kenitiks n dynamiks Flashcards
how the drug affects the body
Pharmacodynamics
how the body acts on the drug
Pharmacokinetics
Is the study of the interactions between the chemical components of living systems and the foreign chemicals, including drugs that enter those systems.
PHARMACODYNAMICS
Drugs usually work in one of four ways:
- To replace or act as substitutes for missing chemicals
- To increase or stimulate certain cellular activities
- To depress or slow cellular activities
- To interfere with functioning of foreign cells, such as invading microorganisms or neoplasms leading to cell death (drugs that act in this way are called chemotherapeutic agents)
Drugs act in different ways to achieve results:
a. Agonists
b. Inhibitors
c. Competitive antagonist
d. Non competitive antagonist
Interact directly with receptor sites to cause the same activity that natural chemicals would cause at that site
a. Agonists
Prevent breakdown of natural chemicals that are stimulating the receptor site
b. Inhibitors
React with receptor sites to block normal stimulation, producing no effect
c. Competitive antagonist
React with specific receptor sites on a cell and by reacting there prevent the reaction of another chemical with a different receptor site on that cell
d. Non competitive antagonist
Molecules of drug A react with specific receptor sites on cells of effector organs and change the cells’ activity
Agonist interaction with receptor site on cell.
Drug A and drug C have an affinity for the same receptor sites and compete for these sites; drug C has a greater affinity, occupies more of the sites, and antagonizes drug A
B. Competitive antagonism
Drug D reacts with a receptor site that is different from the receptor site for drug A but still somehow prevents drug A from binding with its receptor sites.
C. Noncompetitive antagonism.
The ability of a drug to attack only those systems found in foreign cells
Selective Toxicity
involves the study of absorption, distribution, metabolism (biotransformation), and excretion of drugs
PHARMACOKINETICS
- In clinical practice, pharmacokinetic considerations include
-the onset of drug action ,
-drug half life,
-timing of the peak effect
- duration of drug effects - metabolism or biotransformation of the drug,
-site of excretion
The amount of drug that is needed to cause a therapeutic effect
Critical Concentration
A higher dose than that usually used for treatment to reach critical concentration quickly
Loading Dose
Dynamic Equilibrium
Processes:
- Absorption from the site of entry
- Distribution to the active site
- Biotransformation (metabolism) in the liver
- Excretion from the body
Refers to what happens to a drug from the time it is introduced to the body until it reaches the circulating fluids and tissues
ABSORPTION
Process of Absorption
-Passive diffusion
-Active Transport
-Filtration
- Major process through which drugs are absorbed into the body
- Occurs across a concentration gradient
- Movement from an area of greater concentration to lower concentration
Passive diffusion
- Process that uses energy to actively move a molecule across a cell membrane
Active Transport
- Involves movement through pores in the cell membrane either down a concentration gradient or as a result of the pull of plasmaproteins
Filtration
Involves the movement of a drug to the body’s tissues
DISTRIBUTION
Factors that affect drug distribution:
- Drug’s lipid solubility and ionization
- Perfusion of the reactive tissue
Most drugs are bound to some extent to proteins in the blood
to be carried to the circulation.
Protein Binding
Some drugs compete with each other for
protein binding sites, altering effectiveness or causing toxicity
when two drugs are given together.
Protein Binding
Is a protective system of cellular activity that keeps
many things away from the CNS
Blood Brain Barrier
Many drugs pass through the
placenta and affect the
developing fetus in pregnant
women.
Placenta and Breast Milk
The process by which drugs are changed
into new, less active chemicals.
METABOLISM (BIOTRANSFORMATION)
