1. Clinical Overview
Carboxymethylcellulose (CMC) 5mg/ml is a sterile, topical ophthalmic solution classified as an ocular lubricant and demulcent. It is a purified, high molecular weight polymer derived from cellulose, functioning as a viscosity-enhancing agent and artificial tear. In the Indian context, it is a first-line, over-the-counter (OTC) treatment for dry eye disease (DED), a highly prevalent condition exacerbated by pollution, digital screen use, and climatic conditions. It acts by mimicking the mucin layer of the tear film, stabilizing it, and providing prolonged lubrication and protection to the ocular surface.
| Onset | Duration | Bioavailability |
|---|---|---|
| Immediate upon instillation. | Approximately 60 to 90 minutes per instillation, depending on the severity of tear film instability. | Topical ophthalmic; systemic absorption is negligible (<1%). |
2. Mechanism of Action
Carboxymethylcellulose is a polyanionic, water-soluble polymer that acts as a lubricant, wetting agent, and mucin substitute. Its primary mechanism is to adsorb to the hydrophobic corneal and conjunctival epithelium, forming a hydrophilic layer that stabilizes and thickens the precorneal tear film. This increases the tear film breakup time (TBUT), protects surface epithelial cells from desiccation, and promotes healing of minor epithelial irregularities.
3. Indications & Uses
- Dry Eye Disease (DED) / Keratoconjunctivitis Sicca
- Tear Film Insufficiency
- Exposure Keratitis
- Post-operative ocular surface lubrication (post-cataract, post-LASIK, post-PRK)
4. Dosage & Administration
Adult Dosage: One to two drops in the affected eye(s) as needed, typically 3 to 4 times daily or more frequently based on symptom severity.
Administration: 1. Wash hands. 2. Tilt head back. 3. Gently pull lower eyelid down to form a pouch. 4. Instill drop(s) into the pouch without touching the dropper tip to eye, eyelid, or any surface. 5. Close eyes gently for 1-2 minutes. Apply gentle pressure to the nasolacrimal duct (inner corner of eye) for 30 seconds to minimize systemic drainage if needed. 6. Wait at least 5-10 minutes before instilling any other topical ophthalmic medication. For single-dose units: discard vial immediately after use.
5. Side Effects
Common side effects may include:
- Transient mild blurring of vision immediately after instillation
- Mild ocular discomfort or stinging upon application (usually resolves quickly)
- Sticky eyelashes upon drying
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Topical Ophthalmic Medications (e.g., antibiotics, glaucoma drops) | Physical incompatibility or dilution/washout effect if instilled simultaneously. | Moderate |
| Topical Ophthalmic Ointments | CMC solution may not adhere properly to ocular surface if an ointment base is present. Separate administration by at least 10 minutes. | Low |
7. Patient Counselling
- DO wash hands before use.
- DO keep the dropper tip clean and avoid contamination.
- DO wait 5-10 minutes between different eye drops.
- DO NOT touch the tip of the dropper to your eye or any surface.
- DO NOT use if the solution is discolored or contains particles.
- DO NOT share your eye drops with others.
- DO remove contact lenses before application unless the product is labeled as 'for use with contacts'. Wait 15 minutes before reinserting lenses.
8. Toxicology & Storage
Overdose: Virtually non-toxic topically. Accidental ingestion of eye drops may cause gastrointestinal discomfort (nausea, diarrhea) due to the osmotic effect of the solution.
Storage: Store at room temperature (15°C to 25°C). Protect from light. Do not freeze. Keep the bottle tightly closed when not in use. For single-dose units: store in pouch, use immediately after opening, and discard any unused solution.