Handout on Pharmacology, Therapeutics, and Pharmacovigilance I (RGN 217) for Nursing Students

Introduction to Pharmacology, Therapeutics, and Pharmacovigilance

Pharmacology is the branch of medicine concerned with the effects of drugs on living organisms. It covers the entire journey of a drug, from its discovery and sources to its administration, mechanism of action, and elimination from the body. Pharmacology is essential for nurses because they are directly involved in drug administration, patient monitoring, and ensuring the safe and effective use of medications.

Therapeutics is the use of drugs to diagnose, prevent, or treat diseases. It involves the careful selection of medicines based on their effectiveness and safety profile. Lastly, pharmacovigilance plays a critical role in monitoring the safety of medicines and vaccines post-marketing. This handout covers these topics extensively, equipping students with the knowledge needed to apply pharmacological principles in their nursing practice, with a focus on drug safety monitoring as outlined by the Ghana Nurses and Midwifery Council (NMC) Curriculum.

1. Sources of Medicines

Medicines are derived from various natural and synthetic sources. The origin of a drug often determines its mechanism of action, composition, and safety profile. Understanding the different sources of medicines allows nurses to appreciate the complexity and diversity of therapeutic agents.

a. Plant-Based Medicines

Plants have been used as a primary source of medicines for thousands of years. Many modern drugs have origins in traditional herbal medicine. These medicines can be extracted directly from plants or synthesized to mimic plant compounds.

• Examples:
  • Quinine from the bark of the cinchona tree is used to treat malaria.
  • Morphine is extracted from the opium poppy and is used as a potent painkiller.
  • Digoxin, derived from the foxglove plant, is used to treat heart conditions.

Plant-based medicines can vary in potency depending on how they are processed, and they may also have side effects related to other compounds within the plant.

b. Animal-Based Medicines

Historically, animal tissues and secretions were used to create medicines. Even today, certain drugs are derived from animal sources, particularly hormones and enzymes.

• Examples:
  • Insulin: Originally derived from the pancreas of pigs and cows, insulin is now synthesized or produced using recombinant DNA technology to treat diabetes.
  • Heparin: A natural anticoagulant extracted from pig intestines, used to prevent blood clots in surgery and dialysis patients.

Animal-derived medicines have paved the way for synthetic alternatives, but some remain vital in modern medical treatments.

c. Synthetic Medicines

With advances in chemistry and biology, many drugs are synthesized in laboratories. Synthetic medicines are designed to mimic natural compounds or produce entirely new drugs with enhanced efficacy and reduced side effects.

• Examples:
  • Ibuprofen is a synthetic non-steroidal anti-inflammatory drug (NSAID) that provides pain relief and reduces inflammation.
  • Atorvastatin, a synthetic drug, is used to lower cholesterol levels in patients with cardiovascular risk factors.

Synthetic drugs have the advantage of being produced in controlled environments, ensuring uniformity in dosage and potency.

d. Bacterial and Fungal Sources

Certain microorganisms produce compounds that can inhibit the growth of other microbes. These natural products have led to the development of antibiotics.

• Examples:
  • Penicillin, discovered by Alexander Fleming from the fungus Penicillium, was the first antibiotic used to treat bacterial infections.
  • Streptomycin, derived from the bacterium Streptomyces griseus, is used to treat tuberculosis.

2. General Principles of Pharmacology: Pharmacokinetics and Pharmacodynamics

Pharmacology is divided into two fundamental principles: pharmacokinetics and pharmacodynamics. Understanding these principles is essential for nurses to administer medications safely and effectively, ensuring that patients receive the correct dose and benefit from the intended effects of the drug.

a. Pharmacokinetics: ADME Process

Pharmacokinetics describes the movement of drugs through the body, including absorption, distribution, metabolism, and elimination (ADME). Each phase is critical in determining the concentration of the drug at the target site and its overall efficacy.

i. Absorption

Absorption refers to how a drug enters the bloodstream after administration. The route of administration (oral, intravenous, intramuscular, etc.) affects the rate and extent of absorption.

• Factors Affecting Absorption:
  • Route of Administration: Drugs given intravenously bypass the absorption phase, while oral drugs must pass through the digestive system, where they may be broken down by stomach acid or enzymes.
  • Solubility of the Drug: Water-soluble drugs are absorbed more quickly than fat-soluble drugs, which need to cross cell membranes.

Nursing Considerations:

• Administer medications according to the prescribed route to maximize absorption. For example, some drugs may need to be taken with food to enhance absorption or to avoid stomach irritation.

ii. Distribution

Once absorbed, the drug is distributed throughout the body via the bloodstream. Some drugs bind to proteins (like albumin) in the blood, affecting their distribution to tissues.

• Factors Influencing Distribution:
  • Blood Flow to Tissues: Highly vascular organs like the brain, heart, and liver receive drugs more quickly.
  • Protein Binding: Drugs that are bound to plasma proteins are not active; only unbound drugs can exert a therapeutic effect.

Nursing Considerations:

• Be aware that certain conditions, such as liver disease, may reduce the body’s ability to distribute drugs effectively, leading to higher active drug levels and possible toxicity.

iii. Metabolism (Biotransformation)

Drugs are metabolized (broken down) primarily in the liver. The liver enzymes, particularly the cytochrome P450 system, convert drugs into more water-soluble forms for easier elimination.

• First-Pass Effect: Oral drugs are metabolized in the liver before reaching systemic circulation, reducing the amount of active drug available.

Nursing Considerations:

• Monitor liver function tests (LFTs) in patients on long-term medications, as impaired liver function can lead to drug accumulation and toxicity.

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iv. Elimination (Excretion)

Drugs and their metabolites are excreted from the body, primarily through the kidneys (in urine) or via bile, sweat, or exhalation.

• Renal Excretion: The kidneys filter out water-soluble drugs for excretion in the urine.
• Other Excretion Routes: Some drugs are excreted through bile (into the feces), or through sweat or exhalation (e.g., volatile anesthetics).

Nursing Considerations:

• Monitor kidney function in patients with renal impairment to prevent drug accumulation. This may involve adjusting dosages or selecting alternative medications.

b. Pharmacodynamics: How Drugs Work in the Body

Pharmacodynamics focuses on how drugs interact with receptors in the body to produce their effects. Drugs may stimulate or inhibit normal physiological processes, depending on their mechanism of action.

i. Drug-Receptor Interaction

Most drugs work by binding to specific receptors on cells to either initiate a response (agonists) or block a response (antagonists). For example, beta-blockers like propranolol block beta receptors to reduce heart rate and blood pressure.

ii. Dose-Response Relationship

This describes the relationship between the dose of a drug and the magnitude of its effect. Higher doses usually produce greater effects, but only up to a certain point. The therapeutic window is the range of drug doses that produce therapeutic effects without causing toxic effects.

iii. Therapeutic Index

The therapeutic index (TI) is a measure of a drug’s safety. It is the ratio of the drug’s toxic dose to its effective dose. Drugs with a narrow therapeutic index (e.g., digoxin) require careful monitoring to avoid toxicity.

Nursing Considerations:

• Ensure that drugs are administered within their therapeutic range, and monitor for signs of toxicity, particularly in drugs with a narrow therapeutic index.

3. Nursing Responsibilities in Administering Medicines

Administering medications is one of the core duties of nurses. It requires attention to detail, critical thinking, and knowledge of pharmacology to ensure patient safety and therapeutic effectiveness. Errors in medication administration can lead to severe consequences, including overdose, drug interactions, and adverse reactions.

a. The Five “Rights” of Medication Administration

The five “rights” provide a framework to ensure safe and accurate medication administration:

1. Right Patient: Always verify the patient’s identity using at least two identifiers (e.g., name and date of birth).
2. Right Drug: Ensure that the correct medication is administered, checking the drug name and dosage against the prescription.
3. Right Dose: Administer the exact dose as prescribed. Be cautious with high-alert medications that have a narrow therapeutic window.
4. Right Route: Administer the drug via the correct route (oral, IV, IM, subcutaneous, etc.).
5. Right Time: Give medications at the correct time intervals, considering drug half-life and interactions with meals or other medications.

Additional Rights:

• Right Documentation: Record the administration of the drug accurately and immediately after giving the medication.
• Right Reason: Ensure the medication is appropriate for the patient’s condition.

b. Analgesics

Analgesics are medications specifically designed to relieve pain. Understanding the different classes of analgesics and their mechanisms is crucial for effective pain management.

i. Opiates (e.g., Morphine, Pethidine)

• Mechanism of Action: Opiates bind to opioid receptors in the brain and spinal cord, blocking the transmission of pain signals and altering the perception of pain.
• Nursing Responsibilities:
  • Monitor for respiratory depression, especially in opioid-naïve patients or those with underlying respiratory issues.
  • Assess pain levels regularly using standardized pain scales.
  • Educate patients on the potential for dependence and the importance of adhering to prescribed dosages.

ii. Salicylates (e.g., Aspirin)

• Mechanism of Action: Salicylates inhibit cyclooxygenase (COX) enzymes, which are responsible for the formation of prostaglandins that mediate pain and inflammation.
• Nursing Responsibilities:
  • Assess for gastrointestinal irritation and bleeding, as aspirin can cause gastric ulcers.
  • Ensure patients understand the importance of taking aspirin with food to minimize GI discomfort.

iii. Non-Steroidal Anti-Inflammatory Agents (NSAIDs)

• Examples: Ibuprofen and diclofenac.
• Mechanism of Action: Like salicylates, NSAIDs inhibit COX enzymes, providing pain relief and reducing inflammation.
• Nursing Responsibilities:
  • Monitor for signs of renal impairment and GI bleeding.
  • Educate patients on the importance of not exceeding recommended dosages.

iv. Miscellaneous Analgesics (e.g., Paracetamol)

• Mechanism of Action: The exact mechanism is not fully understood, but paracetamol is believed to inhibit COX enzymes in the brain.
• Nursing Responsibilities:
  • Monitor for liver function, as excessive use can lead to hepatotoxicity.
  • Educate patients on recognizing signs of overdose, such as nausea, vomiting, and abdominal pain.

c. Hypnotics and Sedatives

These medications are used to induce sleep and reduce anxiety. Understanding their use is crucial for managing patients with insomnia or anxiety disorders.

i. Diazepam and Barbiturates

• Mechanism of Action: These drugs enhance the effects of the neurotransmitter gamma-aminobutyric acid (GABA), producing a calming effect on the brain.
• Nursing Responsibilities:
  • Monitor for excessive sedation and respiratory depression.
  • Educate patients about the potential for dependency and the importance of not abruptly discontinuing use.

4. Medicines Used in Infections

The management of infections often requires the use of antibacterial, antifungal, and antiviral medications. Nurses must understand the different classes of these drugs and their appropriate uses.

a. Antibacterial Medicines

Antibiotics are classified based on their mechanism of action and spectrum of activity. Understanding these classifications is vital for effective treatment of infections.

i. Penicillins (e.g., Benzylpenicillin, Amoxicillin, Cloxacillin)

• Mechanism of Action: Penicillins inhibit bacterial cell wall synthesis, leading to cell lysis.
• Nursing Responsibilities:
  • Monitor for allergic reactions, including anaphylaxis.
  • Ensure patients understand the importance of completing the full course of antibiotics.

ii. Aminoglycosides (e.g., Streptomycin, Gentamicin)

• Mechanism of Action: Aminoglycosides inhibit bacterial protein synthesis.
• Nursing Responsibilities:
  • Monitor renal function and signs of ototoxicity, particularly in patients receiving prolonged therapy.

iii. Macrolides (e.g., Erythromycin)

• Mechanism of Action: Macrolides also inhibit protein synthesis but are generally used for respiratory infections.
• Nursing Responsibilities:
  • Monitor for gastrointestinal side effects such as nausea and diarrhea.

iv. Tetracyclines

• Mechanism of Action: Inhibit protein synthesis by binding to the 30S ribosomal subunit.
• Nursing Responsibilities:
  • Educate patients about photosensitivity and the importance of avoiding sun exposure.

5. Medicines Acting on the Digestive System

Nurses need to be familiar with medications that manage gastrointestinal disorders, as these conditions are common among patients.

a. Antacids

• Examples: Aluminium hydroxide, magnesium trisilicate.
• Mechanism of Action: Neutralize stomach acid, providing symptomatic relief from heartburn and indigestion.
• Nursing Responsibilities:
  • Advise patients to take antacids at least one hour before or after other medications to avoid interference with absorption.

b. Antispasmodics (e.g., Hyoscine Butylbromide)

• Mechanism of Action: These agents relieve muscle spasms in the gastrointestinal tract.
• Nursing Responsibilities:
  • Monitor for side effects such as constipation and dry mouth.

c. Proton Pump Inhibitors (e.g., Omeprazole)

• Mechanism of Action: Reduce gastric acid secretion by blocking the proton pump in gastric parietal cells.
• Nursing Responsibilities:
  • Assess for potential interactions with other medications, as PPIs can affect absorption.

6. Current Drug Policies in Ghana

Understanding the current drug policies in Ghana is crucial for nurses, as these policies guide safe and effective medication use.

a. Essential Medicines List (EML)

The Essential Medicines List (EML) in Ghana outlines medications that are deemed necessary for addressing the most important health needs of the population. Nurses must familiarize themselves with this list to ensure they are prescribing and administering the most appropriate medications.

b. Drug Regulation and Quality Control

The Food and Drugs Authority (FDA) in Ghana is responsible for regulating the safety, efficacy, and quality of medicines. Nurses must be aware of FDA guidelines to ensure compliance in medication administration and patient safety.

7. Pharmacovigilance

Pharmacovigilance is the science and activities related to the detection, assessment, understanding, and prevention of adverse effects or any other drug-related problems. It is crucial for ensuring the safety of medicines in the population.

a. Key Terms in Pharmacovigilance

• Pharmacovigilance: The science of monitoring the safety of medicines and taking action to reduce risks and increase benefits.
• Vaccine Vigilance: A specific area of pharmacovigilance that focuses on monitoring the safety of vaccines.
• Patient Safety: Ensuring that patients do not experience adverse effects from medications and that any risks are minimized.

b. Importance of Pharmacovigilance

• Adverse Drug Reactions (ADRs): Pharmacovigilance helps in identifying and monitoring ADRs, ensuring that any issues are reported and managed promptly.
• Spontaneous Reporting Systems: Encourage healthcare professionals to report any suspected ADRs, which can provide valuable data for assessing drug safety.

c. The Pharmacovigilance System in Ghana

• The FDA oversees the pharmacovigilance system in Ghana. Nurses play a critical role in reporting any adverse drug reactions and ensuring that patients receive safe medications.

This Pharmacology, Therapeutics, and Pharmacovigilance I (RGN 217) Handout provides a comprehensive overview of essential pharmacological principles, nursing responsibilities in medication administration, and the importance of pharmacovigilance. Nurses are pivotal in ensuring patient safety and effective therapeutic outcomes through proper drug management and monitoring.

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