Methods-of-Drug-Classification

Objectives

  • Understand the Basic Principles of Drug Classification

  • Define and differentiate Pharmacokinetics and Pharmacodynamics

  • Discuss the manner in which drugs are absorbed, distributed, metabolized, and eliminated in the body

  • Understand and Apply Basic Measurement Units

  • Identify various routes of medication administration

  • List and describe the three mechanisms of drug action in Pharmacodynamics

Methods of Drug Classification

  1. Chemical Group

    • Classification based on chemical structure of drugs.

    • Drugs in the same group share similar properties, metabolism, and side effects.

    • Examples: Benzodiazepines, Opioids, Iodinated Contrast Media, Sulfonamides, Fluoroquinolones, Corticosteroids.

  2. Mechanism/Site of Action

    • Describes how a drug causes biochemical changes and the body parts affected.

    • Mechanism of Examples:

      • Receptors

      • Enzymes

      • Transporters

      • Ion Channels

    • Sites of Action Examples:

      • CNS

      • Cardiovascular system

      • Respiratory system

      • Musculoskeletal system

  3. Primary Effect

    • The therapeutic effect intended from the drug.

    • Examples:

      • Paracetamol: Reduces pain and fever

      • Insulin: Lowers blood glucose level

      • Salbutamol: Relaxes bronchial muscles

      • Morphine: Relieves pain

      • Omeprazole: Reduces stomach acid production

      • Iodinated Contrast Media: Enhances imaging contrast.

General Pharmacologic Principles

Pharmacokinetics

  • Definition: What the body does to a drug including absorption, distribution, metabolism, and elimination (ADME).

Pharmacokinetics Processes:

  1. Absorption

    • Movement from administration site to systemic circulation.

    • The rate depends on the route of administration.

  2. Distribution

    • Movement from systemic circulation to target sights.

    • Influenced by the rate and extent of distribution.

  3. Metabolism

    • Alteration of the drug's chemical structure by the body; can create active metabolites.

  4. Elimination (Excretion)

    • Removal of the drug from the body, mostly through kidneys.

    • Routes of Excretion:

      • Renal (Urine)

      • Hepatic (Bile/Feces)

      • Lungs (Exhalation)

      • Minor routes include sweat, saliva, and breast milk.

Pharmacodynamics

  • Definition: What the drug does to the body; focuses on the mechanism of action.

  • Drug-Receptor Interactions:

    • Receptors act as binding sites for drugs.

    • Drug actions are either agonist (stimulates response) or antagonist (blocks response).

Drug-Response Relationship

  • Efficacy: Degree of desired effect from the drug.

  • Potency: Relative concentration needed to achieve efficacy.

Indications and Contraindications

  • Indications: Approved uses of the drug for specific conditions.

  • Contraindications: Conditions that make drug use unsafe.

    • Absolute Contraindications: Must not use due to severe harm risks.

    • Relative Contraindications: Caution needed but may use if necessary.

Dosage and Calculations

  • Dose: Amount taken at one time.

  • Dosage Regimen: Includes amount, frequency, duration.

  • Special Terms:

    • Maintenance Dose: Keeps therapeutic level.

    • Loading Dose: Rapidly achieves therapeutic level.

    • Toxic Dose: Causes toxic effects.

    • Minimum Effective Dose: Smallest dose for effect.

Pediatric Dosage Calculations

  • Various formulas to adjust adult doses for child patients based on age and weight (Young's, Dilling's, Fried's).

Routes of Administration

  1. Oral (mouth)

  2. Intravenous (directly into vein)

  3. Intramuscular (through muscles)

  4. Subcutaneous (under skin)

  5. Sublingual/Buccal (under tongue/between gums and cheeks)

  6. Rectal (localized/systemic)

  7. Topical (skin/mucous membrane)

  8. Inhalation (respiratory tissues)

Side Effects and Complications

  • Side Effects: Unintended effects from a drug, varying by metabolism and dosage.

  • Pharmacokinetics Impact on Side Effects:

    • Absorption rate, distribution into tissues, metabolism speed, and excretion capability can increase side effect risks.

Compatibility and Special Considerations

  • Compatibility: Ability of substances to coexist without altering effectiveness.

  • Considerations: Medical history, allergies, age, sex, and other medications can influence drug actions and safety.