BENOXINATE HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BENOXINATE HYDROCHLORIDE (BENOXINATE HYDROCHLORIDE).
Sodium channel blocker; stabilizes neuronal membrane and prevents initiation and transmission of nerve impulses.
| Metabolism | Hydrolyzed by plasma esterases |
| Excretion | Primarily renal; approximately 70-80% excreted unchanged in urine; minor biliary/fecal elimination (<10%) |
| Half-life | 2.5-3.5 minutes in plasma; extremely short half-life due to rapid hydrolysis by plasma esterases, limiting systemic exposure after ocular administration |
| Protein binding | Moderate; approximately 55-65% bound to plasma proteins (primarily albumin); binding is reversible |
| Volume of Distribution | Not established for systemic absorption due to minimal systemic levels after topical use; expected to be small (approximately 0.1-0.2 L/kg) as a local anesthetic with limited distribution |
| Bioavailability | Not applicable for topical ophthalmic route (local effect); negligible systemic bioavailability (<5%) due to rapid hydrolysis in plasma and minimal absorption across cornea |
| Onset of Action | Topical ophthalmic: within 30 seconds; duration of corneal anesthesia sufficient for tonometry and minor procedures |
| Duration of Action | Corneal anesthesia lasting 15-20 minutes after topical application; sufficient for short diagnostic procedures; use limited to avoid epithelial toxicity with prolonged exposure |
1-2 drops of 0.4% solution in the conjunctival sac up to every 5-10 minutes for surface anesthesia, not exceeding 7 doses per procedure.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required; drug is minimally absorbed systemically and renally cleared. |
| Liver impairment | No specific guidelines; use with caution in severe hepatic impairment due to potential systemic accumulation from ocular absorption. |
| Pediatric use | Not recommended for use in children; safety and efficacy not established. |
| Geriatric use | No specific dose adjustment; use lowest effective dose due to increased risk of corneal toxicity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BENOXINATE HYDROCHLORIDE (BENOXINATE HYDROCHLORIDE).
| Breastfeeding | It is not known whether benoxinate hydrochloride is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when administered to a nursing woman. The M/P ratio is not available. |
| Teratogenic Risk | No adequate and well-controlled studies in pregnant women. In animal studies, no evidence of teratogenicity was observed at doses up to 40 mg/kg/day (approximately 0.5 times the maximum recommended human ophthalmic dose on a mg/m² basis). However, caution is advised. The drug should be used during pregnancy only if clearly needed. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to ester-type anesthetics","Ocular infections or trauma with epithelial disruption"]
| Precautions | ["Prolonged use may cause corneal epithelial damage","Avoid contamination of dropper tip","Not for injection","Use with caution in patients with cardiac disease or hyperthyroidism"] |
| Food/Dietary | None known for ophthalmic use. No dietary restrictions. |
| Clinical Pearls | Benoxinate hydrochloride is a topical ophthalmic anesthetic used for short procedures. Onset within 1 minute, duration ~15 minutes. Prolonged use delays corneal epithelial healing and increases infection risk. Do not touch dropper tip to eye. Discard solution if discolored. Contraindicated in patients with hypersensitivity to ester-type anesthetics. |
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| Fetal Monitoring | No specific monitoring is required other than standard pregnancy monitoring. Observe for maternal ocular side effects. |
| Fertility Effects | No studies have been conducted to evaluate the effects of benoxinate hydrochloride on fertility. No evidence of impaired fertility was observed in animal reproduction studies. |
| Patient Advice | Temporary stinging or burning upon instillation is common. · Avoid rubbing eyes until numbness wears off to prevent corneal injury. · Do not touch dropper tip to any surface to avoid contamination. · Vision may be temporarily blurred; avoid driving until clear. · Seek medical attention if eye pain, redness, or vision changes occur after use. · Do not use for prolonged periods or without medical supervision. |