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)