Routes of Administration Summary

Routes of Administration Overview

  • Dosage Form Design:

    • Drugs are typically mixed with excipients (e.g., paracetamol 500 mg tablet).
    • Formulated medicines are delivered as dosage forms for better administration, convenience, and controlled therapeutic response.

  • Requirements for Dosage Forms:

    • Performance is reproducible and acceptable to patients.
    • Must allow for large-scale production and reproducible quality with minimal variation.
    • Physically and chemically stable with effective preservation.

  • Dosage Form Design Considerations:

    • New drug substances require understanding of therapeutic considerations and drug factors that impact performance (e.g., particle size).
    • Important biochemical parameter considerations (ADME).
    • Routes of Administration: oral, parenteral, topical, rectal, respiratory, nasal, eye, ear.

Types of Administration Routes

  • Oral Route:

    • Most common, involving swallowing immediate release tablets.
    • Advantages: convenient and safe.
    • Disadvantages: includes lag time, hostile environment (pH, enzymes), variable absorption, first pass metabolism effects, gastrointestinal irritation.

  • Solid Dosage Forms:

    • Tablets: Most common (70%); available in various forms (e.g., coated).
    • Capsules: Gelatin shells; used for liquids and to mask taste/smell.

  • Liquid Dosage Forms:

    • Solutions: Homogeneous mixtures; improved absorption.
    • Suspensions: Insoluble drugs in suitable vehicle.
    • Emulsions: Mixture of immiscible liquids.

  • Parenteral Route:

    • Involves injecting drugs - includes subcutaneous, intramuscular, intravenous routes.
    • Advantages: rapid onset and high bioavailability without first-pass metabolism; sterile conditions.

  • Topical Route:

    • Applied on skin for local/systemic effect; limited side effects but poor absorption.
    • Forms include creams, ointments, gels, and patches.

  • Rectal Route:

    • Used for local/systemic action; bypasses first-pass metabolism; unpredictable absorption.

  • Respiratory Route:

    • Local effects via gaseous/mist delivery; minimal side effects dependent on particle size.
    • Requires inhaler devices (e.g., pMDI, DPI, nebulizers).

Selecting the Route of Administration

  • Determined by:
    • Physical characteristics of the drug.
    • Absorption and release rate.
    • Need to bypass hepatic metabolism for site-specific high concentrations.
    • No single method suits all drugs in all contexts.