Pharmacodynamics Flashcards
Therapeutic index
- a measure of the safety of a drug.
- the ratio of the lethal dose in 50% of the patients and the minimum dose at which therapeutic effect occurs
- at what amount of med does it become toxic or lethal and at what does is it therapeutically effective
- need to assess narrow index more safely.
A higher dose would create…
a greater effect
If a dose is doubled the response would have…
twice the effect
Symptom unique to Digoxin toxicity
Halos around objects
Potency
- the relative amount of drug required to produce a desired response.
- a drug that is more potent will produce a therapeutic effect at a lower dose.
Efficacy
a measure of the magnitude of the maximal response in a patient that can be produced from a particular drug
- more important than potency - at what point will we see a therapeutic effect
Drug actions (the mechanism of drug actions in living tissues)
- receptor interactions
- enzyme interactions
- nonspecific interactions
Drug effect (the physiologic reaction of the body to the drug)
- Drug potency and therapeutic index
Receptor Interactions
a molecule to which a medication binds to initiate its effect. can be selective or nonselective
Selective receptor interaction
binds with only one type of receptor
Nonselective receptor interaction
binds with several types of receptors
Agonist
a drug can produce a response that mimics the effect of the endogenous regulatory molecule
Partial agonist
a medication that produces a weaker or less effective response than an agonist
Antagonist
Can be:
Block a receptor
- competitive (compete with agonist for receptor sites - will lose if there is more agonist)
- non competitive (binds with receptor sites and blocks the effects of the agonist no matter the dose, always wins) - functional (does not bind to receptor, works against agonists to slow drug absorption of speed up metabolism or excretion)
Enzyme Interactions
For a drug to alter enzyme interactions, it must inhibit a specific enzyme by fooling it
- the enzyme binds to the drug instead of to the normal target cell
ACE (angiotensin converting enzyme)
normally causes the production of angiotensin II (vasoconstriction)
- ACE inhibitors fool ACE into binding to them instead.
- less angiotensin II is made and therapeutic response is that BP is lowered.
Nonspecific Interactions
- Doesn’t directly involve receptors or enzymes
- instead, cell membranes or metabolic processes are the biochemical target
Once the drug is at the site of action it can…
modify the rate (increase or decrease) at which the cells or tissues function
Pharmacotherapeutics
use of drugs in practice
seeking therapeutic responses
- the use of drugs and the clinical indications for drugs to prevent and treat diseases
Acute therapy
ie, in ICU or trauma rooms - high risk meds in controlled environments
Maintenance therapy
ie, chronic disease management. HTN, DM 2 meds
Supplemental therapy
TPN, insulin
Palliative therapy
care vs cure; narcotics, anti-anxieties
Supportive therapy
supports physiologic needs, ie. fluids & electrolytes, blood products, oxygen
Prophylactic thearpy
ABX for asplenic pts
Empiric therapy
based on precedence rather than research. ie, use of acetaminophen in a fever of unknown origin
Nurses role in preventing and managing drug effects
- obtain medical history
- prevent medication errors from occurring
- thoroughly assess the client and all diagnostic data
- monitor carefully
- know the drugs
Know the Drugs - The effectiveness of drug therapy must be evaluated
- one must be familiar with the drugs:
- intended therapeutic action (beneficial)
- unintended but potential side effects (predictable, adverse reactions)
Monitoring Pharmacotherapy carefully
- therapeutic index
- drug concentration
- patients condition
- tolerance and dependence
- interactions
- side effects/adverse drug effects (potential lethal and most common)
Adverse Drug Reaction
an adverse outcome of drug therapy in which a patient is harmed in some way
Pharmacologic Reations
In works too well. antihypertensive leads to extreme hypotension
Idiosyncratic reactions
particular to the patient, but not a true allergy or a pharmacologic reaction. Eg, pt develops migraine with Percocet
Allergic reaction
allergies - patient’s immune system decides to treat a drug as a dangerous character and overreacts
Teratogens
anything that can damage the fetus. alcohol and cocaine. cause birth defects
Dose dependent effect
- some adverse drug reactions are classified as side effects:
expected, well-known reactions that result in little or no change in patient management
occur with predictable frequency
the effects intensity and occurrence are frequently related to the size of the dose.
Drug toxicity
- nephrotoxicity
- neurotoxicity - especially sensitive to small amounts of toxic substances.
- hepatotoxicity
- Dermatological
- Bone marrow
- Cardiotoxicity
- Skeletal Muscle and Tendon
Additive Effect
when two drugs are given together and they add to the others effectiveness
Synergistic effect
multiplication of magnitude. equals more than they would on their own.
Antagonistic effect
two drugs are given and one can cancel out the effects of the other. or one may increase the excretion
Incompatability
- when parenteral drugs are mixed together and form a precipitate that can be lethal
