how it distributes within the body
what are the two routes a drug may be administered and what are examples?
enteral
- mouth (50% bypass first-pass effect)
- rectal (100% bypass first-pass effect)
- sublingual
parenteral (bypass first-pass effect)
- intravenous
- intramuscular
- subcutaneous
- transdermal
what does extensive first-pass effects mean?
- drugs taken orally will deposite into the hepatic portal system
what is the quickest way to make 100% bioavailability ?
IV
what factors influence absorption?
- Concentration of drug given
- route of administration
- Surface area of the cell membrane
- Lipophilicity
- Lower the thickness of the membrane, the greater the absorption
- Lower the molecular weight of the drug the greater the absorption
- The greater the regional blood flow to the target tissue, the greater the absorption.
- drugs given orally, the rate of gastric emptying is important
what determines the hydrophobicity or hydrophilicity of a drug?
partition coefficient
what is Fick’s Principle equation?
Diffusion = (C1-C2) X Surface area of membrane X Permeability Coefficient/
Thickness of membrane
how does passive vs active transport effect the rate of absorption?
any drug that uses a transporter (active) will have a cap of effectiveness even if the dose is increased
what are the 4 processes that absorption can perform?
- aqueous diffusion
- passive diffusion
- carrier mediated
- active transport
what drugs can cross the placenta? what are some examples?
Nonionized drugs and drugs with high lipophilicity typically will have a higher advantage in crossing the placenta
- opioids
- benzodiazepines
- atropine
- beta-blockers
- local anesthetics
what are two important mechanisms for receptor cycling and release of neurotransmitters?
- exocytosis
- endocytosis
the absorption of weak acids and weak bases are influenced by?
ionization state
what are the normal pH’s of the stomach, small intestines and colon and how does the pH effect absorption?
- 2-2.5
- 6-8
- 5.5-7
drugs where their pKa is closest to the pH absorb better
what is an effective way to eliminate weak bases through the kidneys ?
ion trapping
explain what ion trapping is?
ion trapping occurs when a drug becomes ionized in a specific environment, preventing it from crossing membranes and leading to its accumulation in that compartment.
what is bioavailability and what factors influence it?
-the fraction (f) of unchanged drug reaching the systemic circulation following administration by any route
* Foods or certain types of drugs can influence the bioavailability.
what can influence drug distribution to various parts of the body?
plasma proteins such as albumin and alpha-1-glycoprotein
what does Volume Distribution tell us and what is the formula?
- what compartment the drug enters
- VD = Amount of Drug in the body / PC
PC = plasma concentration in the body