Drug actions Flashcards
The nurse must have knowledge of the pharmacokinetic and pharmacodynamic phases of drug action to:
-adequately assess, plan, intervene and evaluate drug effects.
Processes of drug absorption:
- passive
- active
- pinocytosis
Passive diffusion (absorption)
O
Active diffusion (absorption)
o
Pinocytosis (absorption)
o
First-pass effect:
in the liver
Bioavailability (Affected by)
- drug form
- route of administration
- GI mucosa and motility
- food and drugs
- changes in liver metabolism caused by liver dysfunction or inadequate hepatic blood flow
IV drugs
100% of drug is in systemic circulation.
30% may be bound to protein
70% to be used up
Low
O
Moderate
o
High
o
Protein binding
- drugs are distributed in the plasma many are bound to varying degrees with protein (albumin)
- portion that is bound is inactive
- not available to receptors
- drugs compete for protein sites
Blood brain barrier
highly lipid soluble drugs cross
Placenta
lipid soluble and lipid insoluble cross
Metabolism (Bio transformation)
-liver=primary site
Half-life
- time it takes for one half of the drug concentration to be eliminated affect half-life.
- metabolism and elimination affect half-life.
excretion (elimination)
- kidney: primary site
- creatinine clearance
- urine ph affects drugs excretion
Sodium bicarbonate
neutralizes acids (respiratory/cardiac arrest)
Pharmacodynamics
-study of way drugs affect the body
(Drug concentration and its effect of the body)
-primary effect is desirable
-secondary effect may be desirable or undesirable.
Dose response and maximal efficacy
- every medication has a maximum drug effect.
- Relationship between minimum amount vs maximum amount of the drug needed to produce the desired response.
Onset
-time it takes to reach the minimum effective concentration.
Peak
-highest blood concentration
Duration of action
-length of time a drug has a pharmacological effect
Receptor theory
- how drugs get used up.
- how they affect the body.
Agonist
produce response.
Antagonist
block a response
Categories of drug action
- stimulation or depression
- replacement
- inhibition or killing of organisms
- irritation
Specific/non specific effects
o
Nonselective drug effect
o
Therapeutic index
o
Peak and trough levels
o
Loading dose
o
Side effects
o
Adverse reaction
o
Toxic effects
o
Drug interactions
o
Drug incompatibility
o
Absorption (pharmacokinetics)
two or more drugs taken at the same time can cause the absorption rate of one or more of the medications to change.
Distribution (pharmacokinetics)
two drugs that are highly protein bound and administered together can result in drug displacements.
Metabolism (pharmacokinetics)
many drug interactions occur in the livers microsomal system.
- enzyme inhibitors.
- enzyme reducers.
Excretion (pharmacokinetics)
two or more drugs that undergo the same route of excretion may compete with one another for elimination from the body.
Pharmacodynamic interactions
- additive drug effect
- synergistic drug effect or potentiation
- antagonistic drug effect
- drug-food interactions
- drug-laboratory interactions
- drug-induced photosensitivity
