chapter 2 Flashcards
absorption
what happens to a drug from the time it enters the body until it enters the circulating fluid
active transport
mvmt of substances across a cell membrane against the concentration gradient; this process requires the use of energy and important for drug excretion in the kidney
chemotherapeutic agents
synthetic chemicals used to interfere w/ the functioning of foreign cell populations; frequently used to refer to drug therapy of neoplasms, but also any drug therapy affecting any foreign cell
critical concentration
the concentration a drug must reach in the tissues that respond to the particular drug to cause the desired therapeutic effect
distribution
mvmt of a drug to body tissues; the places where a drug may be distributed depend on the drug’s solubility, perfusion of the area, cardiac output, and binding of the drug to plasma proteins.
enzyme induction
process by which the presence of a chemical that is biotransformed by a particular enzyme system in the liver causes increased activity of that enzyme system
excretion
removal of a drug from the body; primarily occurs in the kidneys, but can occur thru the skin, lungs, bile or feces
first-pass effect
a phenomenon in which drugs given orally are carried directly to the liver after absorption, where they may be largely inactivated by liver enzymes before they can enter the general circulation; oral drugs are often given in higher doses b/c of this early breakdown
glomerular filtration
the passage of water and water-soluble components from the plasma into the renal tubule
half-life
the time it takes for the amount of drug in the body to decrease to one half of the peak level it previously achieved
hepatic microsomal system
liver enzymes tightly packed together in the hepatic intracelluar structure, responsible for the biotransformation of chemicals, including drugs
loading dose
use of a higher dose than what is usually used for Tx to allow the drug to reach the critical concentration sooner (high dose initially if there is a prolonged period to reach critical concentration and need action now) (*pharmacokinetics)
passive diffusion
mvmt of substances across semipermeable membrane w/ the concentration gradient; this process does not require energy; is the major process of dug absorption into the body
pharmacodynamics
HOW THE DRUG AFFECTS THE BODY.
the study of the interactions b/w the chemical components of living systems and the foreign chemicals, including drugs, that enter living organisms; the way a drug affects the body
pharmacogenomics
the study of genetically determined variations int eh response to drugs
pharmacokinetics
HOW THE BODY ACTS ON THE DRUG.
the way the body deals w/ a drug, including absorption, distribution, biotransformation, and excretion
placebo effect
documented effect of the mind on drug therapy; if a person perceives that a drug will be effective, the drug is much more likely to actually be effective
receptor sites
specific areas on cell membranes that react w/ certain chemicals to cause an effect w/in the cell
selective toxicity
property of a chemotherapeutic agent that affects only systems found in foreign cells w/o affecting healthy human cells (e.g. specific antibiotics can affect certain proteins or enzyme systems used by bacteria but not by human cells) Ex. Penicillin
In what 4 ways do drugs work?
- replace or substitute missing chemicals, 2. increase/stimulate certain cellular activities, 3. Depress/slow cellular activities, 4. interfere w/ function of foreign cells
How do drugs act on the cell membranes?
They fit in receptor sites where certain chemicals cause an effect w/in the cell. Nearby enzymes break down the reacting chemicals and open the receptor site for further stimulation. (*pharmacodynamics)
Agonist drugs
Drugs that interact directly w/ receptor sties to cause the same activity that natural chemicals would cause at that site. (*pharmacodynamics)
What do monoamine oxidase (MAO) inhibitors block?
The breakdown of NE by the enzyme MAO, which allows prolonged effects that can be therapeutic (relieving depression) or adverse (incr HR). (Normally MAO breaks down NE, removes it from the receptor site, and recycles the components to form new NE.) (*pharmacodynamics)
Competitive antagonists
drugs that react w/ receptor sites to block normal stimulation, producing no effect. (Ex. curare occupies receptor sites for acetylcholine (ACh)) (*pharmacodynamics)
Noncompetitive antagonists
Drugs that react w/ specific receptor sites on a cell, by reacting there it prevents the reaction of another chemical w/ a different receptor site on that cell. (*pharmacodynamics)
In what 4 ways does the body deal with drugs?
Absorption, distribution, metabolism (biotransformation), and excretion (*pharmacokinetics)
How much of a drug is needed to cause a therapeutic effect?
It should maintain the critical concentration. Too much of a drug will produce toxic (poisonous) effects, and too little will not produce the desired therapeutic effects.
Pharmacokinetics is how the body acts on the drug. What is considered in the clinical setting ?
Onset of drug action, drug half-life, timing of the peak effect, duration of drug effects, metabolism of drug and site of excretion.
Dynamic equilibrium
The actual concentration that a drug reaches in the body resulting from absorption, distribution, metabolism and excretion.
Where in the body can drugs be absorbed?
GI TRACT: oral or rectal (oral is less invasive, cheaper and most often used in clinical practice)
VEIN: IV administration causes the drug to directly enter the circulating blood, bypassing many complications of absorption from other routes
How are most drugs distributed?
Most drugs are bound to some extent to proteins in the blood to be carried into circulation. The protein–drug complex is relatively large and must be freed from the protein’s binding site at the tissues.Some drugs are tightly bound and are released very
slowly. These drugs have a very long duration of action because they are not free to be broken down or excreted.
What kind of drugs are not able to pass the blood-brain barrier?
Lipid soluble. Cross the BBB affects the CNS. This is clinically significant in treating a brain infection w/ antibiotics. Almost all antibiotics are not lipid soluble and cannot cross the blood–brain barrier.
Which organ is the most important in drug breakdown in the body?
The liver. The breakdown helps prevent adverse reactions in the body.
Why is the recommended dose for oral drugs higher than parenteral drugs?
b/c of the first-pass effect. a large percentage never reaches the tissues b/c of the breakdown in the liver
Which organ has the most important role in excretion of medication?
The kidney. Other routes of excretion are the skin, saliva, lungs, bile, and feces.
How is half-life affected? What does it effect clinically?
Absorption, distribution, metabolism, excretion
Dosing schedules.
What factors influence drug effects?
Weight, age, gender, allergies, diseases, patient attitude, environmental, drug tolerance, drug interactions (see pg 26)
What weight do most drug recommendation target?
150-pound person. So a heavier person may require more and a smaller person may require less.
Why is age a factor in influence of drug effects?
b/c children metabolize many drugs differently than adults do
Why is gender a factor in influence of drug effects?
Men have more vascular muscles and IM injections have faster effects. Women have more fat so drugs that deposit there are more slowly released.
What type effects can occur w/ Drug-to-Drug Interactions?
can occur any time 2 or more drugs are taken together.
ANTAGONISTIC: 2 drugs cancel each other out
ADDITIVE: 2 drugs w/ similar mechanisms increase the effects
SYNERGISTIC: 2 drugs w/ different mechanisms have greater effect together
Why are drugs best taken on an empty stomach? When are they not?
B/c of drug-food interaction. Vitamin K and dairy can cancel the drug’s effect or render ineffective.
*there are some that irritate the GI tract and need food
