Pharmacodynamics Flashcards
Clearance of drugs via plasma include which routes? What does elimination affect?
all - renal, hepatic, biliary, pulmonary, salivary, mammary, skin
affects the time a drug remains in the body and the dosage required
What is the primary site of drug excretion?
renal (volume of plasma that gets filtered of drug per unit time)
What are the 3 processes of renal clearance? Provide an explanation for each.
glomerular filtration - filtration of smaller molecules, free drug will be filtered
tubular secretion - active, carrier mediated
tubular reabsorption - reabsorbs remaining drug, control rate of reabsorption by altering the pH of the urine
List some factors that will demonstrate decreased drug clearance. (3)
elderly patients/newborns, kidney/cardiac disease, secretion inhibitors
Describe hepatic and biliary excretion.
clearance through biotransformation to metabolite, is the volume of blood perfusing the liver that is cleared of the drug per unit of time, is effected by blood flow, protein binding, and activity of enzymes/transporters
drugs may be reabsorbed when passing through intestines from liver enterohepatic re-circulation
Describe pulmonary excretion.
simple diffusion, rate of elimination not constant
Describe salivary excretion.
alkaline pH, non-ionized and lipid-soluble drugs excreted passively
Describe mammary excretion.
excretion of drugs in milk, non-ionized and lipid soluble drugs will diffuse passively
Describe skin excretion.
e.x. alcohol, salicylic acid, heavy metals and can cause skin irritation
What is formula to determine maintenance dosing.
dosing rate (mg/hr) = CLp (L/hr) x plasma concentration (mg/L)
Define and describe plasma half-life.
time required for the concentration of a drug in the blood to decrease by 50%
Define critical threshold.
min. concentration of drug needed for therapeutic effect
Describe a local vs. systemic effects of aerosols.
local - upper/lower respiratory tract
systemic - absorbed and distributed via blood
What is the formula for the L/T ratio? What does the L/T ratio represent?
lung availability/total systemic availability
efficiency of aerosol drug delivery to lung
*goal in treating respiratory disease is to INCREASE L/T ratio
List some factors that will increase L/T ratio.
efficient delivery devices, inhaled drugs with high first pass metabolism, mouth washing
How does the structure-activity relationship effect drug duration?
differences in chemical structure may lead to the same effect but have different durations due to metabolism
Describe the drug-receptor interaction.
majority of drugs believed to exert their effects by combining with a specialized area on the cell or within the cell on receptors
drugs mimic natural molecules
Describe the different drug-receptor conditions.
lipid soluble drugs and intracellular receptor activation, attachment to extracellular protein activating an enzyme system, attachment to surface receptor and opening of ion channels, attachment to a transmembrane receptor
How does degree of specificity relate to drug side effects?
the greater the specificity for different molecules, the greater the degree of specificity the receptor has for a different drug, the fewer the undesirable effects and greater drug efficacy
Describe the process of lipid soluble drugs and intracellular receptor activation.
drug crosses lipid bilayer to cell membrane, binds DNA sequences, nucleus sends out info via mRNA which will change how the cell reacts to a/w irritant, leads to altered transcription and cell response
Describe the process of drug related ion channels.
drug binds to receptor on cell surface, receptor opens channel (increased conductance of ion)
Describe the process of receptors linked to G proteins.
3 components:
drug receptor - polypeptide spanning cell membrane 7x
G protein - guanine nucleo peptide binding protein (GDP, GTP)
effector system - enzyme (second messenger), ion channel (outflow of K)
drug binds to receptor, receptor/protein complex undergoes structural changes, a subunit dissociates and regulates target proteins (stimulatory vs inhibitory)
Describe agonists.
drug that has the ability to produce a desired therapeutic effect when bound to the receptor
produces same response as endogenous that binds to that specific receptor
Describe antagonists.
drugs that produce no receptor response when bound to the receptor
can prevent endogenous chemicals or other drugs from having an effect, compete with agonists for receptor sites
Describe competitive antagonists.
drugs that compete with agonist or endogenous molecule for a single site on the receptor, drug present in greatest number will bind, common for antidotes
Describe non-competitive antagonists.
drug inactivates the receptor (partial vs complete) by binding (different site than agonist)
Describe high affinity.
high rate or associating with a receptor then the rate of dissociating from a receptor
*most drug-receptor binding is reversible
Describe receptor saturability.
occurs when all available receptors are occupied, increasing the drug concentration will not increase therapeutic effect, receptor binding does not necessarily mean that effect will be stronger, will increase the risk of adverse effects
Some drugs bind to enzymes and _____ their action on cells.
block
Describe non-specific drug interactions.
no receptor action, interaction with microorganisms
Define onset of drug action
the time is takes after the drug is administered to reach a concentration that produces a response
Define duration of action.
the time during which the drug is present in a concentration large enough to produce a response
Define maximal effect.
point at which the drug reaches its highest effective action
Define trough level.
period immediately before.a drug is given in a repeated dosing regimen (lowest drug concentration)
Define median effective dose.`
dose of a drug necessary to produce the desired intensity of effect in one half-life of all patients (ED50)
Define lethal dose.
dose of a drug that elicits an undesirable toxic or lethal reaction in one half-life of all patients (LD50)
Define therapeutic range.
plasma drug concentration between minimum and toxic concentrations
Describe drugs with wide vs narrow therapeutic index. What is considered ‘low or narrow’ and what does this require?
wide therapeutic index - high safety margin, relatively safe, lethal dose in great excess of therapeutic dose
narrow therapeutic index - more dangerous, small increased over normal doses may induce toxic reactions
<2, requires close monitoring
Define loading dose.
higher amount of drug given once or twice to achieve maximum effective dose quickly
Define maintenance dose.
intermittent doses given to maintain plasma levels
Define tolerance.
increased amount of a drug is needed to produce the same effect
Define tachyphylaxis.
rapidly developing tolerance
Define ADE.
adverse outcome to medication administration
Define ADR.
unintended, undesirable, unpredictable drug effects
Define adverse effects.
unwanted/unintended action that may occur during drug therapy
Define side effects.
undesirable but mild pharmacological effects of a drug, predictable
Define toxic effects.
life threatening, characteristic toxic effects, due to accumulation or intentional use
Define teratogenic effects.
drug-induced birth defects which follow drug therapy in pregnant women
Describe additive effects.
2 + similar effect drugs are combined, result = sum of individual agents, each drug is given in lower dose for an equal effect of either drug given separately
- 1 + 1 = 2*
Define synergism.
harmonious action of 2 unlike drugs producing an effect which is greater than the total effect of each drug acting by itself
1 + 1 = 3
Define potentiation.
one drug improves the performance of the other drug
1/2 + 1 = 2
Define idiosyncratic reactions.
unusual, unexpected reactions to a drug, which may have genetic cause, person may experience opposite reaction to the desired one
True or false, reactions may decrease with repeated exposure to the drug.
F
Define anaphylaxis.
systemic reaction - deem of a/w, severe hypotension, cardiac arrhythmia
