Chapter 2 Flashcards
Pharmacokinetics
Drug movement through the body that is necessary to achieve drug action
Absorption, distribution, metabolism, and excretion
Absorption
Movement of drug into the blood stream after administration
Drugs taken by mouth
Disentigrate into small particles and then mix with a liquid (dissolution) to be absorbed by GI
Enter bloodstream following absorption across mucousal lining in small intestine. Dependent on villi
Fillers and inert substances (excipients)
Simple syrup, vegetable gums, aromatic powder, honey, elixirs
They increase the absorbality of the drug to make It a certain size
enteric coated drugs
Resist that gastric acid in stomach so It is absorbed in the small intestine
Should not be crushed
Passive transport
Diffusion and facilitated diffusion
Diffusion
High concentration to low
Facilitated diffusion
Carrier protein needed high-low
Active transport
Carrier protein low-high
Intramuscular absorption
Faster in muscles with increased blood flow
Subcutaneous generally has lower blood flow but are more rapid than by mouth
Rectal absorption
Slower than oral drugs.surface area in rectum is smaller
Absorption of oral drugs after GI
Intestinal lumen-liver-via hepatic portal vein-liver reduces amount of active drug (first pass effect)
Bioavailability
Percentage of available drug available for activity. Varies based on first-pass metabolism
Factors in bioavailability
Drug form Route Gastric mucosa and motility Administration with food and other drugs Changes in liver metabolism
Distribution
Movement of drug from circulation to body tissues
Influenced by rate of blood flow, drugs affinity to tissue, and protein binding
Protein binding
The portion of the drug that is bound to the protein is inactive because It cant interact with tissue receptors
Free drugs can exit blood vessels and reach their site of action
Highly bound protein drugs
More than 90% bound
2 highly protein-bound drugs are administered together, they compete for a binding site leading to an increase in free drugs. The higher the binding the more likely to bind.
Blood Brain Barrier
The BBB protects the brain from foreign substances. Blocks 98% of the drugs.
Drug metabolism
When the body chemically changes drugs into a form that can be excreted. LIVER.
Liver enzymes
Collectively referred to as the cytochrome P450 system, convert drugs to metabolites
Lipid soluble-water soluble substance for renal excretion. Some are transformed into active metabolites.
Drug half life
The drug half life is the time It takes for the amount of drug in the body to be reduced by half. The amount of drug administered, the amount of drug remaining in the body from previous doses, metabolism, and elimination affect the half-life of a drug.
Loading dose
A large initial dose that is significantly higher than maintenance dosing, therapeutic effects can be obtained while a steady state is reached