Definition
The ability of substances to pass across mucous membranes (e.g., oral, nasal, intestinal), which act as barriers yet allow drug passage for systemic or local effects.
Anatomy of Buccal Mucosa:
Epidermal Layer: Non-keratinized stratified squamous epithelium allowing for better drug permeability.
Rich Blood Supply: Facilitates quick systemic absorption of the drug.
Minimal Enzymatic Activity: Reduces the likelihood of drug degradation.
Classification of Transmucosal Drug Delivery
Oral: Sublingual (under tongue) or buccal (cheek pouch).
Nasal: Drug delivered via nasal mucosa.
Pulmonary: Drug delivered to lungs via inhalation.
Rectal: Drug administered into rectum.
Vaginal: Drug administered into the vaginal cavity.
Ocular: Drug applied to the eye.
Otic: Drug delivered to the ear.
Factors Influencing Transmucosal Permeability
Substance Nature: Lipophilic and small molecules permeate more easily.
Mucosal Thickness: Thicker membranes reduce permeability.
Surface Area: Larger areas (e.g., intestines) allow more absorption.
Blood Flow: Higher flow can aid faster absorption.
Tight Junctions: Regulate passage across cells.
pH and Charge: pH affects drug ionization, impacting permeability.
Enzymatic Barriers: Enzymes may break down drugs, reducing absorption.
Advantages of Enhanced Transmucosal Permeability
Rapid Action: Quick systemic entry.
Avoids First-Pass Metabolism: Prevents liver degradation.
Alternative to Injection: Less invasive delivery.
Strategies to Improve Permeability
Penetration Enhancers: Temporarily loosen tight junctions.
Nanocarriers: Liposomes and nanoparticles improve absorption.
Prodrug Approach: Modifies drugs to enhance permeability, converting back to active forms inside the body.