Usage
Cyclopentolate is prescribed for inducing mydriasis (pupil dilation) and cycloplegia (paralysis of accommodation) for ophthalmic examinations and procedures. It is also used in the treatment of certain inflammatory eye conditions like iritis and uveitis. Its pharmacological classification is anticholinergic, specifically an antimuscarinic agent. It blocks the action of acetylcholine at muscarinic receptors in the eye, inhibiting the constriction of the pupil and ciliary muscle contraction.
Alternate Names
It is also known as Cyclopentolate Hydrochloride. Brand names include Cyclogyl, AK-Pentolate, Cylate, Ocu-Pentolate, and others. Minims Cyclopentolate is a single-use unit dose formulation available.
How It Works
Pharmacodynamics: Cyclopentolate competitively blocks the action of acetylcholine at muscarinic receptors in the eye, primarily the M3 subtype, which results in relaxation of the iris sphincter muscle (mydriasis) and ciliary muscle (cycloplegia).
Pharmacokinetics: Cyclopentolate is administered topically as eye drops. The onset of mydriasis and cycloplegia is rapid, typically within 25–75 minutes, peaking around 30-60 minutes. The duration of action is relatively short, generally 6–24 hours for accommodation recovery and up to several days for complete mydriasis reversal, though it can vary. Systemic absorption can occur, especially in infants and young children, potentially leading to central nervous system (CNS) side effects. It is primarily eliminated through the kidneys following systemic absorption.
Mode of Action: Cyclopentolate binds to muscarinic receptors without activating them. This binding prevents acetylcholine from binding and triggering the normal physiological responses of pupillary constriction and accommodation. It does not have significant effects on other receptors or enzymes within the eye.
Dosage
Standard Dosage
Adults:
One to two drops of 0.5%, 1%, or 2% solution instilled into the conjunctival sac. This can be repeated after 5–10 minutes if needed. For pigmented irides, a 2% solution or repeated doses might be necessary.
Children:
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3 months – 12 years: One drop of 1% solution. A second drop of 0.5% or 1% solution may be administered after 5-10 minutes if needed. Close monitoring for 45 minutes after administration is recommended.
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>12 years: One drop of 0.5% solution, repeated after 10 minutes if required. Alternatively, the adult dosing of one to two drops of 1% or 2% solution can be utilized.
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< 3 months: Not recommended; if absolutely necessary, a single drop of 0.5% is considered. Close monitoring is essential.
Special Cases:
- Elderly Patients: Start with a lower concentration (0.5% or 1%) due to potential increased sensitivity and risk of elevated intraocular pressure (IOP). Monitor IOP closely.
- Patients with Renal Impairment: Caution is advised, although dose adjustment is not typically required for topical ophthalmic use. Monitor for systemic side effects.
- Patients with Hepatic Dysfunction: No specific dose modifications necessary, as the drug does not undergo significant hepatic metabolism. However, monitor for systemic effects.
- Patients with Comorbid Conditions: Exercise caution in patients with Down syndrome, brain damage, spastic paralysis, tachycardias, or other conditions that could make them more susceptible to anticholinergic side effects.
Clinical Use Cases
Dosing for specific medical settings mirrors standard dosing guidelines. Ensure pressure is applied to the nasolacrimal sac for 2-3 minutes after instillation to minimize systemic absorption.
Side Effects
Common Side Effects:
Blurred vision, burning or stinging sensation upon instillation, increased sensitivity to light (photophobia), dry mouth.
Rare but Serious Side Effects:
Psychotic reactions, behavioral disturbances, hallucinations (particularly in children), CNS disturbances (including drowsiness, ataxia, restlessness, seizures), tachycardia, increased intraocular pressure.
Adverse Drug Reactions (ADR):
Severe allergic reactions (rare), including skin rash, itching, swelling, difficulty breathing. Angle-closure glaucoma in predisposed individuals.
Contraindications
- Untreated narrow-angle or anatomically narrow angles glaucoma
- Hypersensitivity to cyclopentolate or any component of the formulation
Drug Interactions
Cyclopentolate may interfere with the ocular hypotensive effects of cholinergic agents like carbachol and pilocarpine. It can potentiate the anticholinergic effects of other systemic anticholinergic drugs (e.g., antihistamines, tricyclic antidepressants).
Pregnancy and Breastfeeding
Pregnancy Safety Category: C. Use only if the potential benefit outweighs the risk to the fetus. It’s unknown whether cyclopentolate is excreted in breast milk. Exercise caution when administering to nursing women. Consider withholding breastfeeding for four hours following administration.
Drug Profile Summary
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Mechanism of Action: Competitive antagonist at muscarinic receptors in the eye (mainly M3).
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Side Effects: Blurred vision, burning/stinging, photophobia, dry mouth, (rarely) CNS disturbances, psychotic reactions, increased IOP, allergic reactions.
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Contraindications: Narrow-angle glaucoma, hypersensitivity to cyclopentolate.
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Drug Interactions: Cholinergic miotics (e.g., pilocarpine, carbachol), systemic anticholinergics.
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Pregnancy & Breastfeeding: Category C; caution advised.
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Dosage: Adult: 1-2 drops 0.5-2%; Pediatric 3 months-12 years: 1 drop 1%; > 12 years: adult dose or 1 drop 0.5%; Adjust for specific use cases.
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Monitoring Parameters: Intraocular pressure, especially in elderly or at-risk patients, as well as observing for CNS side effects, particularly in children.
Popular Combinations
Cyclopentolate is often used alone for diagnostic purposes. In therapeutic settings, it may be combined with other ophthalmic medications like corticosteroids for treating inflammatory eye conditions.
Precautions
- Apply pressure to the nasolacrimal sac after instillation to minimize systemic absorption.
- Avoid touching the dropper tip to any surface.
- Advise patients not to drive or operate machinery until blurred vision resolves.
- Monitor infants and young children closely for CNS effects.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Cyclopentolate?
A: Adults: 1-2 drops of 0.5-2% solution. Children 3 months-12 years: one drop of 1% solution. Over 12 years: adult dose or one drop of 0.5%.
Q2: How long does it take for Cyclopentolate to take effect?
A: Mydriasis and cycloplegia typically occur within 25-75 minutes, with peak effects around 30-60 minutes.
Q3: What are the common side effects of Cyclopentolate?
A: Blurred vision, burning or stinging, photophobia, dry mouth.
Q4: What are the contraindications for Cyclopentolate use?
A: Narrow-angle glaucoma and hypersensitivity to the drug or its components.
Q5: How long do the effects of Cyclopentolate last?
A: Effects generally last 6-24 hours for accommodation and up to several days for pupil dilation, though it can vary.
Q6: Are there any specific precautions for pediatric patients?
A: Infants and young children are particularly susceptible to systemic anticholinergic effects. Use lower concentrations (0.5%) and monitor closely for CNS side effects. Consider withholding feeding for 4 hours after administration in infants.
Q7: What should be done in case of an overdose?
A: For topical overdose, flush eyes with water. For ingestion, supportive care and symptomatic treatment may be needed. Physostigmine may be considered as an antidote for severe systemic anticholinergic effects.
Q8: Can Cyclopentolate be used during pregnancy?
A: It’s a Pregnancy Category C drug, meaning it should be used only if the potential benefit justifies the potential risk to the fetus.
Q9: Does Cyclopentolate interact with other medications?
A: It can interact with cholinergic miotics (e.g., pilocarpine) and potentiate the effects of systemic anticholinergics.
