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NR 508 PHARM MIDTERM STUDY GUIDE (LATEST 2021) | 100% CORRECT DOCUMENT
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NR 508 PHARM MIDTERM STUDY GUIDE 2021Chapter 2: Review of Basic Principles of Pharmacology
Metabolism: Metabolism & Half Life
Metabolism can increase, decrease onset duration of action, and toxicity of
medications
Change one chemical into another
First pass metabolism: liver major organ for drug metabolism because it contains
high amounts of drug metabolism enzymes and because it is the first organ
encountered by the drug once they are absorbed by the GI tract. Determines if can
be given orally.
Rate of drug metabolism depends on drug blood level and the affinity of the drug
to be metabolize by the metabolizing enzyme.
The metabolism of the drug is related to the concentration of the drug. A fixed
fraction of the drug is metabolized per hour. First order metabolism is time drug
decreases by half (half-life). In other words, when the drug reaches half of the
concentration, then we can call it first order metabolism
50% at one half-life 75 at two half-lives and 87.5 at three half lives
Drug Responses
Before a medication can produce a response, it often must overcome homeostatic
mechanisms.
Homeostasis is when the cell or tissue does NOT respond to the drug and instead
maintains the environment by keep doing what it knows best, fix itself.
Pharmacology is the study of substances that produce biological responses,
measurement of what happens when we administer medications is important.
Receptors: agonists, antagonists
Agonists: drugs that produce receptor stimulation and change what they bind
Agonist is a chemic that binds to a receptor and activates the receptor to produce a
biological response.
, 1
Agonist causes an action in the body; The Antagonist blocks the action of the
agonist. By occupying the receptor
Agonists- you tell the body what to do
Antagonist- you tell the body what not to do by blocking the receptor thus blocking
biological response
Antagonist: occupy receptor without stimulating them prevent agonist from
occupying them.
Provides no direct response. The response we see following administrating of
antagonist results from inhibiting receptor stimulation by agonist. For example:
BB propanol and atenolol.
The effect of an antagonist is dependent on its blood levels and its affinity for the
receptor.
it is possible to overcome the antagonist effects with higher concentrations of the
competing agonist
Pharmacokinetics: Absorption, Distribution, Protein Binding, Metabolism
(including first-pass and Phase I and II)
Absorption
By weight solubility, and other factors
GI like foods change absorption
The route of administration also affects patient compliance
Enteric-coated formulations protect the medication in the stomach and only
disintegrate and dissolve when they reach the gentler conditions of the intestinal
tract
Only a fraction of the drug administered makes it to the blood stream, it must go
through the liver first. This fraction of drug that enters the blood stream is called
bioavailability. First pass
Distribution
The process of drugs moving throughout the body is called distribution and it
happens after the drug reaches the site of action
, 2
Distribution can occur by transfer, passive diffusion or the drug distribution can be
changed by transport systems that may pick to transport or exclude dugs based on
Size, charge or structure.
Diffusion can influence distribution.
Drugs can be distributed faster if they are small, uncharged and have a good
balance between water and lipid solubility. Passive diffusion- permeable barriers,
smaller molecules get to distributed better
Plasma protein binding
If not, protein bound; its higher in blood and tissues
Drugs passively diffuse and distribute when they are unbound and uncharged.
Plasma proteins- is when drugs bind to protein in the bloodstream. They are
produced in the liver and their presence in the bloodstream affect liver function,
nutritional status and disease. For example: Albumin.
Other plasma proteins include alpha-1-acid glycoprotein, cortisol-binding
globulin, sex hormone–binding globulin, and lipoproteins.
Drugs bound to plasma proteins can freely circulate in the bloodstream rather than
be distributed by passive diffusion from their site of absorption, so plasma protein
binding helps normalize concentrations throughout the body.
Drugs bound to protein are protected from metabolism in the liver and from
excretion by the kidneys. They stay longer in the body actively.
Protein can extend the period of time that drugs remain in the body; this is very
important.
If a patient does not have the proper nutrition state, or disease that alters protein in
the body, may not be up to par.
For example: cancer patients, liver disease, MI, stress and infection
Advantages: Protein can protect drugs from metabolism and excretion; extending
the time of the drug in the body
Disadvantage: the general principle that drug action occurs through free, unbound
drug. Protein binding also prevents the interaction of drug at the site of action.
, 3
Plasma protein hold drugs in the circulation and prevents their distribution to other
sites in the body. Example: Digibind
Drugs bound to plasma proteins cannot interact with their receptor. Example
Warfarin, 98% is bound to plasma protein, and only 2% is free and unbound to
produce an effect.
Storage
Lipoic accumulate in fats, calcium in teeth
Metabolism
Metabolism is important in drug activity. Drugs when metabolized turn into
metabolites
Drugs that are lipid soluble or weakly acidic or basic may not readily be excreted
from the body. It has to be water solubility to be excreted by the kidneys.
Metabolism is the process of changing one chemical into another, and the process
usually either creates or uses energy.
Metabolism occurs mostly in the smooth endoplasmic reticulum of cells in the liver
Metabolism by the liver following oral administration is called first-pass
metabolism and is important in determining whether a drug can be orally
administered.
Phase I – non-synesthetic- drugs are oxidized or reduce to prepare the drug for
further metabolism. Unmask polar. Oxidized, unmask, converted more into water
solubility
Phase I reactions introduce unmask polar groups- they improve water solubility
and prepare them for further metabolic reactions.
Metabolites with greater or lesser pharmacological activity
Phase I are rapidly eliminated if they are not, they go to Phase II
Phase II – synthetic- polar group like glutathione is conjugated to the drug
Something is added to the drug to synthesize a new compound.
Metabolites to polar molecular such as glucuronic acid, glycine,
sulfate, or acetate by enzymes make metabolites more water soluble
and excreted by the kidneys more readily.
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