From the Research
Proparacaine has a half-life of approximately 15-20 minutes in the eye, as supported by the most recent and highest quality study available 1. This topical anesthetic, commonly used in ophthalmology, provides rapid onset of action (within 20 seconds) with anesthetic effects typically lasting about 15 minutes. The short half-life explains why proparacaine's effects are relatively brief compared to other ocular anesthetics. After application, proparacaine is metabolized by plasma esterases, which break down the ester linkage in the drug molecule. This rapid metabolism contributes to its short duration of action. Some key points to consider when using proparacaine include:
- Rapid onset of action and short duration of effects, making it suitable for quick diagnostic procedures
- Metabolism by plasma esterases, which contributes to its short half-life
- Potential benefits in clinical settings, such as minimizing prolonged corneal epithelial exposure
- Importance of advising patients not to rub their eyes while the cornea is anesthetized to avoid potential damage The brief half-life is actually beneficial in clinical settings as it allows for quick diagnostic procedures while minimizing prolonged corneal epithelial exposure that could delay healing or increase risk of corneal damage, as seen in studies comparing proparacaine to other anesthetics 2, 1. Patients should be advised not to rub their eyes while the cornea is anesthetized, as they may inadvertently cause damage without feeling pain due to the anesthetic effect, even though the drug is being cleared from the tissue relatively quickly. In terms of specific studies, a 2021 study found that 0.5% proparacaine drops were effective in providing anesthesia for intravitreal injections, with no significant difference in pain scores compared to 3.5% lidocaine gel 1. Another study from 2013 found that a single drop of 0.5% proparacaine hydrochloride was comparable to intracameral supplementation of preservative-free xylocaine for phacoemulsification in uncomplicated cataract surgery 2. Overall, the available evidence suggests that proparacaine has a half-life of approximately 15-20 minutes in the eye, making it a suitable choice for quick diagnostic procedures and minimizing prolonged corneal epithelial exposure.