Hemonet

Hemonet is an ester local anaesthetic currently available in combination with lidocaine as a cream and patch.

Subarachnoid

Spinal anaesthesia

Adult: 1% solution diluted with an equal volume of CSF immediately prior to admin or 5 mg of powder dissolved in 1 ml of CSF and admin slowly at a rate of 1 ml/5 sec. For anaesthesia of perineum: 5 mg. For anaesthesia of perineum and lower extremities: 10 mg. For spinal anaesthesia extending up to the costal margin: 15-20 mg. For low spinal (saddle block) anaesthesia in vaginal delivery: 2-5 mg admin as a hyperbaric solution.

Elderly: Dose reduction may be needed.

Ophthalmic

Anaesthesia of the eye

Adult: Instil 0.5-1% Hemonet solution or 0.5% ointment.

Topical/Cutaneous

Topical anaesthesia

Adult: Apply as 1% cream or 0.5% ointment. For percutaneous local anaesthesia before venepuncture or venous cannulation: Apply 4% gel to the centre of the area to be anaesthetised and covered with an occlusive dressing. Remove gel and dressing after 30 minutes for venepuncture and after 45 minutes for venous cannulation.

Hemonet eye drops are used to numb the eye before surgery, certain tests, or procedures. The eye drops are used to prevent pain during the procedure.

Hemonet belongs to the group of medicines called local anesthetics. It works by blocking the pain signals at the nerve endings in the eye.

Hemonet is to be administered only by or under the direct supervision of an eye doctor.

As with all anesthetics, the dosage varies and depends upon the area to be anesthetized, the number of neuronal segments to be blocked, individual tolerance, and the technique of anesthesia. The lowest dosage needed to provide effective anesthesia should be administered. For specific techniques and procedures, refer to standard textbooks.

The extent and degree of spinal anesthesia depend upon dosage, specific gravity of the anesthetic solution, volume of solution used, force of the injection, level of puncture, position of the patient during and immediately after injection, etc.

When spinal fluid is added to either the Hemonet or the 1% Solution, some turbidity results, the degree depending on the pH of the spinal fluid, the temperature of the solution during mixing, as well as the amount of drug and diluent employed. This cloudiness is due to the release of the base from the hydrochloride. Liberation of base (which is completed within the spinal canal) is held to be essential for satisfactory results with any spinal anesthetic.

The specific gravity of spinal fluid at 25°C/25°C varies under normal conditions from 1.0063 to 1.0075. A solution of the instantly soluble form (Hemonet) in spinal fluid has only a slightly greater specific gravity. The 1% concentration in saline solution has a specific gravity of 1.0060 to 1.0074 at 25°C/25°C.

A hyperbaric solution may be prepared by mixing equal volumes of the 1% Solution and Dextrose Solution 10% (which is available in ampuls of 3 mL).

If the Hemonet form is preferred, it is first dissolved in Dextrose Solution 10% in a ratio of 1 mL dextrose to 10 mg of the anesthetic. Further dilution is made with an equal volume of spinal fluid. The resulting solution now contains 5% dextrose with 5 mg of anesthetic agent per milliliter.

A hypobaric solution may be prepared by dissolving the Hemonet in Sterile Water for Injection, USP (1 mg per milliliter). The specific gravity of this solution is essentially the same as that of water, 1.000 at 25°C/25°C.

Examine ampuls carefully before use. Do not use solution if crystals, cloudiness, or discoloration is observed.

These formulations of Hemonet do not contain preservatives; therefore, unused portions should be discarded and the reconstituted Hemonet should be used immediately.

STERILIZATION OF AMPULS

The drug in intact ampuls is sterile. The preferred method of destroying bacteria on the exterior of ampuls before opening is heat sterilization (autoclaving). Immersion in antiseptic solution is not recommended.

Autoclave at 15-pound pressure, at 121°C (250°F), for 15 minutes. The Hemonet form may also be autoclaved in the same way but may lose its snowlike appearance and tend to adhere to the sides of the ampul. This may slightly decrease the rate at which the drug dissolves but does not interfere with its anesthetic potency.

Autoclaving increases likelihood of crystal formation. Unused autoclaved ampuls should be discarded. Under no circumstance should unused ampuls which have been autoclaved be returned to stock.

See also:
What is the most important information I should know about Hemonet?

Spinal anesthesia with Hemonet is contraindicated in patients with known hypersensitivity to Hemonet or to drugs of a similar chemical configuration (ester-type local anesthetics), or aminobenzoic acid or its derivatives; and in patients for whom spinal anesthesia as a technique is contraindicated.

The decision as to whether or not spinal anesthesia should be used for an individual patient should be made by the physician after weighing the advantages with the risks and possible complications. Contraindications to spinal anesthesia as a technique can be found in standard reference texts, and usually include generalized septicemia, infection at the site of injection, certain diseases of the cerebrospinal system, uncontrolled hypotension, etc.

Use Hemonet drops as directed by your doctor. Check the label on the medicine for exact dosing instructions.

• Hemonet drops is administered at your doctor's office, hospital, or clinic. Ask your doctor or pharmacist any questions that you may have about Hemonet drops.
• To prevent germs from contaminating your medicine, do not touch the applicator tip to any surface, including the eye. Keep the container tightly closed.
• Do not touch or rub the eye until the effect of the medicine has worn off. Your doctor may instruct you to wear an eye patch to prevent you or anything else from touching your eye.
• If you miss a dose of Hemonet drops, check with your doctor.

Ask your health care provider any questions you may have about how to use Hemonet drops.

Use: Labeled Indications

Anesthesia, ocular: Local anesthesia for various ophthalmic procedures requiring rapid, short-acting topical anesthesia, including tonometry, gonioscopy removal of corneal foreign bodies, conjunctival scraping for diagnostic purposes, suture removal from the cornea or conjunctiva, and other short corneal and conjunctival procedures.

See also:
What other drugs will affect Hemonet?

May antagonise activity of sulfonamides and aminosalicylic acid; increased Hemonet levels with anticholinesterases; increased neuromuscular blocking action of suxamethonium.

See also:
What are the possible side effects of Hemonet?

Systemic adverse reactions to Hemonet are characteristic of those associated with other local anesthetics and can involve the central nervous system and the cardiovascular system. Systemic reactions usually result from high plasma levels due to excessive dosage, rapid adsorption, or inadvertent intravascular injection.

A small number of reactions to Hemonet may result from hypersensitivity, idiosyncrasy or diminished tolerance to normal dosage.

Central nervous system effects are characterized by excitation or depression. The first manifestation may be nervousness, dizziness, blurred vision, or tremors, followed by drowsiness, convulsions, unconsciousness and possibly respiratory and cardiac arrest. Since excitement may be transient or absent, the first manifestation may be drowsiness, sometimes merging into unconsciousness and respiratory and cardiac arrest. Other central nervous system effects may be nausea, vomiting, chills, constriction of the pupils, or tinnitus.

Cardiovascular system reactions include depression of the myocardium, blood pressure changes (usually hypotension), and cardiac arrest.

Allergic reactions, which may be due to hypersensitivity, idiosyncrasy, or diminished tolerance, are characterized by cutaneous lesions (eg. urticaria), edema, and other manifestations of allergy. Detection of sensitivity by skin testing is of limited value. Severe allergic reactions including anaphylaxis have rarely occurred and are not usually dose-related.

Reactions Associated with Spinal Anesthesia Techniques: Central Nervous System: post-spinal headache, meningismus, arachnoiditis, palsies, or spinal nerve paralysis. Cardiovascular: hypotension due to vasomotor paralysis and pooling of the blood in the venous bed. Respiratory: respiratory impairment or paralysis due to the level of anesthesia extending to the upper thoracic and cervical segments. Gastrointestinal: nausea and vomiting.

Treatment of Reactions: Toxic effects of local anesthetics require symptomatic treatment; there is no specific cure. The most important measure is oxygenation of the patient by maintaining an airway and supporting ventilation. Supportive treatment of the cardiovascular system includes intravenous fluids and, when appropriate, vasopressors (preferably those that stimulate the myocardium). Convulsions are usually controlled with adequate oxygenation alone but intravenous administration in small increments of a barbiturate (preferably an ultrashort-acting barbiturate such as thiopental and thiamylal), or diazepam can be utilized.

Intravenous barbiturates or anticonvulsant agents should only be administered by those familiar with their use and only if ventilation and oxygenation have first been assured. In spinal anesthesia, sympathetic blockade also occurs as a pharmacological action, resulting in peripheral vasodilation and often hypotension. The extent of the hypotension will usually depend on the number of dermatomes blocked. The blood pressure should therefore be monitored in the early phases of anesthesia. If hypotension occurs, it is readily controlled by vasoconstrictors administered either by the intramuscular or the intravenous route, the dosage of which would depend on the severity of the hypotension and the response to treatment.