Usage
Chlorbutol + Proparacaine ophthalmic solution is prescribed for short-term local anesthesia of the cornea and conjunctiva. It’s utilized for diagnostic and minor surgical procedures, including:
- Tonometry
- Gonioscopy
- Removal of corneal foreign bodies
- Removal of corneal sutures
Pharmacological Classification: Local anesthetic (topical ophthalmic)
Mechanism of Action: Proparacaine, an ester-type local anesthetic, reversibly blocks nerve conduction by inhibiting sodium influx through voltage-gated sodium channels in nerve axons. This action prevents the initiation and propagation of pain signals. Chlorbutol serves as an antimicrobial preservative.
Alternate Names
- Paracain
- Alcaine
- Ophthetic (for proparacaine)
- Proxymetacaine (for proparacaine)
- Chlorbutanol (for chlorbutol)
Brand Names:
- Cainpro
- Iricain
- Oproxy
- P Caine
How It Works
Pharmacodynamics: Proparacaine blocks nerve conduction by preventing sodium ion influx into nerve cells, thereby preventing the initiation and propagation of action potentials along the nerve fibers. This localized action results in temporary numbing of the cornea and conjunctiva.
Pharmacokinetics:
- Absorption: Proparacaine is rapidly absorbed into the cornea and conjunctiva.
- Metabolism: Primarily hydrolyzed by plasma cholinesterases.
- Elimination: Metabolites are excreted in the urine. Chlorbutol exhibits low systemic absorption when used topically in the eye.
Mode of Action: Proparacaine binds to voltage-gated sodium channels in nerve cell membranes, blocking sodium ion influx. This inhibition prevents depolarization and the generation of action potentials, effectively blocking nerve conduction and producing local anesthesia.
Elimination Pathways: Proparacaine is metabolized by plasma cholinesterases, and the metabolites are excreted in the urine. Chlorbutol, when absorbed systemically, is metabolized primarily in the liver.
Dosage
Standard Dosage
Adults:
- Tonometry/Suture Removal: 1-2 drops instilled in the affected eye(s) 2-3 minutes before the procedure.
- Minor Corneal/Conjunctival Procedures: 1 drop instilled every 5-10 minutes for 5-7 doses.
Children:
Similar to adult dosing, but administer with careful observation due to the potential for systemic absorption, especially in infants. Use only if clearly necessary and ensure accurate dosing to avoid excessive application.
Special Cases:
- Elderly Patients: No specific dosage adjustments are generally required, but monitor for potential systemic toxicity due to age-related physiological changes.
- Patients with Renal Impairment: No specific dosage adjustments are recommended as proparacaine is primarily metabolized by plasma cholinesterases. Exercise caution and consider the potential for chlorbutol accumulation.
- Patients with Hepatic Dysfunction: Use with caution due to limited data regarding the effect of hepatic impairment on proparacaine metabolism. Consider the potential for chlorbutol accumulation.
- Patients with Comorbid Conditions: Caution is recommended in patients with cardiovascular disease or hyperthyroidism, as systemic absorption might induce adverse effects. Individualized dosing and close monitoring are essential.
Clinical Use Cases
Dosage for Intubation, Surgical Procedures, Mechanical Ventilation, ICU Use, and Emergency Situations is generally the same as the standard adult dosage. The drug is usually administered in a clinical setting under direct medical supervision, and prolonged use should be avoided.
Dosage Adjustments
Adjustments should be made based on patient-specific factors, including age, weight, renal function, and concurrent medications. Close monitoring is crucial, especially in special populations.
Side Effects
Common Side Effects:
- Transient stinging, burning, or discomfort upon instillation
- Conjunctival redness
- Lacrimation (tearing)
- Blurred vision
Rare but Serious Side Effects:
- Severe allergic reactions (e.g., contact dermatitis, keratitis, iritis)
- Corneal opacification (with prolonged use)
Long-Term Effects:
Corneal damage and visual impairment can occur with prolonged or excessive use.
Adverse Drug Reactions (ADR):
Severe allergic reactions (e.g., anaphylaxis, angioedema) require immediate medical intervention.
Contraindications
- Known hypersensitivity to proparacaine, chlorbutol, or any component of the formulation
Drug Interactions
No significant drug interactions are documented for topical ophthalmic proparacaine. However, be aware of potential interactions with other drugs metabolized by cholinesterases and those that prolong the QT interval. Space concomitant use with other topical ophthalmic medications appropriately.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C (Use only if the potential benefit outweighs the potential fetal risk.)
- Fetal Risks: The drug may cross the placental barrier.
- Breastfeeding: It is unknown whether proparacaine is excreted in breast milk. Exercise caution during lactation.
Drug Profile Summary
- Mechanism of Action: Blocks voltage-gated sodium channels, preventing nerve conduction.
- Side Effects: Stinging, burning, redness, tearing, blurred vision, allergic reactions (rarely severe).
- Contraindications: Hypersensitivity to proparacaine, chlorbutol, or any components.
- Drug Interactions: Potential interactions with cholinesterase inhibitors and drugs prolonging the QT interval.
- Pregnancy & Breastfeeding: Use with caution; potential fetal risk; unknown if excreted in breast milk.
- Dosage: 1-2 drops for tonometry/suture removal; 1 drop every 5-10 min for 5-7 doses in minor procedures.
- Monitoring Parameters: Observe for allergic reactions, corneal changes, and systemic toxicity.
Popular Combinations
No specific popular combinations for Chlorbutol + Proparacaine are widely established. It’s typically used alone as a topical anesthetic.
Precautions
- General Precautions: Screen for allergies, metabolic disorders, and organ dysfunction.
- Pregnant Women: Assess risk/benefit ratio carefully before use.
- Breastfeeding Mothers: Advise caution due to potential neonatal exposure.
- Children & Elderly: Monitor closely for systemic effects due to potential increased absorption.
- Lifestyle Considerations: Advise patients to avoid rubbing or touching their eye while anesthetized and inform them that temporary blurred vision may affect driving or operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Chlorbutol + Proparacaine?
A: For adults and children: 1-2 drops for tonometry/suture removal; 1 drop every 5-10 minutes for 5-7 doses for minor corneal/conjunctival procedures.
Q2: What are the common side effects?
A: Common side effects include transient stinging, burning, redness, tearing, and blurred vision.
Q3: Is it safe to use during pregnancy?
A: Pregnancy Safety Category C: Use only if the potential benefit justifies the potential risk to the fetus.
Q4: How does proparacaine work?
A: It blocks voltage-gated sodium channels, inhibiting nerve conduction and producing local anesthesia.
Q5: Are there any serious side effects?
A: Rarely, severe allergic reactions and corneal damage (with prolonged use) can occur.
Q6: What are the contraindications?
A: Known hypersensitivity to any component of the formulation.
Q7: Can it be used in children?
A: Yes, but with careful observation and accurate dosing due to increased potential for systemic absorption.
Q8: Does it interact with other medications?
A: It may interact with drugs metabolized by cholinesterases or those that prolong the QT interval. Inform patients to disclose all medications they take.
Q9: How long does the anesthetic effect last?
A: Typically, anesthesia onsets within 30 seconds and lasts for 15-20 minutes.
Q10: What precautions should be taken after administration?
A: Patients should avoid rubbing or touching the eye until the anesthetic effect wears off. Driving or operating machinery may be affected by temporarily blurred vision.
