Humacain (Oxybuprocaine Hydrochloride)

Humacain is indicated for temporary loss of sensation on the surface of the eye to aid clinical evaluation, diagnostic testing, and minor interventions performed by eye care professionals.

• Topical ocular anesthesia for routine slit‑lamp examinations.
• Anesthesia for corneal sensitivity testing.
• Preparation of the ocular surface before minor surgical procedures such as foreign‑body removal.
• Use during laser procedures that require brief corneal numbing.
• Facilitation of intra‑ocular pressure measurements that may cause discomfort.
• Application prior to conjunctival biopsy to ensure patient comfort.

• Oxybuprocaine hydrochloride exerts its anesthetic effect by reversibly binding to voltage‑gated sodium channels on neuronal membranes in the corneal and conjunctival epithelium. This blockade prevents the influx of sodium ions during depolarization, thereby inhibiting the generation and propagation of nerve impulses. The result is a rapid, localized loss of sensation that lasts for several minutes, after which normal nerve function resumes as the drug is metabolized.

Adverse reactions to Humacain are generally mild and transient, but rare serious events have been reported.

Common

• Temporary stinging or burning sensation upon instillation.
• Mild conjunctival hyperemia (redness).
• Transient blurred vision lasting a few minutes.
• Slight increase in tear production.
• Mild eyelid edema that resolves spontaneously.
• Temporary decrease in visual acuity due to corneal surface anesthesia.

Serious

• Allergic contact keratitis with epithelial defects.
• Corneal ulceration or epithelial breakdown.
• Persistent ocular pain beyond the expected anesthetic period.
• Severe hypersensitivity reaction such as angioedema of the eyelid.
• Irreversible corneal scarring in cases of prolonged exposure.
• Systemic toxicity such as central nervous system depression, although extremely rare.

When using Humacain, clinicians should observe specific precautions to minimize risk and ensure safe application.

• Verify patient has no known hypersensitivity to oxybuprocaine or other ester‑type anesthetics.
• Avoid administration in eyes with active infection, severe inflammation, or epithelial defects.
• Limit the number of applications to the recommended frequency to prevent corneal toxicity.
• Use caution in patients with a history of allergic eye disease or atopic keratoconjunctivitis.
• Do not combine with other topical ophthalmic agents unless directed by a physician.
• Ensure proper aseptic technique to reduce the risk of contamination.

Humacain may interact with other ophthalmic medications or systemic agents, influencing its anesthetic effect or safety profile.

Avoid

• Concurrent use with other topical anesthetics, which can increase the risk of corneal toxicity.
• Administration together with mydriatic agents that may exacerbate ocular irritation.
• Do not apply immediately after ocular surgery where the corneal epithelium is compromised.

Use with caution

• Combination with anti‑inflammatory eye drops; monitor for delayed wound healing.
• Use alongside systemic medications that lower seizure threshold, although systemic absorption is minimal.
• Co‑administration with preservative‑containing solutions; consider preservative‑free formulations to reduce irritation.
• When used with contact lenses, remove lenses before application and wait sufficient time before reinsertion.