Benoxinate
Medication Facts
- Performance enhancing
- No
- Total hours to clear
- Not recorded
- Frequently used
- Most Prescribed
- ESC ID
- BENOXI-0105
- Trade names
- Not recorded
- Drug type
- Local anesthetic
- Plasma half-life · hours
- Unmeasurable
- Equine dosing
- Consult Veternarian, **Eye/Cornea pain relief**
- Cmax · peak plasma concentration
- Non-Published
- Tmax · time to peak plasma concentration
- I minute after drops
- ESC concentration guidance
- Eye drops absorbed within 1 minute after administration, and reaches CMAX in approximately 15 minues
- Primary withdrawal · hours
- 0
- Washout withdrawal · hours
- 0
- ESC control type
- A1 - Generally Controlled - Therapeutic
- Medication report required
- Generally not required, however understand exceptions.
Uses & side effects
Pain Relief Eyes, Anticeptic Drops
Product-specific side effects await source review.
Drug interactions
Applied directly to eye cornea - anestetic. Benoxinate (also known as oxybuprocaine) is a highly effective topical local anesthetic used off-label in equine medicine for ophthalmic procedures. It provides rapid, deep anesthesia to the horse's cornea, making it valuable for tonometry, removing foreign objects, or managing eye injuries.Because it is applied topically to the eye and acts locally, systemic drug interactions are exceedingly rare. However, its interactions are primarily functional, chemical, or regulatory rather than systemic:🔄 Functional & Diagnostic InteractionsFluorescein Sodium (Synergistic/Diagnostic): Benoxinate is frequently formulated directly with fluorescein sodium (a diagnostic stain used to identify corneal ulcers). The combination is highly effective because the benoxinate numbs the eye immediately, allowing the veterinarian to safely perform a thorough diagnostic look or use a Cochet-Bonnet esthesiometer to measure corneal sensitivity.Other Topical Anesthetics (Additive): Co-administering benoxinate with other topical anesthetics, such as proparacaine or tetracaine, provides an additive local numbing effect. However, this is rarely clinically indicated since benoxinate on its own achieves maximum corneal anesthesia (\(CTT = 0\)) within one minute. Stacking them increases the risk of local corneal epithelial toxicity.⚠️ Chemical & Antimicrobial ConsiderationsTopical Antibiotics (Physical/pH Compatibility): If a horse has a corneal ulcer or eye infection, veterinarians often administer topical antibiotics like tobramycin ophthalmic solution alongside an anesthetic. While there are no systemic interactions, the pH of the solutions matters. Administering multiple ophthalmic drops too close together can dilute the active ingredients or cause physical incompatibility in the tear film. Drops should be spaced at least 5 to 10 minutes apart.Sulfa-Based Antibiotics (Theoretical Inhibition): Benoxinate is an ester-type local anesthetic. In humans, ester anesthetics break down into para-aminobenzoic acid (PABA), which can theoretically antagonize and reduce the efficacy of sulfonamide (sulfa) antibiotics. While rare in topical ophthalmic applications for horses, care should be taken if a horse is on concurrent sulfa-based eye drops.🚫 Clinical & Regulatory RisksMasked Injury Progression: The primary "interaction" risk is behavioral. Because benoxinate temporarily eliminates the blink reflex and corneal pain sensitivity, a horse may inadvertently rub its eye against a stall wall or bucket, turning a minor scratch into a severe, complicated ulcer. The eye must be protected until the anesthesia wears off (typically 30–45 minutes).Competition and Drug Testing: Under governing bodies like the Equine Sports Council (ESC) and US Equestrian (USEF), local anesthetics are tightly regulated substances. Even though it is a topical drop, benoxinate can be absorbed systemically through the nasolacrimal duct and trigger a positive drug test. If a horse is competing, strict veterinary-calculated withdrawal times must be observed