Essential Pharmacology and Medication Administration

Posted on Feb 19, 2026 in Medicine & Health

Essential Pharmacology Terms

  • Onset: The time it takes for a drug to reach the minimum effective concentration.
  • Peak drug level: The highest drug concentration in the blood.
  • Trough drug level: The lowest concentration reached before the next dose.
  • Duration: The length of time a drug exerts a therapeutic effect.
  • Side effects: Secondary drug effects.
  • Adverse reactions: Unintentional or unexpected reactions.
  • Drug interactions: A changed action of a drug resulting from interaction with another drug.
  • Drug toxicity: Occurs when drug levels exceed the therapeutic range.
  • Synergistic: Two drugs working together more effectively than one drug alone.
  • Agonist: A drug that produces a desired response.
  • Loading dose: A higher initial dose to reach therapeutic levels quickly.
  • Antagonistic: A drug that blocks a response.
  • Selective vs. Nonselective: Affecting a specific receptor versus multiple receptors.
  • Tolerance: When the body becomes accustomed to a medication over time, requiring higher doses for the same effect.
  • Generic name: The legal, noncommercial name (often derived from the chemical name); written in lowercase.
  • Trade name (Proprietary): The commercial name; multiple brands may exist for one generic drug; written in uppercase.

Drug-Nutrient and Environmental Interactions

Drug-Nutrient Interactions

Food may increase, decrease, or delay drug response. Examples include Tyramine and Grapefruit juice.

Drug-Induced Photosensitivity

A drug-induced skin reaction caused by exposure to sunlight.

Pharmacogenetics and Nursing Responsibilities

Pharmacogenetics is the study of how a patient’s genome affects drug response. This helps individualize treatment regimens to decrease adverse reactions and costs while increasing adherence.

  • Nursing Responsibility: Assess family history for drug reactions and assess ethnicity.

Complementary and Alternative Therapies

These include botanicals, nutritional products, and herbal supplements. They can interact with prescription and over-the-counter (OTC) drugs.

Medication Assessment

Always assess for: Prescription/OTC medications, herbal supplements, and alcohol or drug use.

Common Herbal Supplement Interactions

  • Garlic: Used for hypercholesterolemia, hypertension, and heart disease. Side Effects: Blood thinning, heartburn, upset stomach, and body odor.
  • Ginger: Used for nausea, motion sickness, and pain relief. Side Effects: Blood thinning, gas, bloating, and heartburn.
  • Ginkgo biloba: Used for asthma, fatigue, and memory improvement. Side Effects: Blood thinning, headache, dizziness, and GI upset.
  • Ginseng: Used for stamina and immune support. Side Effects: Blood thinning, headaches, GI distress, and hypoglycemia.
  • St. John’s Wort: Used for mental and sleep disorders. Side Effects: Anxiety, dry mouth, and photosensitivity. Note: Interacts with SSRIs and birth control; do not take with antidepressants.

Hazards of Herbal Use

  • Natural does not mean safe.
  • Herbs can affect lab results and interfere with surgery (stop 2–3 weeks prior).
  • Do not use if pregnant, nursing, or for infants without provider approval.

Safe Use of Over-the-Counter (OTC) Drugs

OTC drugs can be acquired without a prescription, but they can still be addictive or dangerous.

Advantages and Disadvantages

  • Advantages: Easy access, no prescription needed, treats minor ailments.
  • Disadvantages: Risk of overdose, potential to mask serious conditions, and unregulated by the FDA.

Management of Controlled Substances

Schedule 1 and 2 drugs require a DEA number to prescribe.

  • Ensure only authorized staff access medication.
  • Keep updated records and store opioids under double lock.
  • Ensure wasted substances are countersigned.
  • Diversion: A provider abusing controlled drugs in the workplace.

Pharmacokinetics: The Body’s Action on Drugs

Pharmacokinetics (PK) involves Absorption, Distribution, Metabolism, and Excretion (ADME).

1. Absorption

The movement of a drug from the site of administration to the bloodstream.

  • Disintegration: Breakdown of oral drugs in the stomach. Sustained Release (SR/ER/XR) and Enteric Coated (EC) drugs must not be crushed.
  • Dissolution: Combining drug particles with liquid for absorption.

2. Distribution

Movement of the drug to body tissues. Protein binding renders drugs inactive; only “free drugs” are active. Low albumin levels increase the risk of toxicity for highly protein-bound drugs.

3. Metabolism (Biotransformation)

Chemical alteration by the liver. Bioavailability is the amount of drug available for use. The First-pass effect occurs when PO drugs are metabolized by the liver before reaching systemic circulation.

4. Excretion

Elimination via kidneys, liver, lungs, and skin. Half-life (t½) is the time required for half the drug to be removed. A Steady state is reached after approximately 4–5 half-lives.

Pharmacodynamics: The Drug’s Action on the Body

  • Therapeutic Index (TI): The difference between a therapeutic and toxic dose. Narrow TI drugs (e.g., Warfarin, Digoxin) require frequent monitoring.
  • Therapeutic Drug Monitoring: Ensures safety, especially for antibiotics like Gentamicin and Vancomycin.

Geriatric Pharmacotherapy Considerations

Aging leads to decreased blood flow, albumin, and organ function, resulting in reduced ADME.

  • Polypharmacy: Use the Beers Criteria to identify potentially inappropriate medications (PIMs).
  • Adherence: Nonadherence can lead to underdosing or overdosing.
  • Teaching: Use large print, face the patient, and ensure they have functional hearing aids/glasses.

Substance Use Disorders and Patient Care

Alcohol Toxicity

Monitor for withdrawal (tremors, anxiety, seizures, or delirium tremens) 6 hours to 5 days after the last drink. Use the Alcohol Withdrawal Scale (AWS).

Tobacco Use Disorder

Withdrawal symptoms include cravings, irritability, and increased appetite. Treatments include Cognitive Behavioral Therapy and Bupropion.

Pain Management in SUD

Treat patients with dignity; pain management is a higher priority than the substance use disorder itself.

Safe Medication Disposal Procedures

  • At Home: Mix drugs with undesirable substances (e.g., kitty litter), seal in a bag, and remove labels. Do not flush unless instructed.
  • In Hospital: Use specialized containers and follow facility policy for IV bags.

National Patient Safety Goals and the Six Rights

The Joint Commission (TJC) established standards for abbreviations and Black Box Warnings for serious hazards.

The Six Rights of Medication Administration

  1. Right Patient: Use two forms of ID and scan barcodes.
  2. Right Drug: Read labels three times and check the HCP prescription.
  3. Right Dose: Validate calculations; high-alert drugs (Insulin/Heparin) require 2 RNs.
  4. Right Time: Follow agency policy and check expiration dates.
  5. Right Route: Assess swallowing ability and use aseptic technique.
  6. Right Documentation: Record administration immediately.

Clinical Routes of Drug Administration

  • Eye Drops: Apply to the middle third of the conjunctival sac; apply pressure to the lacrimal duct.
  • Ear Drops: Pull ear down and back for children under 3; up and back for those over 3.
  • Nasal Sprays: Aim toward the eye while the patient looks down.
  • NG/G-Tubes: Check placement (pH test) and residual (stop if >100 mL). Flush before, between, and after meds.
  • Parenteral:
    • IM: 90° (Ventrogluteal, Deltoid, Vastus Lateralis).
    • SQ: 45° (Abdomen, thigh, upper arm).
    • IV: 25°.
  • Z-Track Method: Used for irritating medications (e.g., Iron). Pull skin to the side, inject, wait 10 seconds, and release.