Core Pharmacology: Exhaustive Study Guide on Drug Development, Pharmacokinetics, and Clinical Practice

Learning Objectives for Core Pharmacology

• Differentiate between the generic and trade names of drugs.
• Describe the phases of drug development.
• Differentiate between drug schedules and between pregnancy categories.
• Outline the four phases of pharmacokinetics and describe the effects on an individual's response to medication.
• Identify two factors that influence how a drug affects the body.
• Describe adverse drug reactions and the nurse's responsibility in drug therapy.

Federal Drug Administration (FDA) Oversight and Regulation

• Drug Regulation: The FDA reviews and approves both prescription and over-the-counter (OTC) medications for safety and efficacy before they can be marketed to consumers.
• Blood and Biologics: The agency ensures the safety of blood products, vaccines, and other biological products used in medical treatments.
• Public Health Protection:     * Issues recalls, safety alerts, and guidance to protect consumers from harmful products.     * Provides science-based information to help people make informed health decisions.
• Other FDA Functions:     * Cosmetics and Dietary Supplements regulation.     * Food Safety oversight.     * Medical Device Oversight.     * Tobacco Control.     * Inspection and Enforcement of regulations.

The Drug Development Process and Timeline

• Basic Science: Initial research phase lasting approximately $1/2-2$ years.
• Research: Continued investigation spanning $2-5$ mm (as noted in transcript).
• Preclinical Testing: Laboratory and animal testing lasting $1-2$ years.
• Clinical Trials: Human testing phases lasting $5-7$ years.
• Government Approval: Final FDA review process lasting $1/2-2$ years.
• Approved Drug: The final stage where the medication becomes available for use.

1997 FDA Modernizing Act

• Fast Tracks: Provided for medications treating AIDS, cancer, and other life-threatening conditions.
• Discontinuation Notice: Manufacturers must provide 6 months' notice before discontinuing a drug.
• Pediatric Testing: The FDA can require testing of medications in children.
• Clinical Trial Database: Established a database for tracking clinical trials.
• Off-label Uses: Allowed drug companies to provide information regarding “off-label” uses of medications.

Classification and Nomenclature of Medications

• Drug Names:     * Chemical Name: The precise description of the drug's chemical structure (e.g., $N$-acetyl-para-aminophenol).     * Generic Name: The official name assigned to the drug (e.g., Acetaminophen).     * International Name: The name used globally (e.g., Paracetamol).     * Trade Name: The brand name given by the manufacturer (e.g., Tylenol).
• Drug Information and Labels:     * Drug Label: Found on the package containing essential information.     * Over-the-Counter (OTC): Medications available without a prescription.     * Associated Problems:         * Self-treatment issues.         * Example: Tums can alter the gastric environment, affecting the absorption of other medications.

Drug Enforcement Agency (DEA) Responsibilities

• Drug Law Enforcement: Investigates and prosecutes individuals and organizations involved in the illegal manufacture, distribution, and trafficking of controlled substances.
• Controlled Substances Regulation: Oversees legal production and dispensing of controlled substances to prevent diversion into illegal markets.
• International Drug Control: Coordinates with foreign governments to combat global trafficking networks.
• Scheduling and Classification: Assigns substances to schedules based on medical value and abuse potential.
• Prescription Monitoring: Regulates pharmacies, hospitals, and healthcare providers handling controlled substances.
• Other DEA Functions: Asset Forfeiture, Intelligence Gathering, Chemical Control, and Public Safety and Prevention.

DEA Schedules for Controlled Substances

• Schedule I: High abuse potential; no accepted medical use.
• Schedule II: High abuse potential; accepted medical use.
• Schedule III: Moderate abuse potential; accepted medical use.
• Schedule IV: Low abuse potential; accepted medical use.
• Schedule V: Low abuse potential; accepted medical use.

Nursing Responsibilities in Drug Therapy

• Administration Duties:     * Gathering Baseline Data.     * Adhering to the Five Rights of medication administration.     * Verifying Correct Dosing Range.     * Implementing Appropriate safety measures.
• Assessment: Continuous evaluation of the patient's condition.
• Intervention:     * Providing Education to the patient and family.     * Implementing non-drug measures to support therapy.     * Making informed PRN (as needed) medication decisions.
• Monitoring:     * Evaluating the therapeutic response.     * Promoting patient compliance.

Fundamentals of Pharmacokinetics and Pharmacodynamics

• Pharmacokinetics: The effect of the body on the drug. It consists of four phases:     * Absorption: The movement of the drug from its site of administration into the blood.     * Distribution: Movement of the medication from the bloodstream into the cells.     * Metabolism: The enzymatic alteration of drug structure.     * Excretion: The removal of drugs from the body.
• Pharmacodynamics: The effect of the drug on the body.
• Clinical Implications: Both pharmacokinetic and pharmacodynamic profiles influence drug dosing, drug effect, and the resulting physiologic response.

Pharmacokinetics: Absorption and Routes

• Routes of Administration:     * Enteral: Oral, Rectal, and specialized tubes (Nasogastric/NG, Gastrostomy, Dubhoff).     * Parenteral: Intramuscular (IM), Intravascular (IV), Subcutaneous (SQ).     * Topical: Applied to surfaces.     * Transdermal: Delivered via skin patches.     * Inhaled: Delivered through the respiratory system.
• Factors Affecting Absorption/Distribution:     * Rate of dissolution.     * Blood flow to the site.     * Lipid solubility of the drug.
• Long Acting Medications: Identified by specific suffixes and suffixes.     * Suffixes: LA, SR, EC, XL, -contin.     * Comparison: Oxycodone (short-acting) vs. Oxycontin (long-acting continuous release).

Pharmacokinetics: Distribution and Barriers

• Tissue Blood Flow:     * High flow areas: Lungs and Kidneys.     * Low flow areas: Bone and Feet.
• Exiting the Vascular System:     * Typical capillary beds allow easy exit.     * Blood Brain Barrier (BBB): Specialized barrier protecting the CNS.     * Placental and Breast Milk Transfer: Medications can cross into these compartments, affecting the fetus or infant.
• Protein Binding:     * Drugs often bind to albumin in the blood, which stays in the bloodstream and limits the amount of free drug available to enter cells.

Pharmacokinetics: Metabolism and the Hepatic System

• First Pass Effect: Oral medications are metabolized by the liver before reaching systemic circulation, which may significantly reduce the active drug amount.
• Hepatic Drug Metabolizing System:     * Cytochrome P450 System: A collection of enzymes involved in drug metabolism.     * Grapefruit Juice Interaction: Can inhibit enzymes, potentially leading to drug overdose (OD).
• Therapeutic Consequences of Metabolism:     * Accelerated renal drug excretion.     * Drug inactivation.     * Increased therapeutic action.     * Activation of prodrugs (inactive compounds converted to active forms).     * Change in toxicity (increase or decrease).

Cytochrome P450 (CYP) Enzyme Interactions

Pharmacokinetics: Excretion

• Renal Drug Excretion: Primary route via urine, heavily dependent on Renal Function.
• Alternative Routes of Excretion:     * Breast Milk.     * Bile.     * Sweat.     * Feces.
• Normal Serum Creatinine Values:     * Males: $0.6$ to $1.1\,mg/dL$.     * Females: $0.5$ to $1.1\,mg/dL$.     * Infants: $>0.2\,mg/dL$.     * Person With One Kidney: $1.8$ to $1.9\,mg/dL$.

Pharmacodynamics: Dose-Response and Receptors

• Dose-Response Relationships:     * Maximal Efficacy: The largest effect a drug can produce regardless of dose (e.g., Meperidine/Demerol has higher efficacy for pain relief than Pentazocine/Talwin).     * Potency: The amount of drug needed to produce a specific effect (e.g., Morphine is more potent than Meperidine because it requires a lower dose for the same pain relief).
• Key Kinetic/Dynamic Concepts:     * Critical Concentration: The amount of drug needed to achieve a therapeutic effect.     * Loading Dose: A higher initial dose than usual needed to reach therapeutic levels quickly.     * Dynamic Equilibrium: The concentration the drug reaches in the body over time.     * Half-Life: The time it takes for the drug concentration in the body to decrease to half of its PEAK level.

Drug-Receptor Interactions and Modes of Action

• Modes of Action:     * Agonists: Drugs that activate receptors.     * Antagonists: Drugs that inhibit or block receptors.     * Partial Agonists: Activate receptors slightly but also block them from being further activated (e.g., certain pain medications).
• Regulation of Sensitivity:     * Downregulation: Decrease in receptor number or sensitivity (e.g., Diabetes where insulin floods cell receptors).     * Upregulation: Increase in receptor number or sensitivity.
• Receptor Types:     * Cell Membrane-Embedded Enzymes.     * Ligand-Gated Ion Channels.     * G Protein-Coupled Receptor Systems.     * Transcription factors.
• Insulin Mechanism Example:     * Insulin acts as a key to unlock the glucose channel.     * Insulin binds to the receptor, causing the glucose channel to open.     * Glucose enters the cells once the channel is open.

Measures of Drug Safety: Therapeutic Index (TI)

• Therapeutic Index Formula: $TI = \frac{LD_{50}}{ED_{50}}$.     * $LD_{50}$: Lethal Dose in $50\%$ of subjects.     * $ED_{50}$: Effective Dose in $50\%$ of subjects.
• Drug Comparison:     * Drug "X": $TI = \frac{100}{1} = 100$ (Wider safety margin).     * Drug "Y": $TI = \frac{20}{10} = 2$ (Narrower safety margin; more dangerous).

Drug-Drug and Drug-Food Interactions

• Outcomes:     * Intensification: One drug increases the effect of another.     * Reduction: One drug decreases the effect of another.
• Interaction Mechanisms:     * Absorption changes.     * Metabolism changes (e.g., Grapefruit inhibiting metabolism).     * Increased Toxicity.     * Altered Drug Action.

Adverse Drug Reactions (ADR) and Side Effects

• Definition: Undesired effects that may be unpleasant or dangerous.
• Reasons for ADRs:     * The drug has effects beyond the intended therapeutic one.     * The patient is overly sensitive to the drug.     * The drug's primary actions are undesired (extension of effect).     * Dosage is too high or too low.
• Types of ADRs:     * Primary Actions: Extension of the desired effect (e.g., overdose causing excessive therapeutic response).     * Secondary Actions: Undesired effects in addition to the pharmacologic effects.     * Hypersensitivity: An excessive or exaggerated response to a drug.

Drug Allergies and Immune Responses

• Drug Allergy: Requires antibodies to the drug; immune response occurs upon re-exposure.
• Anaphylaxis:     * Interaction of Antibody, Site, and Chemical release.     * Affects 3 sites: Skin, Respiratory, Cardiovascular/Sympathetic Nervous System (SNS).
• Cytotoxic Reaction:     * Antibody causes cell death due to attack.     * Damage to blood-forming cells.     * Assessment: Decreased H/H (Hemoglobin/Hematocrit), WBC, and Platelets; Elevated LFTs (Liver Function Tests) and BUN/Creatinine.
• Serum Sickness:     * Antibodies cause deposition into vessels, damaging tissues.     * Occurs 1+ weeks after exposure.     * Symptoms: HIGH fever, lymphatic involvement, joint pain, leaky tissue.
• Delayed Allergic Reactions:     * Antibody + WBC interaction.     * Occurs hours to days after exposure.     * Affects Skin and Joints.

Drug-Induced Tissue and Organ Damage

• Dermatological (Derm): Rashes, Hives, and Stomatitis (inflammation of the mouth).
• Superinfections: Infections occurring due to the destruction of normal flora.
• Blood Dyscrasia: Bone marrow suppression; requires monitoring counts.
• Sensory Damage:     * Ocular damage.     * Auditory damage: Characterized by dizziness, tinnitus, balance issues, and Loss of Hearing (LOH).
• Neurological (Neuro):     * CNS effects like confusion.     * Anticholinergic Effects: Dry mouth, urinary retention, blurred vision.     * Parkinson-like syndrome: Tremors.     * Neuroleptic Malignant Syndrome (NMS): A severe reaction to antipsychotic drugs.

Toxicity, Poisoning, and Organ-Specific Injury

• Liver Injury:     * Assess for: Fever, Nausea (N), Jaundice, elevated LFTs.     * Intervention: Discontinue (d/c) medication.
• Renal Injury:     * Assess for: Change in urine output, elevated BUN/Creatinine.     * Intervention: Decrease dose or discontinue drug.
• Teratogenicity: Drugs reaching a fetus and causing developmental defects.
• Overdose: Damages multiple body systems; can lead to fatal reactions. Treatment varies by substance.

Response to Adverse Events

• Before Medication: Conduct Physical Assessment and check Vital Signs.
• If Adverse Effect is Identified:     1. STOP the medication immediately.     2. Notify the provider.

Medication Errors

• Definition: Any preventable event that may cause or lead to inappropriate medication use or harm.
• Statistics and Causes:     * Performance Deficits ($30\%$): Simply performing the task incorrectly.     * Knowledge Deficit ($14\%$): Not knowing the drug or correct procedure.     * Miscalculation of doses ($13\%$): Mathematical errors.     * Communication Mistakes ($15\%$): Issues with handwriting, abbreviations, or decimals.     * Name Confusion: Similar sounding or looking drug names.
• The Nurse's Role (The 8 Rights):     1. Right patient.     2. Right drug.     3. Right storage.     4. Right route.     5. Right dose.     6. Right preparation.     7. Right time.     8. Right documentation.

Challenges to Drug Therapy

• Access: Patient ability to obtain medications.
• Alternative Therapy: Use of herbal or non-traditional medicine.
• Consumer Demand: Pressure for specific treatments.
• Early Discharge: Less time for inpatient monitoring and education.
• Patient Education: CRITICAL for safety and compliance.
• Media Influence: Impact on patient perception of drugs.
• Source of Information: Where patients get their data.
• Off-label use: Use of drugs for non-approved indications.
• Drug Abuse and the Opioid Crisis: Societal impacts on therapy.