CNO Practice Standard: Medication
Safe, effective, and ethical administration |
Knowledge, technical skill, and judgement required |
Ongoing maintenance of competence |
Evaluation
Systematic, ongoing, and dynamic part of the nursing process |
Determining status of goals and outcomes of care |
Monitoring patient's response to drug therapy (Therapeutic, expected, toxic responses) |
Clear, concise documentation |
Drug Absorption of Various Oral Preparations
Fastest |
Liquids, elixirs, syrups |
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Suspension solution |
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Powders |
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Capsules |
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Tablets |
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Coated tablets |
Slowest |
Enteric-coated tablets |
Pharmacokinetic Phase: First-pass effect
The metabolism of a drug and its passage from liver into circulation |
Oral drugs are absorbed from intestinal lumen into mesenteric blood system, and go to the liver by means of portal vein |
Once in the liver, it is metabolized by P450 enzyme system and passed into general circulation |
If large amount of drug is metabolized to an inactive form, then less is available in circulation (high first-pass effect) |
Means that most drugs have bioavailability of <100%, whereas same drug given IV is 100% bioavailable because it has not been metabolized by the liver |
- A drug given via oral route may be extensively metabolized by the liver before reaching systemic circulation (high-pass effect)
- Same drug given IV bypasses liver, preventing the first-pass effect from taking place, and more drug reaches circulation
- ie. Nitro
Drugs and Children
<38 weeks gestation |
Premature or preterm infant |
<1 month |
Neonate or newborn infant |
1month - 11months |
infant |
1 year - 12 years |
Child |
13 years - 19 years |
Adolescent |
Important to weigh in kg as doses often weight and/or body surface area based |
Drugs and Breastfeeding
Many drugs pass into breast milk |
Lower than in maternal circulation |
Depends on drug properties (lipid solubility, concentration, etc.) |
Must consider the harm-benefit ratio |
Pharmacotherapeutics: Nursing responsibility
Assessment:
- Current medication
- Pregnancy
- Breast feeding
- Concurrent illnesses
- Allergies/sensitivities
- Contraindications: Make the use of the drug very dangerous
Implementation:
- Intent of the therapy, as well as the psycho-motor skill of administering
- Acute therapy
- Maintenance therapy
- Supplemental therapy
- Palliative therapy
- Prophylactic therapy
Monitoring:
- Client's condition
- Side effects (predictable)
- Adverse effects/reaction (serious)
- Toxic effects
- Interactions
Evaluation:
Reassessing client's condition and therapeutic effectiveness of pharacotherapy |
Interactions - Alteration of drug action by:
- Other prescribed drugs
- Over-the-counter medications
- Herbal therapies
- Food or alcohol interactions
Pharmacodynamics: Mechanism of Action
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Receptor Interaction Drug reacts with a site on the surface of a cell or tissue to elicit/block a physiological response
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Receptor agonist Elicit response from the cell
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Receptor antagonist Do not elicit response (block usual physiological response)
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Enzyme interaction Drug inhibits/alters physiological response of enzyme; fools cell to attach to it VS its targeted cells
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Non-specific interaction Drugs interfere with or chemically alter cellular/metabolic processes
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Drugs produce their actions through 1 of 3 primary mechanisms of action: Receptors, enzymes or non-specific interaction
Receptor Interaction: Drugs will have affinity to bind to particular receptor – good fit and strong affinity means greatest response
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Pharmacological Principles
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Pharmaceutics Science of preparing and dispensing drugs, including dosage form and design (ie. Tablets, patches, capsules, injections)
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Pharmacokinetics What the body does to the drug (Absorption, distribution, metabolism, excretion)
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Pharmacodynamics What the drug does to the body (biochemical and physiological interactions)
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Pharmacotherapeutics Use of drugs and clinical indications for drugs to prevent and treat disease
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Pharmacognosy Study of natural plant and animal drug sources
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Phases of Drug Activity
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I. Pharmaceutical Phase Disintegration of dosage form
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II. Pharmacokinetic Phase Absorption, distribution, metabolism, excretion
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III. Pharmacodynamic Phase Drug-receptor interaction
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Pharmaceutical phase - becomes available for absorption once administered
Pharmacokinetic phase - drug is being manipulated by body and becoming available for action
Pharmacodynamic phase - drug having desired effect on target
Pharmaceutical Phase
Solutions absorbed faster than solids
Absorbed faster in acidic fluids than alkaline fluids
Young and elderly have less gastric acidity - drug absorption is generally slower
Food may increase/decrease absorption
Drugs and the Older adult
65 years or older |
Polypharmacy
Consumes 20-40% of Rx drugs, 40% OTC drugs |
Risk of drug interactions |
Refer to table 4.4 p. 68-69 for problematic drugs |
Drugs and Pregnancy
First trimester generally period of greatest danger |
Transfer to fetus primarily by diffusion across placenta and some active transport |
Factors that contribute to safety include drug properties, gestational age, and maternal factors |
Prescription Drugs
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Food and Drug Regulations (Schedule F) Lists drugs that must be sold by prescription
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Pharmacokinetics Phase: Elimination
Elimination of drugs from body |
Excrete through kidney (main organ) |
Other routes: liver, bile feces, lungs, saliva, sweat, breast milk |
Whether active or inactive metabolites, all the waste products have to be eliminated
Pharmacokinetics Phase: Metabolism
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Biotransformation: Primarily Liver (also skeletal muscle, kidney, plasma, lungs) Process of transforming a drug into inactive metabolite (more soluble compound)
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Cytochrome P-450 enzymes most responsible for biotransformation |
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Hepatic biotransformation varies (genetics, diseases, other drugs, etc.) |
Delayed drug metabolism results in accumulation of drugs in system - prolonged action time
Pharmacokinetic Phase: Distribution
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Distribution Drugs are distributed throughout body by blood stream
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Distribution influenced by:
- Blood flow
- Affinity to tissues
- Protein-binding (if drug binds to protein, they're less likely to be able to leave circulatory system, therefore not reach target tissue. Higher protein-binding of drug = slower its action will be. Albumin is most common blood protein drugs bind to. Portion of drug that is unbound and active is the "free" drug. Free drug increases risk of toxicity)
- Volume of drug distribution
Pharmacokinetic Phase: Absorption
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Absorption Process of drug leaving the site of administration and becoming available
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bioavailability speaks to extent of drug that is actually absorbed in blood stream
Factors that affect absorption:
Most oral drugs absorbed in small intestine
- Administration route of drug
- Food or fluids administered with drug
- Dosage formulation
- Status of absorptive surface
- Rate of blood flow to small intestines
- Acidity of stomach
- Status of GI motility
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10 Rights of Medications
Right drug |
Right dose |
Right time |
Right route |
Right patient |
Right reason |
Right documentation |
Right evaluation |
Right patient education |
Right to refuse |
Drug Names
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Chemical Name Drug's chemical composition and molecular structure
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Generic Name Name given by Health Canada under FDA and FDR
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Trade name Drug has registered trademark; use of name restricted by drug's patent owner
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Pharmacokinetic Phase: bypassing the liver
Sublingual |
Buccal |
Rectal |
Intravenous |
Intranasal |
Transdermal |
Vaginal |
Intramuscular |
Subcutaneous |
Inhalation |
- Routes do not require absorption within GI tract, therefore bypassing the liver and do not experience effect of "first-pass effect:
- Rectal route undergoes higher degree of first-pass effects than other routes listed
Pharmacokinetics: Half-life of a Drug
Time it takes for one half of the original amount of a drug to be eliminated from the body |
Metabolism and elimination affect the half-life of a drug |
Useful for determining 'steady state' |
After ~5 half-lives, most drugs are considered to be removed from the body (97%)
Pharmacokinetics: Steady-State
Amount of drug eliminated is equal to amount absorbed at each administration |
Steady-state is desired to achieve a therapeutic effect over time |
Longer half-life = longer it takes to reach steady state |
Pharmacokinetics: Onset, peak, duration
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Onset Time it takes to reach minimum effective concentration
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Peak Occurs when drug reaches highest blood or plasma concentration
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Duration Length of time drug has a pharmacologic effect
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Other Drug-Related Effects
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Teratogenic Disturb fetal/embryo development
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Mutagenic Changes genetic material
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Carcinogenic Cancer-causing
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Drug Legislation
Food and Drugs Act |
- Protect consumer from drugs that are contaminated, adulterated, or unsafe for use.
- Addresses drugs taht are labeled falsely and those with misleading/deceptive labels |
Controlled Drugs and Substances Act |
- Addresses possession, sale, manufacture, disposal, production, import, export, and distribution of certain drugs |
Over-the-Counter Drugs (OTC)
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Restricted Access Drug - Must ask pharmacist (insulin, loperamide)
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Pharmacy Only ie. Antihistamines, ulcer meds
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General Retail ie. Acetaminophen, nicotine gum
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Criteria for OTC Status - Consumer must easily diagnose condition and monitor effectiveness
- Drug should have: favourable adverse affect, profile, limited drug interaction profile, low misuse potentional
- Drug should be easy to use and easy to monitor
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