Pharmacokinetics Flashcards
What is pharmacokinetics?
Describes how drugs are handled within the body
What are the four phases of pharmacokinetics
Absorption
Distribution
Metabolism
Excretion
Define pharmacodynamics
What’s the drug does to the body
What is the difference between pharmacokinetics and pharmacodynamics
Pharmacokinetics is what the body does to the drug and pharmacodynamics is what the drug does to the body
Define half life
the time it takes for the concentration of the drug in the plasma or the total amount in the body to be reduced by 50%
First past metabolism
It is the fraction of drug lost during the process of absorption which is generally related to the liver and gut wall.
Describe the function of drug metabolism in the liver
- To deactivate drug
- To change chemical structure sosufficiently water soluble to be excreted by urine or bile
What are the drug factors affecting the rate and extent of absorption
Molecular size, lipid solubility, ionisation at physiological pH, chemical form and pharmaceutical nature of the drug
What are the three factors affecting absorption
Physical barriers , drug factors and patient factors.
Define bioavailability
the proportion of a drug or other substance which enters the circulation when introduced into the body and so is able to have an active effect.
What amount of bioavailability does IV have when administered? 
100% Absorption 100% bioavailability
What amount of bioavailability does Intramuscular and subcutaneous injection have when administered?
100% Absorption but less than 100% bioavailability
What amount of bioavailability does Oral drugs have when administered?
Less than 100% Absorption and 0-60% bioavailability
Define passive diffusion
type of membrane transport that does not require energy to move substances across cell membranes.
Rate of passive diffusion depends on…
Lipid solubility
Molecular size
Concentration gradient
