Pharmacology Exam 1 Lecture 1-3 Flashcards
What is the study of pharmacology
the study of drugs and their interactions with the human body
What does the topic of pharmacology embrace
it embraces the knowledge of the source, physical and chemical properties, compounding, physiological actions, absorption, fate and excretion, and therapeutic use of drugs
A drug is defined as what?
any chemical agent that affects living protoplasm
What is an adverse drug reaction?
-any response to a drug in which is harmful and unintended -occurs at doses used in man for prophylaxis, diagnosis or treatment -side effects, drug allergies and drug interactions
What are the four main processes of pharmacokinetics?
Absorption, distribution, metabolism(biotransformation), and elimination of drugs
Pharmacokinetics is defined as what?
the action of the body on the drug. It is the study of the fate of drugs on the body
Why is it important to understand and apply pharmacokinetic principles?
it can increase the probability of therapeutic success and reduce the occurrence of adverse drug effects in the body
What is the tool used to design optimally beneficial drug therapy regimens?
proper drug, route of administration and dosing schedules
absorption is defined as
movement of a drug from its site of administration into the central compartment and the extent to which this occurs
If you have a solid dose form of a drug what must happen before the drug can be absorbed
there must be dissolution of the tablet or capsule thus liberating the drug
What are clinicians more concerned with when it comes to ADME?
bioavailability rather than absorption
What must occur in order for a drug to be absorbed?
it must be lipid soluble in order to have site access
Absorption occurs by what mechanisms
Active or passive transport Ionized or non-ionized
What is active transport
against a concentration gradient and requires energy
what is passive transport
diffusion from higher to lower concentration
What is a site where there is a high probability for drug interactions
during movement through the GI tract
What is distribution
when a drug is transported to site where is reacts with various body tissues or receptors
After absorption or systemic administration where does a drug go
it is distributed into interstitial and intracellular fluids
What are the factors that affect distribution of a dug into tissue
Cardiac output, regional blood flow, capillary permeability and and tissue volume
What parts of the body would receive most of a drug
Initially Liver, Kidney, Brain and other well perfused organs
The second distribution phase is faster or slower?
slower
What parts of the body do the second distribution phase affect
it involves delivery to muscle, most viscera, skin and fat
Where does most of the drug get delivered from second phase distribution?
extravascularly
What are important factors that determine distribution
Lipid solubility Transmembrane pH gradients
What happens when a drug is bound to plasma proteins and tissue macromolecules?
it limits the concentration of free drug
Lipid soluble drug have a high affinity for what
adipose tissue
Why do drugs get stored in the adipose tissue
there is low blood flow there creating a drug resivoir
What are highly lipid soluble class of drugs
Barbiturates, Phenothiazines, Benzodiazepines
What is the function of metabolism
to convert active lipid soluble compounds and convert them to inactive water soluble substances to be excreted by the kidneys
Where are most drugs metabolized?
in the liver, but it can also happen in the kidneys, lungs and intestinal tract
What happens during Phase I of metabolism
Hepatic microsomal enzymes first oxidize, demethylate and hydrolyze drugs
During what phase of metabolism do more drug interactions happen?
Phase I hepatic enzymes
Where do drug with a short half life and inactive metabolites get metabolized
they are metabolized during phase I which causes them to be less effected by drug interactions
What happens during Phase II of the metabolism
large water soluble substances(glucuronic acid, sulfate) are attached to the drug.
How many times may drugs circulate thru the phases of metabolism
drug can circulate through one or both phases multiple times until the water soluble characteristic is present
What are the important hepatic microsomal enzymes of Phase I metabolism
CYP 450
What is the CYP classification for enzymes
CYP #X# #=family denoted by a number X=subfamily denoted by letter or arabic number X=individual gene denoted by a number
What are the CYP families primarily involved with drug metabolism?
CYP1,CYP2,CYP3,CYP4
How does enzyme inhibition effect the concentration of drugs?
It decreases the rate of metabolism of object drug by obstruction metabolizing enzymes. This leased to an increase in drug concentration
How would enzyme inhibition effect half life
it increases half life, which causes it to accumulate
What is the effect on the clearance of a drug when you induce an enzyme. What does this do to the concentration of the drug?
stimulates the increase in CYP 450 enzyme activity which increases the clearance of drug. This decreases the concentration of a drug
What is an example of a prototypical inducer
Phenobarbital it induces all enzymes
What is excretion/elimination?
process that removes the drug and its metabolites from the body
What are the primary ways drugs are excreted?
through the urine, feces, skin
How are drugs eliminated from the body?
they are eliminated either unchanged or converted to its metabolites
Excretory organs excluding the lungs eliminate what type of compounds more efficiently?
they eliminate polar compounds more efficiently that substances with high lipid solubility
What organ is the most important organ for excreting drugs and their metabolites?
the kidney
What happens to a drug when it is excreted through the feces?
substances are usually unabsorbed orally ingested drugs
how are unabsorbed drug metabolites excreted?
either in the bile or directly into the intestinal tract and not reabsorbed
why is excretion of drug through breast milk important?
because the excreted drugs are a potential source of unwanted pharmacological effects in a nursing infant
The lungs are important mainly for the excretion of what?
anesthetic gases
What are factors about a patient that can effect the basic pharmacokinetic principles
age, sex, weight, disease states and genetic factors
What is pharmacodynamics
action of the body on the drug
Pharmacodynamics is the study of what
biochemical and physiological effects of drugs and their mechanisms of action
What are the most common mechanism for drug interactions?
synergism, antagonism, altered cellular transport and effects on receptor sites
What is the benefit of understanding pharmacodynamics?
provides the basis for the rational therapeutic use of a drug and the design of a new superior therapeutic agents
What are the 4 most important parameters governing drug disposition are?
Bioavailability Volume of distribution Clearance Elimination
What is Bioavailability?
(F) The fractional extent to which a dose of drug reaches its site of action
What are factors that decrease bioavailability (F)
GI absorption 1st pass effect Metabolism (enzymes, active transport)
What is the route of administration based on
the understanding of the factors that decrease bio-availibility
What is volume of distribution?
it related the amount of drug in the body to the concentration (it doe not necessarily refer to an identifiable physiological volume but rather to the fluid volume that would be required to contain all of the drug in the body at the same concentration measured in the blood or plasma
What is half-life (t1/2)
the time is takes for the plasma concentration to be reduced by 50%
How many half life’s does it take to get to a steady state?
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