1. Clinical Overview
Atropine (1% w/v) is a sterile ophthalmic solution containing the antimuscarinic alkaloid atropine sulfate, equivalent to 1% w/v atropine. It is a non-selective, competitive antagonist of acetylcholine at muscarinic receptors (M1-M5). In ophthalmology, it acts as a potent cycloplegic (paralyzing the ciliary muscle) and mydriatic (dilating the pupil), with a very long duration of action. Its primary clinical use in India is for cycloplegic refraction in children, treatment of uveitis, and as a penalization therapy in amblyopia management. It is also used pre-operatively in ophthalmic surgery and in the management of acute iridocyclitis.
| Onset | Duration | Bioavailability |
|---|---|---|
| Mydriasis: 30-40 minutes. Cycloplegia: 60-180 minutes. | Mydriasis: 7-10 days. Cycloplegia: Up to 12-14 days. | Systemic absorption via nasolacrimal duct is minimal but significant. Ocular bioavailability is high due to direct application. |
2. Mechanism of Action
Atropine competitively blocks the action of acetylcholine at postganglionic muscarinic receptors in the sphincter pupillae and ciliary muscles of the eye. Blockade of the parasympathetic tone allows unopposed sympathetic action, leading to relaxation of the sphincter pupillae (causing mydriasis) and relaxation of the ciliary muscle (causing cycloplegia or paralysis of accommodation).
3. Indications & Uses
- Cycloplegic refraction, especially in children and young adults.
- Treatment of anterior uveitis (iritis, iridocyclitis) to prevent synechiae formation and relieve pain/spasm.
- Pre-operative mydriasis for ophthalmic surgeries (e.g., cataract).
4. Dosage & Administration
Adult Dosage: For uveitis: Instill 1-2 drops into the affected eye(s) up to 3-4 times daily. For pre-operative mydriasis: 1-2 drops, 1 hour before surgery. Frequency and duration are highly indication-specific and must be individualized.
Administration: 1. Wash hands. 2. Tilt head back. 3. Gently pull lower eyelid to form a pouch. 4. Instill prescribed number of drops. 5. Close eyes gently and apply pressure to the lacrimal sac (inner corner of eye) for 1-2 minutes to minimize systemic absorption. 6. Do not blink excessively. 7. Do not touch dropper tip to any surface. 8. Wait at least 5-10 minutes before instilling any other eye drop.
5. Side Effects
Common side effects may include:
- Transient stinging/burning on instillation.
- Blurred vision (due to cycloplegia).
- Photophobia.
- Pupillary dilation (mydriasis).
- Dryness of the mouth (xerostomia).
- Increased heart rate (tachycardia).
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other anticholinergic drugs (e.g., Ipratropium, Oxybutynin, Tricyclic Antidepressants, Phenothiazines) | Additive systemic anticholinergic side effects (dry mouth, constipation, urinary retention, tachycardia, confusion). | Major |
| Potassium Chloride (wax-matrix tablets) | Increased risk of GI lesions due to reduced GI motility. | Moderate |
| Digoxin | Increased serum digoxin levels due to reduced GI motility, potentially leading to toxicity. | Moderate |
| Ketoconazole, Macrolide antibiotics | Potential to inhibit atropine metabolism, increasing systemic levels. | Moderate |
| Pilocarpine, Carbachol (miotics) | Pharmacological antagonism; atropine will counteract the effects of these drugs. | Major |
7. Patient Counselling
- DO apply pressure on the inner corner of the eye (lacrimal sac) for 1-2 minutes after instillation.
- DO wash hands before and after use.
- DO keep the bottle tip clean and avoid touching it.
- DO wait at least 5-10 minutes before using another eye medication.
- DO NOT drive, operate machinery, or perform hazardous tasks while vision is blurred.
- DO NOT wear contact lenses during treatment unless advised by doctor.
- DO NOT use in the other eye or for any other condition unless prescribed.
8. Toxicology & Storage
Overdose: SYSTEMIC: Dry mouth, difficulty swallowing, thirst; blurred vision, photophobia; tachycardia, palpitations; hot, dry, flushed skin; fever; restlessness, confusion, hallucinations, delirium, seizures, coma; urinary retention, reduced bowel sounds. OCULAR: Extreme mydriasis and cycloplegia lasting weeks, increased intraocular pressure.
Storage: Store at controlled room temperature (15°C to 25°C). Protect from light. Keep the bottle tightly closed. Do not freeze. Keep out of reach and sight of children. Discard the solution one month after opening the bottle (check manufacturer's instructions). Do not use if the solution is discolored or contains particles.