The local anesthetics are compounds which produce reversible loss of sensation by preventing or diminishing the conduction of sensory nerve impulses near to the site of their application or injection. Local anesthetics could also be described as local analgesics as they are most often used to produce loss of pain without loss of nervous control. Also because their mode of action is to decrease permeability of the nerve cell membrane to sodium ions they are considered to have a membrane stabilizing effect.

Local anesthetics are used very widely in dental practice, for brief and superficial interventions for obstetric procedures, and for specialized techniques of regional anesthesia calling for highly developed skins. Where patient cooperation is required the patient must be psychologically prepared to adopt the proposed procedure. Facilities and equipment for resuscitation should be readily available at all times. Care must always be taken to avoid inadvertent intravascular injection.

The drugs used vary widely in their potency, toxicity, duration of action, stability in water, and ability to penetrate mucous membranes. These variations determine their suitability for use by various routes, e.g. topical (surface), infiltration, plexus, epidural (extradural) or spinal block.

The cold sensation produced by ethyl chloride spray is used to test the onset of regional anaesthesia.

Local infiltration anesthesia. Many simple surgical procedures that neither involve the body cavities nor require muscle relaxation can be performed under local infiltration anesthesia. Lower segment caesarean section can also be performed under local infiltration anesthesia. The local anesthetic drug of choice is lidocaine 0.5 % with or without epinephrine. No more than 4 mg/Kg of plain lidocaine or 7 mg/kg of lidocaine with epinephrine should be administered on any one occasion. The addition of epinephrine (adrenaline) diminishes local blood flow, slows the rate of absorption of the local anesthetic, and prolongs its effect. Care is necessary when using epinephrine for this purpose since, in excesses, it may produce ischaemic necrosis.

Surface anesthesia. Topical preparations of lidocaine are available and topical eye drop solutions of tetracaine are used for local anaesthesia of the cornea and conjunctiva.

Regional Block. A regional nerve block can proceed safe and effective anesthesia but its execution requires considerable training and practice. Nevertheless, where the necessary skills are available, techniques such as axillary’s or ankle block can be invaluable. Either lidocaine 1 % or bupivacaine 0.5 % is suitable. Bupivacaine has the advantage of a longer duration of action.

Spinal Anesthesia. This is one of the most useful of all anaesthetic techniques and can be used widely for surgery of the abdomen and the lower limbs. It is a major procedure requiring considerable training and practice. Either lidocaine 5 % in glucose or bupivacaine 0.5 % in glucose can be used but the latter is often chosen because of its longer duration of action.

Ethyl Chloride
Spray, 50ml

Indications: - as a local anaesthetic in minor operative procedures such as incision of boils and removal of localized growths.

Cautions: - during application, the skin adjacent to the area being treated should be covered with vaseline to protect against tissue sloughing. Inhalation of ethyl chloride should be avoided.

Contraindications: broken skin or mucous membrane.

Side effects: - freezing may injure cells, decrease resistance to infections, and delay healing. The frozen tissue may be painful, as it gets warm. And cutaneous sensitization may occur rarely.

Dose and Administration: - the container should be held about 12 inches (30 cm) from the area being treated and the spray directed downward until light frosting appears. Because the local anaesthetic effect is very brief, incision should be made as soon as the tissue become white.

Storage: - at room temperature, in tight containers, away from fire. Protect from light.

Lidocaine Hydrochloride
Ointment, 5 % in 10 g; Jelly, 2% in 30 ml; Cartridge, 2% in 1.8 ml ampoule; Spray, 4 %, 10 % in 80 g; Viscous, 2 % in 100 ml; Injection, 0.5 %, 1 %, 2 % in 2 and 20 ml vials; Injection Heavy, 5 % in 2 ml ampoule

Indications: - surface anaesthesia of mucous membranes; infiltration anesthesia; peripheral and sympathetic nerve block; dental anaesthesia; spinal anaesthesia; intravenous regional anaesthesia; arrhythmias.

Cautions: - caution in patients with inflammation and/or infections at site of injection, and in very young, the elderly acutely ill, or weak patients.

Drug interactions: - avoid simultaneous use of lidocaine with vasoconstrictors (e.g. adrenaline) on the extremities such as the finger, toes…etc.

Contraindications: known hypersensitivity.

Side effects: a transient burning sensation may occur at the site of injection.

Dose and Administration:

Note: - Intradermally, subcutaneously, or submucosally (local infiltration). Inject indirectly in to the tissue to be incised or in the immediate area surgery. It should be injected slowly, with frequent aspirations before and during the injection, to reduce the risk of inadvertent intravascular administration.

The total dose should not exceed 300mg/dose (4.5mg/kg of body weight). Children should receive smaller amounts of lidocaine, generally in lower concentration than adults.

By injection, infiltration anesthesia, according to patient’s weight and nature of procedure, max, 300 mg,

Ointment, Topical, adult and child 2 years of age and older as a 5 % ointment, to the affected area three or four times a day as needed.

Jelly, Topical, Adult, to the affected area three or four times a day as needed

Spray, Topical, Adult, sprayed and/or applied to affected area three or four times a day as needed.

Storage: - at room temperature. Protect from freezing.

Lidocaine Hydrochloride and Adrenaline
Injection, 1 % + 1:200,000 in 30 ml Vial
Injection, 2 % + 1:200,000 in 20 ml vial

See under Lidocaine Hydrochloride

Dose and Administrations

Dental Anesthesia (for infiltration or nerve block)

Adult, 20 to 100 mg (1 to 5 ml) of lidocaine hydrochloride as 2 % solution with epinephrine 1:2000,000; Child, 4 to 5 mg of Lidocaine Hydrochloride per kg of body weight or 100 to 150 mg as a single dose.

Local infiltration or nerve block 7 mg of lidocaine hydrochloride per kg of body weight as a 0.25 to 1 % solution with epinephrine 1:200,000.

Storage: - at room temperature protect from light and freezing.