Composition
Each 1 ml contains:
Benoxinate hydrochloride ........................................................ 4 mg
Inactive ingredients:
Sodium chloride, hydroxypropyl methylcellulose, citric acid anhydrous, thimerosal, water for injection.
Therapeutic Indications
As a topical ocular anaesthetic.
Dosage and Administration
Adults (including the Elderly) and Children:
One drop is sufficient when dropped into the conjunctival sac to anaesthetise the surface of the eye to allow tonometry after one minute.
A further drop after 90 seconds provides adequate anaesthesia for the fitting of contact lenses.
Three drops at 90 second intervals provides sufficient anaesthesia for a foreign body to be removed from the corneal epithelium or for incision of a meibomian cyst through the conjunctiva.
Corneal sensitivity is normal again after about one hour.
Instill dropwise into the eye according to the recommended dosage.
Each BENOX unit should be discarded after use.
Contraindications
Not to be used in patients with a known hypersensitivity to the product.
Warnings and Precautions
Transient stinging and blurring of vision may occur on instillation.
The anaesthetised eye should be protected from dust and bacterial contamination.
When applied to the conjunctiva, benoxinate is less irritant than amethocaine in normal concentrations.
The cornea may be damaged by prolonged application of anaesthetic eye drops.
Systemic absorption may be reduced by compressing the lacrimal sac at the medial canthus for a minute during and following the instillation of the drops. (This blocks the passage of the drops via the naso-lacrimal duct to the wide absorptive area of the nasal and pharyngeal mucosa. It is especially advisable in children).
Pregnancy and Lactation
BENOX should not be used in pregnancy or lactation, unless considered essential by the physician.
Effects on ability to drive and to use machines
Patients should be advised not to drive or operate hazardous machinery until normal vision is restored.
Undesirable Effects
Transient stinging and blurring of vision may occur on instillation.
Overdose
Overdose following the recommended use is unlikely.
Pharmacological Properties
Pharmacodynamic properties:
Benoxinate hydrochloride is used as a local anaesthetic as it reversibly blocks the propagation and conduction of nerve impulses along nerve axons.
Pharmacokinetic properties:
The rate of loss of local anaesthetics through tearflow is very high as they induce an initial stinging reaction which stimulates reflex lacrimation and leads to dilution of the drugs.
It is thought that this is responsible for the very short duration of maximum effect of local anaesthetics.
The non-ionised base of benoxinate is rapidly absorbed from the pre-corneal tear film by the lipophilic corneal epithelium.
The drug then passes into the corneal stroma and from there into the anterior chamber where it is carried away by the aqueous flow and diffuses into the blood circulation in the anterior uvea.
As with other ester type local anaesthetics, benoxinate is probably rapidly metabolised by plasma cholinesterases (and also by esterases in the liver).
Storage
Store at a temperature not exceeding 30°C. It should be used within 28 days after opening.
Packaging
BENOX Sterile Ophthalmic Solution: 10 ml Plastic dropper bottle.