Pharmacokinetics and Pharmacodynamics Flashcards
Pharmacokinetics
The study of drug movement and concentration once it enters the body
What four processes drugs undergo in the body?
Absorption, distribution, metabolism, excretion
Absorption
Movement of drug molecules from the site of entry into the body to the circulating fluids.
Variables that Affect Absorption
- Dosage form
- Rate of dissolution
- Nature of absorbing surface/surface area
- Blood flow to the site of administration
- GI function
- pH
- Presence of food/other drugs
- Drug concentration
Routes of Administration
6 outlined in this lecture
- Enteral (GI Tract/Intestines)
- Parenteral (injected)
- Topical
- Transdermal
- Ophthalmic
- Respiratory Inhalation
Types of Parenteral Routes
- IV: Directly into the bloodstream (immediate)
- IM: Injected into skeletal muscle (fast)
- SQ: Injected into connective tissue or fat (slower)
- Epidural: Into epidural space of spinal column (rapid)
Distribution
Transportation of the drug to various tissues
Variables that Affect Distribution
- Blood circulation adequacy
- Protein binding
- Blood-brain barrier
What is the relationship between albumin and active drugs?
More albumin, less active drugs
Albumin decreases with…
Three things outlined in lecture
- Age
- Liver disease
- Poor nutritional status
Metabolism
The process by which drugs are inactivated or biotransformed by the body
Active Metabolites
Creates a different breakdown that has its own effects
Prodrugs
Are given as inactive drugs and are then metabolized into active drugs.
CYP isoenzyme
Involves enzymatic alteration of drug structure
First-Pass Effect
Drug is metabolized between administration site and systemic circulation or the site of action
What is the primary site for metabolizing?
The liver
Does IV have a first pass affect? Why?
No. It goes straight into the bloodstream.
Variables that Affect Metabolism (not enzyme related)
- Age, Genetics, etc.
- Nutritional Status
- Comorbidities
- Induction/inhibition by substrates also being metabolized
- Increased # of medications = Increased risk of interactions
CYP enzymes
Major enzymes that metabolize drugs
CYP Substrate
Substance that is metabolized by CYP pathways
Enzyme Inducers
- Substance that increases the production of CYP enzymes
- May lead to decreased drug effects
Enzyme Inhibition
- Substance that inhibits/decreases the activity of CYP enzymes
- May lead to enhanced or toxic drug effects
Excretion
The process by which drugs and metabolites are eliminated from the body
Serum Drug Level
Measurement of the amount of drug in the blood at a certain time
Minimum Effective Concentration (MEC)
The required amount of the serum drug level that must be present for the medication to be effective
Toxic Concentration
Excessive drug levels in the blood stream
Therapeutic Range
- Desired response with no toxicity
- Goal is to maintain drug levels in this range
Peak Concentration
- Highest serum level
- Keep below toxic concentration
Trough Concentration
- Lowest serum level
- Keep above or near MEC
Therapeutic Index
Measure of the relative safety of the
drug
Half-Life
Time needed for the drug’s serum concentration to decrease by 50%
Bioavailability
The percentage of active drug absorbed and available to reach the target tissues following administration
Bioequivalence
A term used to compare 2 products that are:
* Chemically equivalent
* Given in the same dose
* Have the same bioavailability
Pharmacodynamics
What the drugs do to the body
Drug-Receptor
Reactive cellular site where a drug interacts to produce a pharmacologic response
Agonists
Molecules that activate receptors
Antagonists
Molecules that block receptors
Partial Agonists
Moderate agonist activity
Nonspecific Drug Interaction
Produce more general effects on cell membranes and cellular processes. Do not act on receptors.
Drug-Drug Interactions
Occur when the effects of one drug are affected by prior or concurrent administration of another drug
Most common side effects
Anorexia, Dizziness, Drowsiness, Dry mouth, GI upset, Constipation
Types of adverse effects
Seven outlined in lecture
- Toxicity
- Allergic reaction
- Idiosyncratic effect- Uncommon drug response resulting from a genetic predisposition
- Iatrogenic disease
- Physical dependence
- Carcinogenic effect
- Teratogenic effect- Drug –induced birth defect
Nursing Responsibilities to Decrease or Prevent Adverse Effects
- Take a thorough medication history
- Identify high risk meds and patients
- Pregnancy possibility
- Know and anticipate major therapeutic actions of each drug you give
- Know and anticipate the major AE of each drug you give
- Know which drugs are likely to interact with other meds or foods and how it may present
- Use interventions that can minimize AE
Beer’s List
A list of medications we should try to avoid in older adults
