Related Experiment Video
Updated: May 12, 2026
06:19
Intracameral Injection in Rats with Low Risk of Adverse Effects
Published on: May 31, 2024
Topical drug formulations for prolonged corneal anesthesia
Liqiang Wang1, Sahadev A Shankarappa, Rong Tong
1Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.
Cornea
|April 26, 2013
Summary
Tetrodotoxin (TTX) combined with proparacaine (PPC) significantly extended corneal anesthesia duration in rats. However, this combination moderately delayed corneal healing, suggesting cautious use for prolonged anesthesia.
Area of Science:
- Ophthalmology
- Pharmacology
- Neuroscience
Background:
- Current ocular local anesthetics have short durations and impede corneal healing.
- There is a need for longer-acting corneal anesthesia suitable for extended use.
Purpose of the Study:
- To investigate the effect of tetrodotoxin (TTX), a sodium channel blocker, on corneal anesthesia duration.
- To evaluate TTX in combination with proparacaine (PPC) or octyl-trimethyl ammonium bromide (OTAB) for corneal anesthesia.
- To assess the impact of these combinations on corneal healing.
Main Methods:
- Topical application of TTX, PPC, and OTAB to rat corneas.
- Measurement of corneal sensitivity via blink response using a Cochet-Bonnet esthesiometer.
- In vivo study of corneal epithelialization rates after debridement.
Main Results:
- Combining TTX and PPC extended corneal anesthesia 8-10 times longer than individual drugs.
- OTAB did not prolong corneal anesthesia.
- TTX and PPC combination moderately delayed corneal epithelialization.
Conclusions:
- Coadministration of TTX and PPC offers prolonged corneal anesthesia.
- Delayed corneal reepithelialization necessitates caution when using this combination for extended periods.
Related Concept Videos
01:23Local Anesthetics: Common Agents and Their Applications
Local anesthetics (LAs) are commonly used for various applications in medical and dental procedures. Some of the common agents used are cocaine, lidocaine, and bupivacaine.
Cocaine is an ester of benzoic acid and methylecgogine. It is used to anesthetize and vasoconstrict locally. Currently, it is used primarily for topical applications. It is beneficial for surgeries on the upper respiratory tract, providing anesthesia and shrinking the mucosa. Cocaine in the form of cocaine hydrochloride is...
Cocaine is an ester of benzoic acid and methylecgogine. It is used to anesthetize and vasoconstrict locally. Currently, it is used primarily for topical applications. It is beneficial for surgeries on the upper respiratory tract, providing anesthesia and shrinking the mucosa. Cocaine in the form of cocaine hydrochloride is...
01:23Ophthalmic Drug Delivery Systems
Ophthalmic drug delivery faces major limitations due to poor absorption across the corneal membrane. This process is primarily driven by diffusion and is influenced by two main factors: the physicochemical properties of the drug and tear drainage. Most ophthalmic drugs, such as pilocarpine, epinephrine, atropine, and local anesthetics, are weak bases. They are typically formulated at an acidic pH to enhance chemical stability. However, this leads to high ionization, reducing their ability to...
01:30Local Anesthetics: Clinical Application as Surface, Infiltration, and Conduction Block Anesthesia
Depending on the target organ, local anesthetics (LAs) can be administered via various routes. In surface anesthesia, LAs are applied directly to the surface of the skin or mucous membranes. It is widely used for topical skin numbing before venipuncture or minor surgical procedures. Commonly used surface local anesthetics are lidocaine or benzocaine sprays or creams. Surface anesthesia occurs within 5 minutes and lasts for about 60 minutes. One of the main disadvantages of topical anesthesia is...
01:22Drug Delivery: Miscellaneous Routes
Drug delivery methods like oral inhalation, nasal sprays, transdermal patches, eye drops, intravitreal injection, and rectal administration provide localized effects with reduced toxicity.
Oral inhalation and nasal sprays swiftly transfer drugs across the respiratory epithelium's mucosal layer. Inhaled glucocorticoids and bronchodilators directly target lung conditions such as asthma, while fluticasone nasal spray mitigates allergic rhinitis.
Transdermal patches transport drugs through the...
Oral inhalation and nasal sprays swiftly transfer drugs across the respiratory epithelium's mucosal layer. Inhaled glucocorticoids and bronchodilators directly target lung conditions such as asthma, while fluticasone nasal spray mitigates allergic rhinitis.
Transdermal patches transport drugs through the...
01:13Local Anesthetics: Pharmacokinetics
The potency and duration of action of local anesthetics (LAs) are determined by their pharmacokinetics. Pharmacokinetics describes how LAs are absorbed, distributed, metabolized, and eliminated from the body. When administered to the vascular tissues, LAs are quickly absorbed and enter the systemic circulation, reducing their localized effects. Adding vasoconstrictors such as epinephrine to LAs reduces their absorption into the systemic circulation, making them clinically effective. The...
01:30Local Anesthetics: Chemistry and Structure-Activity Relationship
Local anesthetics (LAs) are drugs that induce a temporary loss of sensation in a limited body area, preventing pain. Cocaine was the first local anesthetic discovered in the late 19th century. Cocaine is a benzoic acid ester obtained from the leaves of coca shrubs and was often used for its psychotropic effects. Cocaine was first isolated in 1860 by Albert Niemann. Sigmund Freud studied the physiological actions of cocaine. Carl Koller later introduced it into clinical practice in 1884 as a...