Pharmacodynamics Flashcards
Therapeutic window/index
relationship between beneficial and adverse effects
Wide therapeutic window
generally considered safer
Narrow therapeutic window
closer monitoring and higher rate of dangerous toxicities
Minimal effective concentration
all drugs have a minimum blood level below which they are ineffective
Maximal safe concentration
max level above which serious side effects and toxicities may occur
Toxicity
interchangeably with adverse drug reaction or side effects. Refers to more serious or unexpected ADRS that tend to occur above the maximal safe concentration or when drug is not monitored properly
Steady State
drug input equals drug output
stabilize/plateau
4-5 half lives to occur
Onset of action
when the drug begins to take effect, depends on drug’s mechanism of action and long that takes to become physiologically visible
Duration of action
length of time a drug can be expected to exhibit its pharmacological effects
Receptor theory
drug produces an effect by combining with some specific molecular constituent (receptor). The function of the receptor or cell is modified to produce a measurable effect
Agonist
drug that mimics some natural compound by binding with the receptor and stimulating some cellular response
Antagonist
a drug that binds with a receptor, blocks the receptor from stimulation, and prevents it from being triggered normally
Affinity
strength of attraction between a drug and its receptor; describes the tightness of the bond
Selectivity
refers to the degree to which a drug acts upon one site relative to all possible sites
Alteration of Enzyme Activity
altering the activity of the various body enzymes and thus increasing or decreasing production of neurotransmitters, hormones, etc.
Adverse drug reaction
broad term that can encompass a variety of types of reactions
Adverse effect/side effect
undesired pharmacological effect of a drug
Exaggerated drug response
for example, a blood pressure medication that unexpectedly bottoms out the patients blood pressure or a sedative that makes the patient unresponsive or sedated for an extended period of time
Allergic reaction
immune system mediated, patient is usually allergic to all drugs of that same chemical class
Pseudoallergic drug reactions
reactions resemble allergic reactions but they are not mediated by the immune system; there is no antibody production
Toxicity
often used interchangeably with ADR or side effect. Toxicity refers to serious or unexpected ADRs that occur above the therapeutic window or when not monitored properly
Intolerance
term used to describe any type of ADR that the patient feels intolerable thus limiting the drug’s usefulness or acceptance to the patient
High risk drugs
include those with a narrow therapeutic window, high incidence of side effect, high incidence of allergic reactions
High risk patients
include patients who would be least likely to tolerate ADRs or loss of efficacy. (neonates/infants, elderly, frail, & malnourished; patients with difficult to control diabetes, arrhythmias, heart disease, & epilepsy
Immediate Allergic Reactions
IgE mediated activation of mast cells and basophils; generally begins within 2 hours of exposure. High potential to progress to anaphylaxis
Delayed allergic reaction
begins 6 hrs to days after exposure
Stevens-Johnson Syndrome & Toxic Epidermal Necrolysis (TEN)
blistering rash with prodromal fever & influenza-like symptoms and sloughing of skin
Pseudo-allergic Drug reactions
ADRS with symptoms that mimic drug allergy
Intolerance
broad term for any ADR that limits usefulness or acceptance of the drug by the patient
Tolerance
higher doses of a drug are needed over time to elicit the same response
Physical Dependence
the drug is needed to function normally, stopping the drug will cause withdrawal symptoms
Withdrawal symptoms
usually the opposite effects of the drug
Psychological dependence or substance use disorder
deviant behavior causing an overwhelming involvement in the use of and acquisition of a drug for euphoria
Categories of Drug Interactions
- Altered GI Absorption
- Protein Displacement
- Altered Metabolism
- Synergistic Effects & Antagonistic Effects
1) Altered GI Absorption
Altered Intestinal Flora-impact the absorption and metabolism of orally ingested drugs
1) Altered GI Absorption (altered pH)
more or less ionized, some drugs absorb better in an acidic
1) Altered GI Absorption (drug induced mucosal damage)
drugs that tear up the gut lining can reduce absorption of medications and nutrients leading to nourishment (chemotherapy)
1) Altered GI Absorption (chelation)
Chelation interactions is a form of strong chemical bonding of two substances that reduces their solubility and thus prevents oral absorption
1) Altered GI Absorption
effects of food-1 hr before food or 2 hrs after
1) Altered GI Absorption (transport protein interactions)
Transport Protein Interactions - multiple drugs competing PGPs may reduce PGP binding of one or both drugs (maybe be inhibitors or inducers of PGPs thus increasing or decreasing absorption)
2) Protein Displacement
drugs bound to plasma proteins are pharmacologically inactive & exist in equilibrium between bound and unbound. there are a limited number of binding sites available on serum albumin
3) Altered Metabolism is
concurrent administration of two drugs metabolized by the same liver enzyme system can increase or decrease in blood levels of one or both drugs; most of these interactions involve the cytochrome p450 system
3) Altered Metabolism (enzyme induction)
caused when one drug induces or speeds up the shared metabolic pathway
3) Altered Metabolism (enzyme inhibition)
most common type of drug interaction of all the different types of drug interactions. Enzyme inhibition occurs when two or more drugs create a “traffic jam”
Cytochrome p450 System
Inducers: drugs that increase metabolism
Inhibitors: drugs that reduce metabolism
Substrates: drugs that are affected by other drugs that either induce or inhibit
Pharmacogenetics: Ultra metabolizer
has higher than normal levels of certain isozymes = faster than expected drug metabolism
Pharmacogenetics: Extensive metabolizer
has normally functioning and normal levels of that isozyme and thus, metabolize drugs at expected rates
Pharmacogenetics: Poor metabolizer
abnormally low levels of certain isozymes
4) Synergistic/Antagonistic Drug Interactions
occurs when the effects of two drugs together are greater/worse than would have been predicted from each of their effects alone
Strategies to Prevent Drug Interactions
perform complete medication history
be familiar with most common drug interactions
avoid unnecessary drugs
separate chelating or pH interacting rugs
select non interacting medication
Inter patient Variability in Drug Response
Pharmokinetic differences allergy history age weight and body size disease states genetics polypharmacy complaince
Medication non adherence
degree to which a patient follows a treatment regimen
“America’s other drug problem”
just as high in pediatric population
