Nasal preparations are pharmaceutical dosage forms designed for administration through the nasal route. They are formulated to deliver drugs either locally to the nasal cavity or systemically via absorption through the nasal mucosa.
Types of Nasal Preparations
1. Nasal Drops:Liquid formulations instilled into the nasal cavity using a dropper.
Use: Localized relief for conditions like rhinitis, nasal congestion.
Example: Sodium chloride 0.9% for nasal congestion.
2. Nasal Sprays: Dispensed as a fine mist using a spray device.
Use: Deliver drugs evenly to the nasal mucosa for local or systemic effects.
Example: Oxymetazoline hydrochloride (decongestant).
3. Nasal Inhalers: Cylindrical devices containing volatile drugs, inhaled through the nostrils.
Use: Relieve nasal congestion.
Example: Menthol and eucalyptus oil.
4. Nasal Gels: Semi-solid formulations that provide prolonged contact with the nasal mucosa.
Use: Moisturize dry nasal passages or deliver drugs.
Example: Mupirocin nasal gel (antibacterial).
5. Nasal Powders: Dry formulations delivered via specialized devices.
Use: Systemic delivery of peptides or vaccines.
Example: Sumatriptan powder for migraines.
6. Nasal Solutions (Irrigation): Isotonic or hypertonic saline solutions used for cleansing the nasal cavity.
Use: Treat sinusitis or remove debris/allergens.
Example: Sterile saline solution.
Mechanism of Drug Delivery via Nasal Route
The nasal cavity offers unique advantages due to its vascularized mucosa and large surface area. Drugs can be absorbed directly into the systemic circulation, bypassing the first-pass metabolism in the liver. The mechanism of drug absorption involves:
1. Transcellular Route: Drug molecules pass through epithelial cells.
2. Paracellular Route: Drug molecules pass between epithelial cells.
Applications of Nasal Preparations
1. Local Applications
Decongestants: Relieve nasal congestion (e.g., oxymetazoline).
Antihistamines: Treat allergic rhinitis (e.g., azelastine).
Antimicrobials: Treat bacterial infections (e.g., mupirocin).
2. Systemic Applications
Hormones: Calcitonin for osteoporosis.
Vaccines: Influenza vaccines.
Migraine Treatments: Sumatriptan nasal spray.
3. Diagnostic and Therapeutic Agents
Radiolabeled compounds for imaging studies.
Gene delivery for potential treatment of diseases.
Advantages of Nasal Preparations
1. Rapid Onset of Action: Quick absorption through the nasal mucosa.
2. Non-Invasive: A painless alternative to injections.
3. Bypasses First-Pass Metabolism: Enhances bioavailability for certain drugs.
4. Localized Treatment: Minimizes systemic side effects.
5. Convenience: Suitable for self-administration.
Limitations of Nasal Preparations
1. Limited Drug Absorption: Due to mucosal barriers or enzyme activity.
2. Irritation: Prolonged use may irritate the nasal mucosa.
3. Short Retention Time: Nasal secretions and mucociliary clearance can reduce drug contact time.
4. Restricted Volume: Only small volumes (~25–200 µL) can be administered.
5. Taste or Smell Disturbances: Some drugs may affect taste or smell.
Formulation Considerations
1. pH: Should match the nasal mucosa (pH 4.5–6.5) to prevent irritation.
2. Isotonicity: Formulations should be isotonic with nasal secretions.
3. Viscosity: Controlled using polymers like hydroxypropyl methylcellulose to enhance retention.
4. Preservatives: Prevent microbial contamination (e.g., benzalkonium chloride).
5. Absorption Enhancers: Substances like surfactants or bile salts to improve permeability.
Examples of Common Nasal Preparations
| Drug | Formulation Type | Use | Example Brand |
| Oxymetazoline | Spray/Drops | Nasal decongestion | Afrin, Nasivion |
| Sumatriptan | Nasal Spray | Migraine relief | Onzetra, Tosymra |
| Budesonide | Nasal Spray | Allergic rhinitis | Rhinocort |
| Mupirocin | Gel | Bacterial infection | Bactroban Nasal |
| Influenza vaccine | Nasal Spray | Flu prevention | FluMist |
Storage and Stability
Nasal preparations should be stored in cool, dry conditions, often below 25°C.
Avoid contamination by ensuring proper sealing and using preservatives.
Conclusion
Nasal preparations are versatile and effective dosage forms suitable for both local and systemic drug delivery. With ongoing advancements in formulation technology, the nasal route continues to be explored for novel therapies, including vaccines, peptide delivery, and gene therapy.
