Download Pharmacology 120

Pharmacology 120
Instructor
Susan Dolezal, R.N., M.S.
Introduction: Chapter 1
• Definition of Pharmacology: the study of drugs and their actions on living organisms
• Nurses need to have medication knowledge because nursing responsibilities include
the safe:
– Administration of drugs
– Assessment of effects of drugs
– Intervening to make drug regimens more tolerable
– Provision of patient teaching about drugs and the drug regimen
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Sources & Evaluation of Drugs
Drugs may come from plants (digoxin, opiates), animals (beef insulin), inorganic
compounds (iron & gold salts), or be produced synthetically (Humulin insulin).
The Food & Drug Administration (FDA) regulates the development & sale of drugs
The FDA had established five categories to indicate the potential for systemically
absorbed drugs to cause birth defects.
The FDA also determines the abuse potential of controlled substances, and has
established categories for ranking these drugs
Drug Approval Process
• FDA tightly controls drug testing, to evaluate the safety and effectiveness of new
drugs.
• Nurse Practice Acts - Every state has its own laws regarding drug administration by
nurses. Can get a copy.
• In a civil court, the nurse can be prosecuted for giving the wrong drug or dosage,
omitting a drug, or giving the drug by the wrong route.
Drug Names
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Each drug may have several names
Chemical Name - Describes the drug’s chemical structure (most meaningful to the
chemist)
Generic Name - Official name for the drug
- Not owned by any drug company
- Universally accepted (i.e. acetaminophen)
Brand/Trade Name - A registered trademark of a drug company, easier to
spell/pronounce (Tylenol) - Cardizem (brand) diltiazem HCL (generic)
Drug Approval: Pregnancy
• FDA developed a classification system related to the effects of drugs on unborn child
(fetus)
• In drug books and literature, pregnancy category is indicated for most drugs
- A - No risk to fetus based on studies
- B - Little to no risk based on animal studies,
some human studies
- C - Risk indicated based on animal studies. Evaluate risk vs. benefit .
- D - Risk to fetus proved. Risk vs. benefit to mother
- X - Risk proved. Avoid during pregnancy
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Controlled Substances Schedule
1970 - The Controlled Substance Act passed to remedy drug abuse/dependence.
Included scheduling of controlled drugs into classifications:
- CI - Illegal drugs (highest abuse potential – i.e. Heroin)
- CII - High potential for abuse (physical & psychological)
& dependency (narcotics, amphetamines, barbiturates)
- CIII - Combo drugs (Codeine preparations) High
potential for abuse/dependency
- CIV - Medium potential for abuse/dependence (anti-anxiety meds such as Valium)
- CV - Limited potential for abuse (Codeine cough syrup)
Over-The-Counter (OTC) Meds
• Over-the-counter (OTC) drugs are products that are available without a prescription
for self-treatment of various problems
– Many patients do not report use of OTC meds, as they do not consider them to be
“real medicines”; health care workers must ask about their use!
– OTC meds can still be dangerous if not taken correctly (limit on acetaminophen
dosing!), can interact with other medications, and can mask signs & symptoms of
underlying disease (headaches & HTN)
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Where To Get Information!
Physician’s Drug Reference (PDR)
Nursing Drug Handbooks
Internet Drug Sites: Drug Formulary at: http://www.intmed.mcw.edu/drug.html
Package inserts that come with new meds
The hospital pharmacist
24 hour Walgreen’s or Osco pharmacist!
(Be careful with the review questions/answers in the textbook - they aren’t all correct
for Chapter 1!)
Chapter 2: Drugs and the Body
• Definition of Pharmacology: the study of drugs and their actions on living organisms
• 3 Phases for drug action to occur:
• 1 – Pharmaceutic: how the drug gets into the body
• 2 – Pharmacokinetic: how the body acts on the drug
• 3 – Pharmacodynamic: how the drug affects the body
• * Please refer to the Terms & Definitions sheet attached to your syllabus!
Pharmacodynamics
Categories of Drug Action
4 categories of drug action: (example!):
• - replacement (insulin)
• - stimulation of cellular activities (Type II DM meds)
• - depression or slowing of cellular activities (SSRIs)
• - to interfere with the functioning of foreign cells, such as invading microorganisms or
neoplasms (chemotherapeutic agents: antibiotics and cancer medications)
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Pharmacodynamics
Receptor Theory
Most receptors are protein in structure and found on cell membranes
Drugs act through receptors either by binding to the receptor to produce a response
(agonist) (i.e. insulin letting glucose into the cell) or by blocking a response
(antagonist) (i.e. SSRIs block removal of serotonin from receptor sites – more
serotonin available to cell, less depression)
Almost all drugs lack specific and selective effects; those which are specific (such as
penicillin) are said to have selective toxicity.
These other effects may be desirable or harmful (i.e. cancer chemotherapy kills tumor
cells, but also causes hair loss & anemia)
Phase 1:
Pharmaceutic
Approximately 80% of drugs are taken by mouth and pharmaceutic (dissolution) is the
first phase of drug action. Oral administration is the cheapest & safest way to
administer drugs, but stomach acid may interfere – hence the use of binders which are
broken down at particular acidity levels, then releasing the active drug.
In GI tract - drugs need to be in solution to be absorbed
Solids (tablets, capsules) must disintegrate into small particles to dissolve into liquid
(dissolution)
Liquid drugs are already solutions
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Pharmaceutic
Disintegration - breakdown of the tablet into smaller particles
Dissolution - dissolving of the smaller particles in GI fluid before absorption
Rate limiting - time it takes the drug to disintegrate and dissolve to become available
for the body to absorb it
Pharmaceutic
Drugs dissolve faster in acidic environments
- Older adults/infants have less acid; slower absorption leads to toxicity (WHY?)
Enteric coated tablets do not disintegrate until reaching the alkaline environment of the
small intestine – (they are designed to do this) - DO NOT CRUSH them!
Phase 2:
Pharmacokinetics
The process of drug movement to achieve drug action
4 processes: Absorption, Distribution, Metabolism (Biotransformation), and Excretion
(elimination) - ADME
The nurse must be alert to any adverse drug effects and to report such findings
promptly
Critical concentration – the amount of drug needed to cause a therapeutic effect; may
use a loading dose to achieve more quickly
Phase 2:
Pharmacokinetics
Dynamic Equilibrium of drug concentration is affected by the 4 processes of
pharmacokinetics:
– Absorption – from the site of entry into the body
– Distribution – to the active site
– Metabolism (Biotransformation) – in the liver
– Excretion (elimination) – from the body
Pharmacokinetics: Absorption
Passage of drug from its site of administration into the blood/circulating body fluids
Rate of absorption depends on the route of administration: Enteral (via GI tract),
parenteral (injected), topical (through the skin), inhaled into the lungs, through mucous
membranes (sublingual, buccal)
Absorption
• Some drugs are absorbed into the small intestine via the extensive mucosal villi.
When is absorption compromised?
• Hydrochloric acid (which we all have in our stomachs!) destroys some drugs – so a
much larger oral dose must be given to offset the dosage loss. (Compared to dosage
of same med given IV or IM.)
• Ideally, (for consistent absorption) all oral drugs should be given 1 hour before or 2
hours after meals.
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Absorption
Bioavailability is a subcategory of absorption – it refers to the percentage of the
administered drug dose that reaches the systemic circulation
Occurs after absorption and hepatic drug metabolism
Oral route is always less than 100% - due to first- pass effect (next slide!)
Intravenous route is usually 100%
Absorption
• First Pass Effect: drugs that are taken orally are usually absorbed from the small
intestine directly into the portal venous system; the portal veins deliver these absorbed
molecules directly into the liver. In the liver, much of the drug becomes inactive & is
excreted. Some drugs, such as aspirin & alcohol, do not undergo metabolism in the
liver at all; they are absorbed into the body from the lower end of the stomach.
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Pharmacokinetics:
Distribution
The ways in which drugs are transported by the circulating body fluids to the sites of
action
Influenced by blood flow, affinity to the tissue, and protein binding effect
Drugs are distributed in the plasma (liquid part of the lymph and blood) and are bound
by varying degrees to protein (albumin)
Distribution
• Portion of drug bound to protein is inactive - not available to receptors; drug must be
freed from the protein’s binding site at the tissues.
• Portion of drug unbound is free, active
- only free drugs can cause a pharmacologic
response
- some circulating drugs (anticonvulsants, aminoglycosides) are checked for drug
blood levels
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Distribution
Need to be aware of the condition of your client - liver or kidney disease = low serum
albumin level = less protein-binding sites = excess free drug. What happens?
Remember - The amount of drug that actually reaches the receptor sites determines the
extent of pharmacologic activity
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Pharmacokinetics:
Metabolism or Biotransformation
Major mechanism of the termination/inactivation of drug action
Liver is primary site where drugs are inactivated by liver enzymes, becoming inactive
metabolites or water- soluble substances for excretion
Liver disease alters drug metabolism = drug toxicity d/t a decreased rate of metabolism
Pharmacokinetics:
Excretion
• Drug removal from the body
• Main route is through the urine
- other routes = bile, feces, lungs, breast
milk, skin, saliva
• Urine pH influences excretion
• Kidney disease affects excretion (like liver disease, leads to build up of drug and
toxicity)
• Half-life (t1/2) - the time it takes for 1/2 of a drug to be eliminated; after 5 half-lives,
>96% of drug is eliminated.
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Phase 3:
Pharmacodynamics
Def: How the drug affects the body
Drug response can cause a primary or secondary physiologic effect, or both
Primary effect = desirable
Secondary effect = desirable or undesirable (i.e. Benedryl –antihistamine >sleepy)
Pharmacodynamics
Onset, Peak, Duration
Onset of action = time it takes to reach the minimum effective concentration
Peak action = When the drug reaches its highest blood or plasma concentration
Duration of action = Length of time drug has an effect (this is where knowing the t ½
and the condition of the patient’s liver & kidneys comes in handy!)
Pharmacodynamics
Therapeutic Index/Range
Safety of drugs is a major concern
Therapeutic index - estimates the margin of safety of a drug
Low therapeutic index = narrow safety
High therapeutic index = wide safety margin, less danger of toxic effects
Therapeutic range = area between the minimum effective concentration & minimum
toxic concentration of a drug
Pharmacodynamics:
Factors Influencing Drug Effects
• Info in drug books is based on the reaction (to the drug) on a healthy, 150 # male!
• Weight: if < 150 #, normal dosage might prove toxic; if > 150#, normal dose might not
cause desired response
• Age: children need to have dosages converted appropriately. Older adults usually
need lower doses as well, due to decreased plasma proteins, & decreased liver &
kidney function.
Factors Influencing Drug Effects (cont.)
• Gender: males have more vascular muscles; so IM injections act more quickly in men
than women; women have more fat cells; so drugs deposited in fat (like gas
anesthetics) act much longer in women.
• Physiological factors: diurnal rhythm of the nervous & endocrine systems, acid-base
balance, & electrolyte balance all affect the way the drug works in each individual
• Pathological factors: i.e. GI disorders can affect the absorption of many oral drugs;
vascular diseases & low B/P affect the distribution of drugs: not enough “umph” to
get drug to tissues where it is needed. Liver & kidney disease:
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Factors Influencing Drug Effects (cont.)
Genetic factors: cultural differences due to differences in enzyme levels
Immunological factors: drug allergies
Psychological factors: placebo effect: drug works best when patient believes it will
work. Health beliefs (trust), & compliance with treatment
Environmental factors: heat & vasodilators for hypertension, sedating drugs & calm,
quiet environment
Factors Influencing Drug Effects (cont.)
• Tolerance: patient may develop tolerance to drugs over time, requiring larger dose to
achieve initial effect.
• Cumulation: if drug doses taken too close together, drug accumulates in the body,
leading to “overdosage” and toxic effects
• Drug-drug interactions: when two or more drugs are taken together, they can increase
of decrease the efficacy of one or both drugs. Can occur during all phases (ADME).
Check drug handbook.
• Drug-food interactions: i.e. tetracycline & milk
• Drug-laboratory interactions: i.e. change in liver enzymes