WHO Model Prescribing Information: Drugs Used in Anaesthesia
(1989; 60 pages) [French] View the PDF document
Table of Contents
View the documentPreface
View the documentIntroduction
Open this folder and view contentsPremedication
Open this folder and view contentsGeneral anaesthetics and oxygen
Close this folderLocal anaesthetics
View the documentBupivacaine
View the documentLidocaine
View the documentTetracaine
View the documentEpinephrine (for use with local anaesthetics)
Open this folder and view contentsNon-opioid analgesics
Open this folder and view contentsOpioid analgesics and antagonists
Open this folder and view contentsMuscle relaxants and cholinesterase inhibitors
Open this folder and view contentsBlood substitutes
Open this folder and view contentsSolutions for correcting water and electrolyte imbalance
Open this folder and view contentsAntacid for use in obstetric practice
View the documentAnaesthesia at the District Hospital
View the documentSelected WHO publications of related interest
View the documentBack cover
 

Lidocaine

Group: local anaesthetic agent
Injection (hydrochloride): 5 mg/ml (0.5%), 10 mg/ml (1%) in 20-ml ampoule; 10 mg/ml (1%) + epinephrine 5 micrograms/ml (1:200 000) in 20-ml ampoule; 20 mg/ml (2%) + epinephrine 12.5 micrograms/ml (1:80 000) in 2.2-ml cartridge for dental anaesthesia; 50 mg/ml (5%) in 2-ml ampoule to be mixed with 75 mg/ml (7.5%) glucose solution
Topical forms: 20-40 mg (hydrochloride)/ml (2-4%) as gel or solution

General information

Lidocaine is a moderately long-acting local anaesthetic. It blocks initiation and transmission of nerve impulses at the site of application by stabilizing the neuronal membrane. The compound is ultimately metabolized in the liver. Anaesthesia, which persists for 1-3 hours, is induced within 1-5 minutes following mucosal application, infiltration and spinal or dental nerve block, and within 10-15 minutes following other methods of administration.

Clinical information

Uses

• Surface anaesthesia of mucous membranes.
• Infiltration anaesthesia.
• Peripheral and sympathetic nerve block.
• Dental anaesthesia.
• Spinal anaesthesia.
• Intravenous regional anaesthesia.
• Epidural and caudal anaesthesia (these techniques produce prolonged regional anaesthesia and should be attempted only by experienced specialist anaesthetists).

Dosage and administration

The aim is to administer the smallest effective dose. This varies with the procedure adopted, the degree of anaesthesia required, the rate of absorption from the injection site and the size and responsive-ness of the patient. Higher initial blood levels are attained with more concentrated solutions.

Solutions are available with or without epinephrine at 5 micrograms/ml (1:200000) or, for dental anaesthesia, 12.5 micrograms/ml (1:80 000). Epinephrine is contraindicated for ring block of digits or the penis and for other procedures associated with risk of ischaemia.

The maximum cumulative safe doses of lidocaine for adults and children are:

0.5%, 1 % lidocaine

4 mg/kg

0.5%, 1 % lidocaine + epinephrine 5 μg/ml (1:200 000)

7 mg/kg.

Anaesthetic procedure

Concentration (%)

Epinephrine

Dose

     

ml

mg

Local infiltration and peripheral nerve block

0.5

No

<50

<250

 

1.0

No

<25

<250

 

0.5

Yes

<80

<400

 

1.0

Yes

<40

<400

Surface anaesthesia

       
 

Pharynx, larynx, trachea

4

No

1-5

40-200

 

Urethra

4

No

10

400

Dental anaesthesia

2

Yes

1-5

20-100

Spinal anaesthesia

5
(+ 7.5% glucose)

No

1-1.5

50-75

The table provides a general guide to dosage in adults. Smaller dosages should be administered to debilitated, elderly, epileptic and acutely ill patients.

Solutions containing preservatives should not be used for spinal, epidural, caudal and intravenous regional anaesthesia.

Spinal anaesthesia

Spinal anaesthesia should only be attempted by a person trained in the technique and competent to treat possible complications. A “heavy” solution (5% lidocaine in 7.5% glucose) will provide the muscular relaxation required for abdominal surgery. Full aseptic technique must be employed for the injection and the pa dent must be appropriately tilted to ensure safety and the required level of analgesia.

Spinal anaesthesia always causes hypotension as a result of sympathetic blockade. It should never be used in patients with any condition resulting in hypovolaemia. The hypotensive response may largely be averted by preliminary intravenous infusion of 500-1000 ml of physiological saline (9 mg/ml) but blood pressure should always be measured every 2 minutes for at least 10 minutes. Postoperative headache can be prevented by instructing the patient to remain supine for 24 hours.

Obstetric practice

Lumbar epidural block has largely replaced caudal epidural block for relief of pain in labour. It requires less local anaesthetic, carries less risk of infection and is readily extended should caesarean section become necessary. However, because of the risk to both the mother and the fetus, it should be attempted only by an experienced specialist anaesthetist. Maternal blood pressure, fetal heart rate and uterine contractions should be monitored throughout the procedure. Paracervical block is no longer recommended during labour because it results in very high levels of the drug in fetal blood.

Contraindications

• Known or suspected hypersensitivity to lidocaine.

• Skin infection adjacent to the proposed site of injection, concomitant anticoagulant therapy or an abnormal bleeding tendency.

• Severe anaemia or heart disease.

• Spinal and epidural anaesthesia should never be used in dehydrated or hypovolaemic patients.

Precautions

Facilities and equipment for resuscitation should be readily available at all times.

Assurance must be obtained that the patient is psychologically prepared to accept the proposed procedure.

Caution is required in patients with hepatic impairment when the dosage or route of administration is liable to result in high blood levels.

Care must always be taken to avoid inadvertent intravascular injection.

Use in pregnancy

Safe use in early pregnancy has not been established. However, there is no clinical evidence to suggest that exposure of the mother to lidocaine is harmful to the fetus.

Adverse effects

These may result from excessive dosage, inadvertent intravascular injection or injection into highly vascular tissues. Initial signs of light-headedness, dizziness, blurred vision, restlessness, tremors and, occasionally, convulsions are rapidly followed by drowsiness, unconsciousness and respiratory failure. Myocardial depression and hypotension may result in hypoxia, acidosis, heart block and cardiac arrest.

Hypersensitivity and allergic reactions may also occur.

Epidural anaesthesia is occasionally complicated by urinary retention, faecal incontinence, headache, backache or loss of perineal sensation. Transient paraesthesiae and paraplegia are very rare complications.

Drug interactions

Co-administration of oxytocic drugs postpartum may cause severe and prolonged hypertension. The use of lidocaine preparations containing epinephrine during or following the administration of halothane or trichloroethylene creates a risk of cardiac dysrhythmias.

Overdosage

Overdosage or accidental intravascular injection is characterized by the systemic effects described above. Treatment is symptomatic. There is no specific antidote. A clear airway should be maintained and ventilation assisted as required. Convulsions may be controlled with diazepam or thiopental.

Storage

Lidocaine injection should be kept protected from light and should not be allowed to freeze. Methylene blue may be added to topical formulations for ease of identification.

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