Basic Principles of Pharmacology Flashcards
Elicits response for which it is given
Effective
Cannot produce harmful effects
Safe
Elicits only responses for which it is given
Selective
Additional properties of an ideal drug
reversibility, predictability, ease of administration, freedom from drug interactions, low cost, chemical stability, simple generic names
Factors that determine intensity of drug responses
administration, pharmacokinetics (ADME), pharmacodynamics, individual variation
Dosage, route, time
administration
What the body does to the drug
pharmacokinetics
What the drug does to the body
Pharmacodynamics (d in dynamics = what drug does)
Drug interactions, physiologic variables, pathologic variables, genetic variables
Individual variation
Pre-administration assessment includes
collect baseline data (HR, BP), identify high risk patient (multi drug), assess patient capacity for self care (educate, teach back, how to administer)
Federal pure food and drug act
set standards for drug quality and purity, in addition to strength
Food, drug, and cosmetic act
all medications must be tested for safety, with results viewed by FDA
Harris-Kefauver agreements
Medications must be proven effective before marketing
Controlled substance act
Rules made for categorizing medications with potential for abuse
BPCA & PREA
Promote research in drug safety and efficacy in children with clinical trials
FDA amendments act
Include rigorous oversight of drug safety after approval
Controlled substances class I (++++)
high abuse potential, no accepted medical use
Examples of class I controlled substances
heroin, LSD, MDMA (ecstasy), marijuana
Controlled substances class II (++++)
high abuse potential, accepted medical use
Examples of class II controlled substanses
morphine, oxycodone (OxyContin), methamphetamine, fentanyl, Adderall
Controlled substances class III (+++)
moderate abuse potential, accepted medical use
Examples of class III controlled substances
ketamine, testosterone, anabolic steroids
Controlled substance class IV (++)
low abuse potential, accepted medical use
Examples of class IV controlled substances
Xanax, Valium, Ambien, tramadol
Controlled substance class V (+)
low abuse potential, accepted medical use
Examples of class V controlled substances
Lyrica, Lomotil, many codeine-containing cough syrups
What class has the highest abuse potential and which class has the lowest
Highest = class I
Lowest = class V
Most reliable way to objectively assess drug therapies
Randomized controlled trials
Three key features to randomized controlled trials
controls, randomization, blinding
Chemical medication nomenclature
describes the medication using chemistry nomenclature (N-acetyl-para-aminophenol)
Generic medication nomenclature
name of drug assigned by US Adopted Names Council that is less complex than chemical name (acetaminophen)
Trade medication nomenclature
name under which drug is marketed under for ease of use and recall (Tylenol, Ofirmev, APAP, Excedrin)
Sources of drug information
People (pharmacists, nurses, physicians), pharmaceutical reps), reference books, online database
Pharmacokinetics
what the body is made to do to the medication
Kinetics - ADME stands for
absorption, distribution, metabolism, excretion
Absorption of drug
movement from site of administration to blood stream, rate of absorption determines how soon effects will begin, amount of absorption determines how intense effects will be
Distribution of drug
movement of drugs into cells (IV is straight to distribution)
Metabolism of drug
biotransformation or conversion of drugs into another form
Excretion of drug
removal of drug from the body
Elimination of drug
both metabolism and excretion combined
Factors that can affect absorption
rate of dissolution, surface area (small intestine absorbs more), blood flow, lipid solubility, pH partitioning (acid base)
Most common routes of drug administration
IV, IM, SQ, and PO
Advantages of Intravenous route
rapid onset, permits large volumes and irritant drugs
Disadvantages of IV route
irreversible, inconvenient, and expensive, not suited for self administration, risk for fluid overload, infection, and embolism, drugs must be WATER SOLUBLE
IM and SQ injections barrier
capillary wall
IM and SQ advantages
permits use of poorly soluble drugs and depot preparations
IM and SQ disadvantages
uncomfortable, possibly painful, inconvenient with potential for injury
PO (oral) barriers
epithelial lining of GI tract and capillary call, makes absorption slower and variable
PO advantages
easy, convenient to administer, inexpensive, ideal for self administration, potentially reversible
PO disadvantages
variability, inactivation by gastric acid and digestive enzymes; possible nausea/vomiting, patient must be conscious and cooperative
Distribution of drug
transport of drug in body fluids from bloodstream to various tissues in body, and then site of action
Factors affecting distribution
blood flow to tissues, fluid status, alterations to vessels & abscesses
What type of drugs can cross the BBB (blood brain barrier)
lipid soluble drugs or those with a transport system can cross the BBB
What do drugs bind to in the bloodstream
albumin, only unbound drugs can act on body
What two structures can limit access of medications to certain parts of body
Blood brain barrier, placenta
First pass effect
drugs that are highly metabolized lose much of their effectiveness due to first pass effect, may need higher doses or be administered via a different route to achieve therapeutic effect
Removal of drugs from the body in the urine, bile, sweat, saliva, breast milk, and expired air, manipulating urinary pH can promote drug ionization and decrease passive reabsorption
Excretion
Plasma drug levels
helps determine appropriate dosages, routes, and therapeutic effectiveness
Trough
low point before dose due
Peak
30 minutes after completed
Half-life
time required for the amount of drug in the body to decrease by 50%
Pharmacodynamics
what the drug does to the body, the effect is the turning on, off, promotion, or blocking of a response the body can already perform
By knowing how drugs affect the body, nurses can
provide patient education, make decisions with PRN medications, evaluate patients for drug responses, collaborate with prescribers
Efficacy (effectiveness)
largest effect that a drug can produce, increased height on the dose-response curve indicates more efficacy
Potency
how much of a drug is needed to elicit a response
Medications can affect four primary receptor families
cell membrane-embedded enzymes, ligand-gated ion channels, protein-coupled receptor systems, transcription factors
Selectivity of drugs
more selective drugs will produce fewer side effects, opioids help relieve pain by acting on mu receptors in the CNS
ED50
dose required to produce defined therapeutic response in 50% of the population
LD50
dose that is lethal to 50% of animals treated
Therapeutic index
measure of drugs safety using the ratio of LD50 to ED50; the higher the number the safer the drug
Drug interactions
occurs whenever a patient takes two or more drugs and can be either intended or unintended and includes prescription drugs, OTC drugs, caffeine, nicotine, alcohol, illicit drugs
How do antacids cause altered absorption
increases the ability of basic drugs to cross membranes
How can Phenobarbital alter metabolism
accelerating metabolism of contraceptives, thus losing protection from pregnancy
What happens when you increase urinary pH
alter excretion by decreasing passive reabsorption
Nurses can help minimize adverse interactions by
minimizing number of drugs patient receives, take thorough history, adjust dosage, monitor for s/s toxicity
How can calcium reduce absorption of tetracyclines
creates non-absorbable complexes
Consuming food with saquinavir, type of antiviral for HIV can
increase absorption of the medication
Grapefruit juice effect
Furanocoumarins and flavonoids can inhibit CYP3A4 metabolism and increase blood levels of certain medications; instead of being metabolized, more of the drug enters the blood and stays in the body longer.
Medication instructions “with food”
take with or shortly after meal
Medication instructions “on an empty stomach”
1 hour before meal or 2 hours after
Adverse effect
any noxious (harmful), unintended, and undesired effect, ranging from mild to life threatening, that occurs at normal drug doses
Side effect
nearly unavoidable secondary drug effect produced at therapeutic doses
Organ-specific toxicity
nephrotoxicity, pulmonary toxicity, ototoxicity
Hepatotoxicity
medications are leading cause of acute liver failure due to metabolism converting drugs to toxic products, monitor ALT and AST, assess for s/s liver injury
Prolonged QT intervals creates risk for
dysrhythmias
Pharmaceutical industry role in minimizing adverse drug reactions
produce safest medications possible
Prescriber role in minimizing adverse drug reactions
select least harmful drugs, balance risk and benefits
Nurses role in minimizing adverse drug reactions
evaluate patients for ADR, educate
Medication guides are required when
patient adherence to directions for drug use is essential for efficacy, patient needs to know about potentially serious effects when deciding to use a drug
Black box warnings
strongest warning on drugs, alerts prescribers and patients to potentially severe side effects
Medication errors
any preventable event that may cause or lead to inappropriate medication use or patient harm; human factors, communication mistakes, and name confusion account for 90% of all errors
