2. Pharmacokinetics, Pharmacodynamics, and Pharmacogenetics Flashcards
process of drug movement through the body that is necessary to achieve drug action
pharmacokinetics
4 processes of pharmacokinetics
- absorption
- distribution
- metabolism
- excretion
movement of the drug into the bloodstream
absorption
purpose of enteric coated drugs (EC)
resist disintegration in the gastric contents of the stomach (wait until small intestine)
T/F: enteric coated (EC) drugs and extended release (ER) drugs should not be crushed
True
Which route is going to be absorbed the quickest?
IV (already in the bloodstream); IM and subcutaneous will both be quicker than oral (enteral)
Which version of transport will be absorbed quicker: active or passive?
Passive; does not require molecules or energy -> can diffuse across membranes
What types of molecules cannot diffuse across membranes (passive)?
water-soluble and ionized (positively or negatively charged)
What types of molecules can diffuse passively across membranes?
lipid-soluble and nonionized
oral drugs pass from intestinal lumen to the liver via the portal vein and undergo metabolism -> reduces amount of active drug
first pass effect
percentage of administered drug available for activity
bioavailability
Factors that alter bioavailability
- drug form
- route of administration
- gastric mucosa and motility
- administration w/ food and other drugs
- changes in liver metabolism (liver dysfunction)
movement of drug from circulation to the body tissues
distribution
What occurs w/ drugs that are highly protein-bound?
less active drug available -> drug bound to protein is inactive
What is the effect of taking at least 2 meds that are both highly protein-bound?
both drugs will compete for protein binding -> higher free active drug -> may need smaller dose
What types of drugs are able to cross the blood brain barrier (BBB)
highly lipid soluble and of low molecular weight can cross by diffusion while other may cross via transport proteins
What is considered before giving drugs during pregnancy?
risk-to-benefit ratio
process by which the body chemically changes drugs into a form that can be excreted; aka biotransformation
metabolism
liver enzymes that covert drugs into metabolites
cytochrome P450 enzymes
time it takes for the amount of drug in the body to be reduced by half
half life
occurs when the amount of drug being administered is the same amount of the drug being eliminated
steady state (plateau drug level)
What is a loading dose?
a large initial dose of a drug w/ a long half life -> allows therapeutic effects to take place while reaching a steady state
elimination of drugs from the body
excretion
main route of drug excretion
kidneys
What must you be aware of when administering drugs?
renal lab values (will the drugs be excreted properly)
study of effects of drugs on the body
pharmacodynamics
amount of drug needed to elicit a specific physiologic response
potency
high vs low potency
- high: produces significant therapeutic response w/ low concentration
- low: produces minimal therapeutic response at low concentrations
point at which increasing a drug’s dosage no longer increases desired therapeutic response
maximal efficacy
describes relationship between therapeutic dose of a drug (ED50) and the toxic dose of a drug (TD50); difference between the 2 points
therapeutic index (TI)
dose of drug that produces a therapeutic response in 50% of the population
ED50
dose of a drug that produces a toxic response in 50% of the population
TD50
What does it mean if a drug has a narrow (low) therapeutic index?
the therapeutic dose and toxic doses are close together -> require close monitoring for pt safety
highest plasma concentration of a drug at a specific time; indicates rate of absorption; usually 30-60 minutes by IV
peak drug level
lowest plasma drug concentration; drug level drawn right before next dose without regard to administration
trough drug level
What determines the activity of most drugs?
ability of the drug to bind to a specific receptor; more active the better the drug fits at the receptor site
drugs that activate receptors and produce a desired response
agonists
drugs that prevent receptor activation and blocks a response
antagonists
T/F: antagonists only decrease cellular action
False; may increase or decrease cellular action depending on the action of the chemical messenger that is blocked
drugs that affect multiple receptor sites
non-specific drugs
drugs that affect multiple receptors types
non-selective drugs
7 mechanism of drug actions
- stimulation
- depression
- irritation
- replacement
- cytotoxic action
- antimicrobial action
- modification of immune status
unintentional, unexpected reactions to drug therapy that occur at normal dosage; may be mild to life-threatening
adverse drug reactions (ADRs)
secondary effects to drug therapy
side effects
T/F: all drugs have side effects
True
Most common side effects found in drugs?
N/V/D
occurs when drug levels exceed a therapeutic range; may be due to overdose or drug accumulation
drug toxicity
refers to study of genetic factors that influence an individual’s response to a specific drug
pharmacogenetics
decreased responsiveness to a drug over the course of therapy; individual will require higher dosage of drug to achieve same therapeutic response
Drug tolerance
acute, rapid decrease in response to a drug; may occur after first dose or several doses
tachyphylaxis
drug response not attributed to the chemical properties of the drug; can be positive or negative; psychological origin but physiologic response
placebo effect
changes that occur in the absorption, distribution, metabolism, and excretion of one or more drugs (ex. taking enzyme inducers and enzyme inhibitors together)
pharmacokinetic interactions
interactions that result in additive, synergistic, or antagonistic drug effects
pharmacodynamic interactions
when 2 drugs are administered together and the response is equal to the effects of the 2 drugs together (2+2=4)
additive effect
when 2 drugs are given together, the clinical effects of the 2 drugs is greater than their separate effects (2+2>4)
synergistic effect
when 2 drugs are administered together and one drug reduces or blocks the effects of the other (2+2<4)
antagonistic effect
Name 4 things drugs can interact with?
- other drugs
- nutrients: foods increase/decrease or delay body’s response to drugs (grapefruit and CYP450 enzyme)
- labs: cephalosporin can alter urine glucose/ketone tests
- photosensitivity: skin reaction from sunlight (usually UVA); causes photosensitive and photoallergic reactions
List 4 receptor families
- cell membrane-embedded enzymes
- ligand-gated ion channels
- G protein-coupled receptors
- transcription factors
drug binds to domain on cell surface -> activates enzyme inside cell which causes response (fast acting)
cell membrane-embedded enzymes
channel crosses the cell membrane -> when it opens, ions flow in and out -> mainly affects Na and Ca (fast acting)
ligand-gated ion channels
drug activates receptor -> receptor activates G protein -> binds w/ GTP -> activates the effect (fast acting)
G protein-coupled receptors
found in the cell nucleus on DNA -> activation regulates protein synthesis (prolonged)
transcription factors
drugs that increase drug metabolism -> promote drug elimination and decrease plasma concentration (decreased action)
enzyme inducers
drugs that decrease drug metabolism -> increase plasma concentration and potential toxicity
enzyme inhibitors
