The traditional routes of drug administration, such as oral (through swallowing) or parenteral (injections), have several limitations like poor bioavailability, enzymatic degradation, or the need for frequent dosing.
To overcome these challenges, researchers are continually looking for alternative routes to deliver drugs efficiently and with minimal side effects.
One such promising route is the mucosal drug delivery system.
Definition:
Mucosal drug delivery pertains to the administration of drugs directly through the mucous membranes.
The major mucosal routes include the oral (buccal or sublingual), nasal, pulmonary (lungs), vaginal, and rectal mucosa.
The mucous membranes are thin sheets of tissue cells that line various cavities in the body, secreting mucus, which is a viscous fluid.
Advantages:
I. Rapid Absorption:
The mucous membranes have a rich blood supply, allowing for rapid absorption of drugs directly into the systemic circulation.
II. Bypassing First-pass Metabolism:
Drugs delivered through mucosal routes, especially sublingually or buccally, can bypass the liver's first-pass metabolism, thus improving the bioavailability of many drugs.
III. Avoidance of Enzymatic Degradation:
The stomach's acidic environment and digestive enzymes often degrade orally ingested drugs. Mucosal delivery can bypass this degradation.
IV. Convenience:
Mucosal routes can be more patient-friendly, eliminating the need for injections or swallowing large pills.
Classification:
Mucosal drug delivery, as a subset of NDDS, focuses on administering drugs through mucous membranes.
Based on the site of administration and intended effect, mucosal drug delivery can be broadly classified into the following categories:
I. Oral Mucosal Delivery:
A. Buccal Delivery:
Drugs are placed in the cheek region for absorption through the buccal mucosa. It's suitable for sustained drug release and bypassing first-pass metabolism.
B. Sublingual Delivery:
Drugs are placed under the tongue and are absorbed through the sublingual mucosa. This ensures rapid onset of action and also avoids first-pass metabolism.
II. Nasal Delivery:
Utilizes the nasal mucosa for drug administration.
Can be used for both local (e.g., nasal decongestants) and systemic effects (e.g., treatments for migraines or osteoporosis).
III. Pulmonary Delivery:
Targets the lungs' mucosa using inhalers or nebulizers.
Ideal for local treatment of respiratory diseases (e.g., asthma, COPD) but can also be employed for systemic drug delivery.
IV. Rectal Delivery:
Drugs are introduced into the rectum, primarily for local effects (e.g., treating inflammation) but can also have systemic effects.
Useful when oral administration is compromised due to vomiting or other reasons.
V. Vaginal Delivery:
Involves the vaginal mucosa.
Often used for local treatments (e.g., antifungal creams) but can also deliver systemic drugs (e.g., hormone therapies).
VI. Ophthalmic Delivery:
Targets the mucous membrane of the eyes.
Mostly used for local treatments, such as treating eye infections or providing lubrication.
VII. Otic Delivery:
For delivering drugs to the ear canal for local effect, primarily used for conditions like ear infections.
VIII. Intestinal Delivery:
Though not commonly classified under mucosal delivery, there are NDDS techniques that target the intestinal mucosa for more efficient drug absorption.