basic concepts and processes Flashcards
name some different functions cells carry out
- take in raw materials
- manufacture products required to maintain bodily functions
- deliver those manufactured products to the appropriate destination within the body
- differ from one tissue to another
- exchange materials with immediate environment
- obtain energy from nutrients
- reproduce
- communicate with one another via biologic chemicals
True or False?
while all cells differ from one tissue to another, they share certain common characteristics
True
rationale: while all cells differ from one tissue to another, they share common characteristics, including the ability to exchange materials from their immediate environment, obtain energy and nutrients, synthesize complex molecules, reproduce, and communicate with one another via biologic channels
drugs must interact with cell membrane to affect…
cellular function
most drugs are given for ______ effect (most often occurs at a cellular level)
systemic
what moves drug molecules through the body
transport pathways and mechanisms
what are the three main pathways of drug movement across cell membranes?
- direct penetration of the membrane by lipid soluble drugs (most common)
- passage through protein channels
- carrier proteins
describe direct penetration of the membrane by lipid soluble drugs
- lipid soluble drugs dissolve in the lipid layer of the cell membrane and diffuse into or out of the cell
- most systemic drugs are formulated to be lipid soluble
- most common pathway
describe passage through protein channels
- gated channels regulate the movement of ions
- only a few drugs are able to use this pathway because most drug molecules are too large to pass through
describe using carrier proteins as a pathway into the cell
- carrier proteins attach to the drug molecules and move them across cell membranes
- all carrier proteins are selective in the substances they transport; a drugs chemical structure determines which carrier will transport it
describe pharmacodynamics
- effect the drug has on the body
- reactions between living systems and drug/drug actions on target cells and the resulting alterations in cellular biochemical reactions and functions
what are the four ways drugs primarily work
- 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 the functioning of foreign cells leading to cell death (chemotherapeutic drugs)
describe the receptor theory of drug action
drugs exert their effects by chemically binding with receptor cells through…
- activation, inactivation, or alteration of intracellular enzymes
- changes in the permeability of cell membranes to one or more ions
- modification of the synthesis, release, or inactivation of neurohormones
describe receptors
specialized protein structures that are found on cell membranes
drugs designed to target specific types of receptors to initiate, limit, or prevent a ________
biologic response
with receptors, response to a drug will depend on…
the affinity or attraction to a receptor and the concentration of the drug already at the receptor site
describe agonist
drugs that produce or prolong activity
describe antagonists
- drugs that block a response
- can be competitive for the receptor site
relatively few drugs do not act on receptor sites. drugs in the following classes apply…
- antacids
- osmotic diuretics
- several anticancer drugs
- metal chelating agents
describe nonspecific drug effect
- selective to certain receptors but those receptors may be in different organs or tissues (ex. cholinergic receptors)
- produce response wherever a particular type of receptor exists
describe an example of nonspecific drug effect
- bethanechol
- cholinergic receptor sites in heart, blood vessels, stomach, bronchus, and eye
- response include decreased HR, decreased BP, increased gastric secretion, constricted bronchioles, and constricted pupils
describe nonselective drug effect
not selective to just one type of receptor, it can act on different receptors throughout the body
describe an example of nonselective drug effect
- epinephrine affects receptors Alpha 1, Beta 1, and Beta 2
- Alpha 1 receptors are found in blood vessels, causes an increase in BP
- Beta 1 receptors are found in the heart, causes and increase in HR
- Beta 2 receptors are found in the bronchus, causes relaxed bronchioles
describe pharmacokinetics
drug movement through the body to reach sites of action, metabolism and excretion
what are some specific processes of pharmacokinetics
absorption, distribution, metabolism (biotransformation), and excretion
describe absorption
- process that occurs from the time a drug enters the body to the time it enters the blood stream to be circulated to tissues
- process: active and passive transport
describe active transport
- molecule move across a membrane from an area of low concentration to an area of high concentration
- takes energy
describe passive transport
- movement across a membrane from area of high concentration to an area of low concentration
- no need for energy
absorption
onset of drug action is determined by…
the rate and extent of drug absorption
what factors affect rate and extent of drug absorption
- dosage, form, route of administration
- administration site blood flow, GI function (gastric pH)
- the presence of food or other drugs
absorption of enteral medication includes…
meds given by mouth or any GI tubes
absorption of enteral medications can be altered by…
- GI motility
- presence of food in stomach
- pH of stomach
- amount of bowel surface area
- can be influence by pain, stress that could divert blood flow from GI/stomach
which is faster?
enteral or parenteral absorption?
parenteral
describe absorption of parenteral (outside of GI tract) drugs
includes routes such as IV, IM, and Sub Q
how can absorptions of parenteral drugs be altered
- altered blood flow to area (think about temp and vascular issues)
- altered by tissue type (fat or muscle) (this is important with Sub Q or IM med injection)
- muscle tissue has more blood vessels, so absorption is faster
- Sub Q tissue (fatty) has less blood vessels so absorption is slower
- IV administration is not affected by absorption “rules” since the drug is immediately administered into the bloodstream/circulation
rank the ways of absorption from fastest to slowest
- IV
- IM
- Sub Q
- enteral
describe distribution
- the transportation of drug molecules within the body
- drugs are carried by blood and tissues fluids to action sites/metabolism sites/excretion sites
- depends on adequacy of blood circulation
distribution process can be affected by
- protein binding
- when drug is bound to protein it is inactive, unbound drug is free, active drug
- only unbound drug to able to move through capillaries
describe protein binding
- drugs attach to protein molecules and travel to site of action (mostly bind to albumin)
- allows for part of the drug to be stored as needed and can be distributed over time
describe why medications with low or loose protein binding capacity are going to have less duration of action
because they will be released faster in the bloodstream, there will not be a lot of binding to keep the drug around in the system
describe how protein bound drugs are dosed to keep the body at normal levels
when bloodstream level of the drug goes down because the active (unbound) drug is excreted, the inactive (bound) drug is then released from the protein (albumin) and the drug stays in the blood
why could a patient with hypoalbuminemia experience toxicity from excessive free drug in the body
little to no albumin for drug to bind to, it is important they are monitored for the excessive free drug
where else can drugs be stored in the body (other than the bloodstream)
- muscle, fat, and other tissues. drug is release as plasma drug levels go down in the blood
- drugs that are stored extensively in other tissues have a long duration of action
describe the blood-brain barrier
- the blood-brain barrier is composed of capillaries with tight bonds in the CNS
- these capillaries limits the passage of most ions and large molecular weight compounds (including some drugs) from the blood to the brain
- to pass the blood-brain barrier, medications must be highly lipid soluble
describe some considerations to take with drug distribution during pregnancy and lactation
- most drugs cross the placenta and may affect the fetus
- many drugs enter breast milk and may affect nursing infant