Pharmacology Part 1 Flashcards
What are the 3 phases of drug action?
Pharmaceutics, pharmacokinetics, pharmacodynamics
What is the pharmaceutical phase?
Includes prep of the drug for admin.
Generally role of manufacturers
Nursing role includes dilution, crushing or mixing to prepare for admin.
Clinical trials for drugs:
USP-NF: quality standards of drugs and dietary supps.
USP label verifies purity and exact amount of ingredient
FDA: eval and research for drugs/controls whether prescription or OTC drugs may be used for therapy
(must be approved)
FDA Review and Approval Process phases:
Phase I: studies safety of med/treat.
Phase 2: studies efficacy
Phase 3: studies safety, efficacy, dosing
Phase 4: studies long-term effectiveness/cost
What does pharmacokinetics mean?
What the body does to the drug
-absorption (taken into body)
-distribution (moved into tissues)
-metabolism/biotransformation (changed into a form than can be excreted)
-elimination/excretion (removed from body)
What are the route of medication?
Oral:
-80% are oral
-route convenient and economical
-drug is ingested (digested/absorbed by stomach/intestine then enters hepatic portal circulation to the liver) enters general circulation after
What can help or delay drug dissolution?
-some products used in drug may bind tighter to the drug molecule delaying drug absorption
-high fat meals can slow the rate at which contents leave the stomach slowing absorption
-pain and stress can trigger SNS slowing movement of GI slowing absorption
Routes of administration of drugs:
Sublingual (under tongue and absorbed through mucous membranes into bloodstream)
Transdermal (drug applied to skin/continuous long acting)
Rectal ( absorbed thru mucous membranes may be irregular though or incomplete)
Parenteral: IV>IM>SQ (rapid, avoids unpredictable absorption in GI tract, more costly, cannot b retrieved)
What does absorption include?
process of moving drug from site of admin. into circulation
drug must cross many tissue membranes to get to circulation
diffusion occurs along a conc. gradient so available drugs will migrate into cells when conc. is lower (passive diffusion, facilitated diffusion, active transport)
What affects absorption rate?
Blood flow, pH, Gi motility, stress, age, disease states, co-admin. drugs or food
What is bioavailability of a drug?
Describes what portion of the administered drug is available to produce a pharmacologic response
Oral drug must pass thru intestinal wall and then the portal circulation to liver (both common sites of first pass effect)
First pass effect:
allows the live to metabolize or inactivate drugs and potentially harmful substances before they are distributed to the body
Many drugs may be metabolized before adequate plasma concentrations are reached
Distribution factors for drugs:
Process of moving drug trough circulatory system to target cells
Degree of distribution depends on physical/chemical properties of a drug, and its ability to penetrate cell membranes, capillaries, blood brain barrier
Solubility of drug: Water vs lipid solubility
Blood flow and if drug can pass blood brain barrier and have higher conc. in brain than skin
Capillary permeability (liver has high allowing drugs to flow through, brain does not)
Protein binding and binding profile will determine extend of drug distribution and elimination rate (only unbound drugs may diffuse thru cap., produce effect, metabolize, excrete)
What is the process of metabolism of a drug?
Process of oxidizing drugs into inactive products and conjugating them with new molecules to facilitate excretion
complex liver enzyme system converts lipid-soluble drugs to water metabolites that are easily eliminated by kidneys
Facilitated by cytochrome P450 microsomal enzyme system
-assist in detoxing of unusual chemicals
-find unusual molecules and adds oxygen atoms
making molecules more soluble in water and easier to
flush out the body (O2 also provides ready handle for
other detoxifying enzymes)
Phases of metabolism of a drug:
Phase I: oxidation- active compounds into inactive metabolite/ can also do reverse (occurs via cytochrome p450 system)
Phase II: conjugation- adds a polar molecule (ionizes) facilitates excretion of metabolites
What affects rates of metabolism?
blood flow, age, nutrition (albumin), liver integrity (enzyme prod.), genetics (enzyme prod.), polypharmacy (drug interaction), microbial flora
Process of excretion of drug metabolites:
Mostly renal but can be respiratory or thru skin, bile salts, feces
Good perfusion to kidneys will deliver more conjugated drug to the glomerulus and into filtrate
Low BP will mean little of the drug reaches glomerulus
Large molecules cannot pass thru glomerulus so protein bound drugs will not enter the filtrate; will remain in circulation
Damaged kidney will not be able to excrete drug products
Elimination drug factors:
Protein binding affinity
Degree of Ionization
-Ionized drugs tend to remain the circulating plasma which means that they will be delivered to glomerulus and excreted
-Non-ionized will move into cellular environments
Lipid or water soluble:
-lipid soluble drugs will tend to stay in cellular spaces and subcutaneous fat (less likely to perfuse to the kidney)
-tend to excrete more slowly than water soluble
-lipid soluble can be excreted thru lipid breast milk
Geriatric Considerations with Absorp., Dist., Metab., and Excretion?
Absorption- decreased cardiac output decreases blood flow to GI tract, decreasing drug absorption
Distribution- Decreased albumin production allows for higher levels of free drug increasing drug effects
Metabolism: Reduced hepatic enzyme activity and reduced hepatic blood flow reduced ability to metabolize drugs, leading to increased duration and effects of drugs
Excretion: Decreased renal function slows renal excretion of metabolites
Pediatric considerations:
age based variability in absorption, metabolism, distribution, excretion
weight must be used for calculating precise drug doses
Infants/children have decreased gastric pH
absorption rates of medications can very due to erratic blood flow
infants have higher rates of TBW and lower rates of fat can affect drugs that are more hydrophilic or lipophilic
What does steady state mean?
Drugs going in = Drugs going out
this take 4-5 half lives
organ disease or drug interaction can prolong half life
Genetics can also contribute
What is the difference between loading and maintenance dose?
Loading dose: able to achieve desired effects faster
Maintenance dose: longer onset for effects usually 4-5 doses before it reaches what a loading does can
What is a minimum effective drug dose?
amount of drug needed for desired effect
Therapeutic range and what do you use to calculate this?
Drug concentration between minimum effective dose and toxic concentration
What does pharmacodynamic’s mean?
What the drug does to the body
Study of biological and physiological effects of drugs and their mechanism of action
Interaction between drug and target cells or cells
Drug action within the body:
Drugs can change the environment of body cells (antacids neutralize stomach acidity)
Drugs can bind to receptors on cell membranes and create a signal transduction that will alter cellular physiology
What is Agonism? And how does it act?
Agonist is a drug that binds to a receptor and produces a physiologic effect by stimulating the receptor
What is antagonism? How does it work?
Drug that binds to a specific receptor and blocks other substances from stimulating the receptor/Do not activate the receptor though like agonist
What is affinity and how it affects drug effects?
Receptor shape
Best fit with receptor shape will have maximal effect hence greater affinity
What is selectivity? And how it affects drug effects?
Selectivity only means having one effect
Usually means less side effects
What is allosteric binding?
When drug binds next door changing the shape of the receptor allowing more of the natural compound to enter
Benzodiazepine
Drug effectiveness:
Dose response curve -relates drug dose and magnitude of drug effect
Drugs can have multiple effects
Drugs vary in effectiveness (different sites of action//different affinities for receptors)
Effectiveness is related to its safety (therapeutic index)
What is the efficacy and potency of a drug? Which one is more important?
Efficacy: magnitude of max response produced by drug
Potency: Comparing drugs, the more potent will produce therapeutic effect at lower dose
Efficacy more important than potency
Drug effects?
Therapeutic-response we hope to achieve
Side effect- develop tolerance
Adverse effects- any undesirable experience associated with use of a medicine
Schedules of Drugs:
Schedule I: Illegal substance- marijuana, heroin
Schedule II: high potancy for abuse- opioid
Scheduled III: moderate low potential for abuse- anabolic steroids, ketamine, codeine
Schedule IV: low potential for abuse- Benzos, muscle relaxants, tramadol
Schedule V: lower potential for abuse- cough supp.
How to categorize drugs:
Pharmacologic class: drugs that share similar characteristics in their mechanism of action
(beta blockers)
Therapeutic class: therapeutic use (ex:
antihypertensives)
