Nurses need to have knowledge about the actions and effects of medications
To safely and accurately administer medications nurses need to have an understanding of pharmacologic principles
Pharmacologic Principles
Drug Names
Chemical name
Describes the drug’s chemical composition and molecular structure
Generic name (nonproprietary name)
Name given by the United States Adopted Name Council
Trade name (proprietary name)
The drug has a registered trademark; use of the name restricted by the drug’s patent owner (usually the manufacturer)
Drug Names (cont'd)
Chemical name
(+/-)-2-(p-isobutylphenyl) propionic acid
Generic name
ibuprofen
Trade name
Motrin®, Advil®
Figure 2-1 The chemical, generic, and trade names for the common analgesic ibuprofen are listed next to the chemical structure of the drug.
Pharmacological Concepts: Classification
Classification- Nurses learn to categorize meds with similar characteristics by their class
Medication classification indicates the effect of the med on the body system, the symptom the med relieves, or the med’s desired effect (e.g. oral hypoglycemics)
Pharmacological Concepts: Classification
A medication may also be part of more than one class
Aspirin is an analgesic, antipyretic, anti-inflammatory, and anti-platelet
Pharmacological Concepts: Medication Forms
Medications are available in a variety of forms and preparations
The form of the med will determine its route of administration
Composition of med is designed to enhance its absorption & metabolism
Many meds are available in several forms
Medication Forms
Tablet
Capsule
Elixir
Enteric-coated
Suppository
Suspension
Transdermal patch
Pharmacologic Principles
Pharmaceutics
Pharmacokinetics
Pharmacodynamics
Pharmacotherapeutics
Pharmacognosy
Pharmaceutics
The study of how various drug forms influence pharmacokinetic and pharmacodynamic activities
Pharmacokinetics
• The study of what the body does to the drug
Absorption
Distribution
Metabolism
Excretion
Pharmacodynamics
• The study of what the drug does to the body
The mechanism of drug actions in living tissues
Figure 2-2 Phases of Drug Activity. (From McKenry LM, Salerno E: Mosby’s pharmacology in nursing—revised and updated, ed 21, St. Louis, 2003, Mosby.)
Pharmacotherapeutics
The use of drugs and the clinical indications for drugs to prevent and treat diseases
Pharmacognosy
The study of natural (plant and animal) drug sources
Pharmacokinetics: Absorption
The rate at which a drug leaves its site of administration, and the extent to which absorption occurs
Bioavailability
Bioequivalent
Factors That Affect Absorption
Administration route of the drug
Ability of Med to Dissolve
Food or fluids administered with the drug
Body Surface Area
Status of the absorptive surface
Rate of blood flow to the small intestine
Lipid Solubility of Med
Status of GI motility
Routes of Administration
A drug’s route of administration affects the rate and extent of absorption of that drug
Enteral (GI tract)
Parenteral
Topical
Enteral Route
Drug is absorbed into the systemic circulation through the oral or gastric mucosa, the small intestine, or rectum
Oral
Sublingual
Buccal
Rectal
First-Pass Effect
The metabolism of a drug and its passage from the liver into the circulation
A drug given via the oral route may be extensively metabolized by the liver before reaching the systemic circulation (high first-pass effect)
The same drug—given IV—bypasses the liver, preventing the first-pass effect from taking place, and more drug reaches the circulation
Box 2-1 Drug Routes and First-Pass Effects
Parenteral Route
Intravenous (fastest delivery into the blood circulation)
Intramuscular
Subcutaneous
Intradermal
Intrathecal
Intraarticular
Topical Route
Skin (including transdermal patches)
Eyes
Ears
Nose
Lungs (inhalation)
Vagina
Distribution
The transport of a drug in the body by the bloodstream to its site of action
Protein-binding
Water soluble vs. fat soluble
Blood-brain barrier
Areas of rapid distribution: heart, liver, kidneys, brain
Areas of slow distribution: muscle, skin, fat
Metabolism (Also Known As Biotransformation)
The biologic transformation of a drug into an inactive metabolite, a more soluble compound, or a more potent metabolite
Liver (main organ)
Kidneys
Lungs
Plasma
Intestinal mucosa
Metabolism/Biotransformation (cont'd)
Delayed drug metabolism results in:
Accumulation of drugs
Prolonged action of the drugs
Stimulating drug metabolism causes:
Diminished pharmacologic effects
Excretion
The elimination of drugs from the body
Kidneys (main organ)
Liver
Bowel
Biliary excretion
Enterohepatic circulation
1. You are caring for a client who has diabetes complicated by kidney disease. You will need to make a detailed assessment when administering medications because this client may experience problems with:
1. You are caring for a client who has diabetes complicated by kidney disease. You will need to make a detailed assessment when administering medications because this client may experience problems with:
A. Absorption
B. Biotransformation
C. Distribution
D. Excretion
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Pharmacodynamics
Study of the mechanism of drug actions in living tissue
Drug-induced alterations to normal physiologic function
Positive change-Therapeutic effect-Goal of therapy
Mechanism of Action
Ways in which a drug can produce a therapeutic effect
The effects that a particular drug has depends on the cells or organ targeted by the drug
Once the drug hits its “site of action” it can modify the rate at which a cell or tissue functions
Mechanism of Action
Receptor Interaction
Enzyme Interaction
Non-Specific Interaction
Receptor Interaction
Drug structure is essential
Involves the selective joining of drug molecule with a reactive site on the cell surface that elicits a biological effect
Receptor is the reactive site on a cell or tissue
Once the substance binds to and interacts with the receptor, a pharmacologic response is produced
Receptor Interaction
Affinity- degree to which a drug binds with a receptor
The drug with the best “fit” or affinity will elicit the best response
Drug can mimic body’s endogenous substances that normally bind to receptor site
Drugs that bind to receptors interact with receptors in different ways to either block or elicita response
Receptor Interaction
Agonist-Drug binds to receptor-there is a response (Adrenergic Agents)
Antagonist-drug binds to receptor-no response-prevents binding of agonists (Alpha & Beta Blockers)
Enzyme Interaction
Enzymes are substances that catalyze nearly every biochemical reaction in a cell
Drugs can interact with enzyme systems to alter a response
Inhibits action of enzymes-enzyme is “fooled” into binding to drug instead of target cell
Protects target cell from enzyme’s action (ACE Inhibitors)
Non-Specific Interaction
Not involving a receptor site or alteration in enzyme function
Main site of action is cell membrane or cellular process
Drugs will physically interfere or chemically alter cell process
Final product is altered causing defect or cell death
Cancer drugs, Antibiotics
The nurse is giving a medication that has a high first-pass effect. The physician has changed the route from IV to PO. The nurse expects the oral dose to be:
1. Higher because of the first-pass effect.
2. Lower because of the first-pass effect.
3. The same as the IV dose.
4. Unchanged.
. A patient is complaining of severe pain and has orders for morphine sulfate. The nurse knows that the route that would give the slowest pain relief would be which route?
1. IV
2. IM
3. SC
4. PO
Type of Medication Action
Therapeutic Effect
Side Effects
Adverse Effects
Toxic Effect
Idiosyncratic Reactions
Allergic Reaction
Medication Interactions
Iatrogenic Response
Therapeutic Effect
The expected or predictable physiological response a medication causes
A single med can have several therapeutic effects (Aspirin)
It is important for the nurse to know why med is being prescribed
Side Effects
Unintended secondary effects a medication predictably will cause
May be harmless or serious
If side effects are serious enough to negate the beneficial effect of meds therapeutic action, it may be D/C’d
People may stop taking medications because of the side effects
Adverse Effects
Undesirable response of a medication
Unexpected effects of drug not related to therapeutic effect
Must be reported to FDA
Can be a side effect or a harmful effect
Can be categorized as pharmacologic, idiosyncratic, hypersensitivity, or drug interaction
Adverse Effects
Adverse Drug Events
Adverse Drug Reactions (ADR)
Toxic Effect
May develop after prolonged intake or when a med accumulates in the blood because of impaired metabolism or excretion, or excessive amount taken
Toxic levels of opioids can cause resp.depression
Antidotes available to reverse effects
Idiosyncratic Reactions
Unpredictable effects-overreacts or under reacts to a medication or has a reaction different from normal
Genetically determined abnormal response
Idiosyncratic drug reactions are usually caused by abnormal levels of drug-metabolizing enzymes (deficiency or overabundance)
Allergic Reaction
Unpredictable response to a medication
Makes up greater than 10% of all medication reactions
Client may become sensitized immunologically to the initial dose, repeated administration causes an allergic response to the med, chemical preservative or a metabolite
Allergic Reaction
Medication acts as an antigen triggering the release of the body’s antibodies
2. A postoperative client is receiving morphine sulfate via a PCA. The nurse assesses that the client’s respirations are depressed. The effects of the morphine sulfate can be classified as:
2. A postoperative client is receiving morphine sulfate via a PCA. The nurse assesses that the client’s respirations are depressed. The effects of the morphine sulfate can be classified as:
A. Allergic
B. Idiosyncratic
C. Therapeutic
D. Toxic
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Other Drug Reactions
Teratogenic-Structural effect in unborn fetus (thalidomide)
Not always undesirable, physician may combine meds to create an interaction that will have beneficial effects (Vasodilators & diuretics to control high BP)
Medication Dose Responses
Except when administered IV, meds take time to enter bloodstream
The quantity & distribution of med in different body compartments change constantly
Goal is to keep constant blood level within a safe therapeutic range
Repeated doses are required to achieve a constant therapeutic concentration of a med because a portion of med is always being excreted
Medication Dose Responses
Serum Half-Life:Time it takes for excretion processes to lower the serum medication concentration by ½
Regular fixed doses must be given to maintain therapeutic concentration
Dosage schedules set by institutions (TID, q8h, HS, AC, STAT, PRN)
Peak & Trough levels
Therapeutic drug monitoring
Half-life
The time it takes for one half of the original amount of a drug in the body to be removed
A measure of the rate at which drugs are removed from the body
Onset, Peak, and Duration
Onset
The time it takes for the drug to elicit a therapeutic response
Peak
The time it takes for a drug to reach its maximum therapeutic response
Duration
The time a drug concentration is sufficient to elicit a therapeutic response
Pharmacotherapeutics: Types of Therapies
Acute therapy
Maintenance therapy
Supplemental therapy
Palliative therapy
Supportive therapy
Prophylactic therapy
Empiric therapy
Monitoring
The effectiveness of the drug therapy must be evaluated
One must be familiar with the drug’s:
Intended therapeutic action (beneficial)
Unintended but potential side effects (predictable, adverse reactions)
Monitoring (cont'd)
• Therapeutic index
– The ratio between a drug’s therapeutic benefits and its toxic effects
Involves the physician, nurse, nursing unit, pharmacy department, and patient education
Other “Rights”
Proper drug storage
Proper documentation
Accurate dosage calculation
Accurate dosage preparation
Careful checking of transcription of orders
Patient safety
Other “Rights” (cont'd)
Close consideration of special situations
Prevention and reporting of medication errors
Patient teaching
Monitoring for therapeutic effects, side effects, toxic effects
Refusal of medication
Evaluation
• Ongoing part of the nursing process
Determining the status of the goals and outcomes of care
Monitoring the patient’s response to drug therapy
Expected and unexpected responses
The day shift charge nurse is making rounds. A patient tells the nurse that the night shift nurse never gave him his medication, which was due at 11 PM. What should the nurse do first to determine whether the medication was given?
1. Call the night nurse at home.
2. Check the Medication Administration Record.
3. Call the pharmacy.
4. Review the nurse’s notes.
The patient’s Medication Administration Record lists two antiepileptic medications that are due at 0900, but the patient is NPO for a barium study. The nurse’s coworker suggests giving the medications via IV because the patient is NPO. What should the nurse do?
1. Give the medications PO with a small sip of water.
2. Give the medications via the IV route because the patient is NPO.
3. Hold the medications until after the test is completed.
4. Call the physician to clarify the instructions.
Life Span Considerations
Life Span Considerations
Pregnancy
Breast-feeding
Neonatal
Pediatric
Geriatric
Pregnancy
First trimester is the period of greatest danger for drug-induced developmental defects
Drugs diffuse across the placenta
FDA pregnancy safety categories
Table 3-1 Pregnancy safety categories
Breast-feeding
Breast-fed infants are at risk for exposure to drugs consumed by the mother
