Effectiveness: This is the most important property a drug can have. It implies that the drug elicits the response for which it is given.
Safety: A safe drug is defined as one that cannot produce harmful effects—even if administered in very high doses and for a very long time. It is important to note that all drugs have the ability to cause injury, especially with high doses and prolonged use.
Selectivity: A selective drug is defined as one that elicits only the response for which it is given. There is no such thing as a wholly selective drug because all drugs cause side effects.
Reversible Action: For most drugs, it is important that effects be reversible (e.g., general anesthetics must wear off).
Predictability: It is helpful to know with certainty how a given patient will respond to a particular drug, though every patient is unique.
Ease of Administration: An ideal drug should be simple to administer. This can enhance patient adherence and decrease risk of administration errors.
Freedom from Drug Interactions: When a patient is taking multiple drugs, these agents can interact. An ideal drug would not interact with other agents.
Low Cost: An ideal drug would be easy to afford.
Chemical Stability: Some drugs lose effectiveness during storage or when put into solution; an ideal drug retains activity.
Possession of a Simple Generic Name: Generic names are often complex and difficult to remember; a simple name is preferable.
Therapeutic Objective and Response Factors
Therapeutic Objective/Goal: The ultimate objective of drug therapy is to provide maximum benefit with minimum harm.
Factors Determining Intensity of Drug Responses:
Administration: Dosage size, route, and timing are important determinants of drug responses. Toxicity can occur if dosage is too high; treatment failure occurs if it is too low.
Pharmacokinetics: Processes that determine how much of an administered dose gets to its sites of action. The four major processes are absorption, distribution, metabolism, and excretion.
Pharmacodynamics: The impact of drugs on the body. Once a drug has reached its site of action, pharmacodynamic processes determine the nature and intensity of the response.
Sources of Individual Variation: Physiological variables (age, gender, weight), Pathological variables (kidney/liver function), and Genetic variables.
Application of Pharmacology in Nursing Practice
Drug Cards to Know:
Acetaminophen
Ibuprofen
Pre-administration Assessment:
Collecting Baseline Data: Needed to evaluate therapeutic and adverse responses.
Identifying High-Risk Patients: Factors include liver/kidney impairment, genetic factors, drug allergies, pregnancy, and pediatric/elderly age groups.
Dosage and Administration:
Different indications may require different dosages.
Dosages may differ depending on the route of administration.
Guideline Steps for Correct Administration:
Check the medication order.
Verify the identity of the patient (e.g., using wristbands or asking for name/DOB).
Read the medication label.
Verify dosage calculations.
Implement any special handling the drug may require.
Critical Safety Rule: Do not administer any drug if you do not understand the reason for its use!
Nursing Responsibilities:
Promoting therapeutic effects.
Minimizing adverse effects and adverse interactions.
Making PRN (pro re nata) decisions.
Evaluating responses to medications.
Managing toxicity.
Patient Education:
Nurses must educate patients on the drug name, dosage, schedule, adherence, technique of administration (e.g., injection, inhaler), duration of use, and drug storage.
New Drug Development and Naming
The Randomized Controlled Trial (RCT):
Use of Controls: Comparing new drugs with standard drugs or placebos.
Randomization: Subjects are assigned randomly to groups to prevent bias.
Blinding: People involved do not know which group is receiving the drug or placebo (single or double-blind).
Stages of New Drug Development:
Pre-clinical Testing: Conducted in animals to assess toxicity, pharmacokinetics, and useful effects.
Clinical Testing:
Phase I: Conducted in healthy volunteers to evaluate metabolism, pharmacokinetics, and biologic effects.
Phases II and III: Conducted in patients to determine therapeutic effects, dosage range, safety, and effectiveness.
Phase IV: Post-marketing Surveillance: The drug is released for general use, allowing for the observation of effects in a large population.
Limitations of Testing:
There is historically limited information on women and children.
Testing fails to detect all adverse effects before a drug is marketed.
Drug Names:
Chemical Name: Description of the drug using the nomenclature of chemistry.
Generic Name: Assigned by the U.S. Adopted Names Council; each drug has only one generic name (nonproprietary name).
Brand Name: Proprietary or trade names under which the drug is marketed. One drug may have many brand names.
Generic vs. Brand Name: Generic products are generally preferred and contain the same dose of the same drug, but rates of absorption may differ between formulations.
Pharmacokinetics
Drug Cards to Know:
Warfarin
Nitroglycerin
Passing Membranes: Drugs must cross cell membranes through channels/pores, transport systems (e.g., P-glycoprotein), or direct penetration (most common, requires lipid solubility).
Absorption Routes:
Intravenous (IV): No barriers to absorption; instantaneous absorption. Advantages include rapid onset and control; disadvantages include cost, irreversibility, and risk of fluid overload or infection.
Intramuscular (IM) / Subcutaneous (SubQ): Barrier is the capillary wall. Absorption is rapid with water-soluble drugs and slow with poorly soluble ones.
Oral (PO): Barriers include the GI epithelium and capillary wall. Absorption is highly variable. Advantages include safety and convenience; disadvantages include inactivation by digestive enzymes/liver and patient requirements (conscious/cooperative).
Pharmaceutical Preparations (Oral):
Tablets: Compressed drug mix.
Enteric-Coated: Dissolve in the intestine, not the stomach.
Sustained-Release: Capsules filled with spheres that dissolve at different rates to release drug steadily.
Distribution:
Blood-Brain Barrier (BBB): Only lipid-soluble drugs or those with a transport system can cross.
Placental Drug Transfer: Not an absolute barrier; lipid-soluble non-ionized drugs pass easily.
Protein Binding: Many drugs bind to albumin. Bound molecules cannot leave the bloodstream.
Metabolism (Biotransformation):
Primarily occurs in the liver via hepatic drug-metabolizing enzymes (P450 system).
First-Pass Effect: Rapid hepatic inactivation of certain oral drugs before they reach systemic circulation.
Prodrugs: Inactive compounds that become active through metabolism.
Excretion:
Renal: Glomerular filtration, Passive tubular reabsorption, and Active tubular secretion.
Factors affecting renal excretion: pH-dependent ionization and competition for active transport.
Non-renal: Breast milk, bile, sweat, saliva, and expired air.
Time Course of Responses:
Minimum Effective Concentration (MEC): The plasma drug level below which therapeutic effects will not occur.
Toxic Concentration: Plasma level at which toxic effects begin.
Therapeutic Range: The range between the MEC and toxic concentration.
Half-Life (t1/2): The time required for the amount of drug in the body to decrease by 50%.
Plateau (Steady State): Reached when the amount of drug eliminated between doses equals the amount administered. It takes approximately four half-lives to reach a plateau.
Loading Dose: Large initial dose used to reach plateau quickly for drugs with long half-lives.
Complementary and Alternative Therapy (Chapter 86)
Dietary Supplement Health and Education Act of 1994 (DSHEA):
Categorizes botanical products, vitamins, and minerals as "dietary supplements" rather than drugs.
Exempts products from FDA scrutiny and approval before marketing.
Manufacturers do not need to prove safety or efficacy; the FDA must prove a product is unsafe to intervene.
Key Herbs and Supplements (* denotes increased bleeding risk):
Black cohosh: Used for menopause symptoms (hot flashes, vaginal dryness, depression).
Butterbur: Used for migraines, allergies, and asthma; has anti-inflammatory and vasodilatory effects.
Feverfew(increases bleeding risk): Suppresses arachidonic acid release and platelet aggregation. Used for migraine prophylaxis and immune disorders. Must discontinue 2 weeks before surgery.
Ginkgo biloba(increases bleeding risk): Used for memory, dementia, and intermittent claudication. Use caution with anticoagulants.
Echinacea: Used to stimulate immune function and treat viral infections.
St. John’s wort: Used for mild to moderate depression.
Garlic(increases bleeding risk): Used for cardiovascular effects (lower BP, lower LDL/triglycerides, higher HDL) and suppressing platelet aggregation.
Cranberry Juice(increases bleeding risk if taking warfarin): Used to prevent UTIs by preventing bacteria from adhering to the urinary tract wall.
Ginger Root(increases bleeding risk): Inhibits thromboxane production to suppress platelet aggregation. Used for vertigo and nausea/vomiting.
Green Tea: Used for weight loss, mental clarity, and cancer prevention.
Saw Palmetto: Used to relieve urinary symptoms of Benign Prostatic Hyperplasia (BPH).
Neuropharmacology and Adrenergic/Muscarinic Drugs
Basic Principles: Understanding the physiology of the Peripheral Nervous System (PNS).