Chapter 1: Principles of Pharmacology Flashcards
What are the pharmacokinetic factors?
- Routes of administration
- Absorption and distribution
- Binding
- Inactivation resulting from metabolic processes that influence the intensity and duration of drug effects
- Excretion through urine or feces by way of the lives or kidneys
What is pharmacokinetics?
The factors beyond the chemical structure of a drug that determine its action and bioavailability. It is essentially how the organism affects the drug.
What are lipid-soluble drugs?
Lipid-soluble drugs can pass through the phospholipid bilayer of cell membranes. Movement goes from the side of the membrane with the highest concentration to the side with the lowest concentration and the bigger the difference the faster the diffusion across the membrane.
What are ionized drugs?
Drugs that are not lipid-soluble beause they are weak acids or bases that become ionized when dissolved in water.
What is the blood-brain barrier?
Cerebrospinal fluid (CSF) separates the blood from the brain capillaries. The blood-brain barrier is selectively permeable; lipid-soluble molecules can pass through by diffusion and ionized molecules can pass through carrier-mediated transport (which is limited). Drugs that can pass the barrier diffuse into the brain and enter the central nervous system while drugs that cannot circulate through the blood and act peripherally on the rest of the body.
Define “half-life.”
Half-life refers to the amount of time it takes for 50% of a drug to be removed from the blood. Drug clearance, or how long it takes for the drug to be eliminated from the body, is exponential and typically measured in half-lives.
What is meant by the term “pharmacodynamics”?
Pharmacodynamics refers to the physiological and biochemical interaction between the drug molecules and target tissue. It is concerned with the effects that drugs have, including side effects. Pharmacodynamics is essentially the study of how the drug affects the organism.
What are receptors?
Receptors are the initial sites of action of biologically active agents (i.e. ligands). They are large protein molecules either located on the surface of the cell or within the cell.
What are ligands?
Ligands are molecules that bind to receptors with some selectivity. Examples of ligands include neurotransmitters, hormones and drugs). When ligands bind to receptors, they can initiate changes in an effector and cause intracellular changes.
What is up-regulation?
When the number of receptors increases following chronic use of receptor antagonists (blocker) or from denervation.
What is down-regulation?
When the number of receptors decrease following chronic use of receptor agonists (activation).
What is tolerance?
Tolerance described a diminished response after repeated exposure to a drug. A higher dose of the drug becomes necessary in order to produce the same magnitude or effect as the original dose. Tolerance can be metabolic, pharmacodynamic or behavioural.
What is metabolic tolerance?
Metabolic tolerance is when repeatedly using the drug reduces the amount available at the target tissue, for example, when the drug increases its own rate of metabolism.
What is pharmacodynamic tolerance?
Pharmacodynamic tolerance is when there are compensatory changes in nerve cell function as a result of the continued presence of the drug.
What is behavioural tolerance?
Behavioural tolerance involves learning and adaptation where tolerance occurs in the environment in which the drug was repeatedly administered but not in new environments.
