Usage
Chlorbutol + Tropicamide is prescribed for ophthalmic examinations, specifically for mydriasis (dilation of the pupil) and cycloplegia (paralysis of the ciliary muscle). It belongs to the pharmacological classifications of anticholinergics (tropicamide) and sedative-hypnotics (chlorbutol).
Tropicamide acts by blocking the action of acetylcholine at muscarinic receptors in the eye, causing the pupil to dilate and the ciliary muscle to relax. Chlorbutol acts as a preservative.
Alternate Names
This combination doesn’t have a universally recognized international nonproprietary name (INN). It may be referred to as Chlorobutanol + Tropicamide. Brand names vary regionally; some examples include “Mydriacyl” (containing tropicamide, often used with chlorbutol as a preservative).
How It Works
Pharmacodynamics: Tropicamide exerts its effect by competitively antagonizing acetylcholine at muscarinic receptors located in the iris sphincter and ciliary muscle. This antagonism leads to pupil dilation (mydriasis) and paralysis of accommodation (cycloplegia). Chlorbutol has weak local anesthetic, antiseptic and sedative hypnotic actions but primarily serves as a preservative in this formulation.
Pharmacokinetics: Tropicamide is rapidly absorbed following topical ocular administration. Its mydriatic effect peaks around 20-40 minutes after instillation, with a duration of action typically lasting for several hours (up to 6 hours), though this is dose-dependent. The drug is metabolized in the liver and excreted primarily via the kidneys. Chlorbutol is poorly absorbed from the topical route.
Dosage
Standard Dosage
Adults: Instill 1-2 drops of 1% tropicamide solution into the conjunctival sac. For optimal mydriasis, the dose can be repeated after 5 minutes. If needed, an additional drop can be given after another 30 minutes for full cycloplegic effect.
Children: The dosage in children should be adjusted based on age and clinical needs under careful supervision by a healthcare professional.
- Infants and young children: 1 drop of 0.5% or 1% solution may suffice. Repeat dosing should be done cautiously if necessary.
- Older children: 1 drop of 1% solution can be used. Repeat dosing can be considered if needed.
Special Cases:
- Elderly Patients: Similar to adults, but start with a lower dose and monitor closely.
- Patients with Renal/Hepatic Impairment: No specific dosage adjustments for tropicamide are typically required, as topical absorption is minimal. However, caution is advised in patients with severe hepatic dysfunction. For chlorbutol, caution is advised in patients with renal/hepatic impairment due to potential systemic absorption.
- Patients with Comorbid Conditions: No specific adjustments for tropicamide or chlorbutol are typically needed. However, exercise caution in patients with narrow-angle glaucoma or other ocular conditions.
Side Effects
Common Side Effects:
- Transient stinging or burning sensation upon instillation.
- Blurred vision.
- Photophobia (light sensitivity).
- Increased intraocular pressure.
Rare but Serious Side Effects:
- Allergic reactions (e.g., itching, redness, swelling).
- Angle-closure glaucoma (especially in predisposed individuals).
- Systemic anticholinergic effects (e.g., dry mouth, tachycardia, confusion) - primarily in children or with excessive dosages
Contraindications
- Primary angle-closure glaucoma or a predisposition to angle closure.
- Hypersensitivity to tropicamide or chlorbutol.
Drug Interactions
- Other anticholinergic drugs: May enhance anticholinergic effects.
- Nitrates and nitrites: May increase intraocular pressure.
Pregnancy and Breastfeeding
- Pregnancy: Tropicamide is classified as Pregnancy Category C. Use only if the potential benefit justifies the potential risk to the fetus.
- Breastfeeding: It is unknown whether tropicamide is excreted in human milk. Exercise caution while breastfeeding.
Drug Profile Summary
- Mechanism of Action: Tropicamide: Muscarinic receptor antagonist; Chlorbutol: Preservative.
- Side Effects: Transient stinging, blurred vision, photophobia, increased intraocular pressure.
- Contraindications: Angle-closure glaucoma, hypersensitivity.
- Drug Interactions: Anticholinergics, Nitrates
- Pregnancy & Breastfeeding: Pregnancy Category C; caution in breastfeeding
- Dosage: Adults: 1-2 drops of 1% solution; Children: adjust based on age.
Popular Combinations
Often used alone. Other mydriatics (phenylephrine) may be combined to achieve greater mydriasis.
Precautions
- Monitor intraocular pressure, especially in at-risk patients.
- Advise patients about temporary blurred vision and photophobia.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Chlorbutol + Tropicamide?
A: Adults: 1-2 drops of 1% tropicamide, repeated as needed. Children: adjust based on age and clinical need.
Q2: How long does the effect of Tropicamide last?
A: The mydriatic effect typically lasts for several hours (up to 6), while cycloplegia can last longer.
Q3: Can Chlorbutol + Tropicamide be used in patients with glaucoma?
A: Contraindicated in angle-closure glaucoma. Use with extreme caution in open-angle glaucoma under close monitoring.
Q4: Are there any systemic side effects of Tropicamide eye drops?
A: Systemic anticholinergic effects are rare but possible, especially in children or with high doses.
Q5: Can Chlorbutol + Tropicamide be used during pregnancy?
A: Pregnancy Category C. Use only if the potential benefit justifies the potential risk.
Q6: What are the common side effects of Chlorbutol + Tropicamide?
A: Stinging, blurred vision, and photophobia are common transient side effects.
Q7: How does Chlorbutol + Tropicamide work?
A: Tropicamide blocks muscarinic receptors in the eye, causing dilation and cycloplegia. Chlorbutol acts as a preservative.
Q8: Are there any drug interactions with Tropicamide?
A: Concurrent use of other anticholinergics or nitrates/nitrites should be approached with caution.
Q9: What should patients be advised after receiving Chlorbutol + Tropicamide?
A: Inform patients about transient blurred vision, photophobia, and the need to avoid driving or operating machinery until these effects subside.
