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Lidocaine, 5 % ointment

Drug formSoft

ATC categoryStomatology

ATC subcategoryLocal anesthetics

Brand nameLidocaine

Generic nameLidocaine

Composition

Each gram contains:

active ingredient: lidocaine – 50 mg;

excipients: polyethylene glycol 400, polyethylene glycol 4000, propylene glycol, water purified.

Pharmacological group and ATC code
Local anaesthetic; N01BB02.
Chemical name and CAS number
2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide; 137-58-6.
Pharmacology

Lidocaine is a local anesthetic of the amide type with actions. Lidocaine is a useful surface anesthetic but it may be rapidly and extensively absorbed following topical application to mucous membranes, and systemic effects may occur. Lidocaine blocks the generation and conduction of impulses through all nerve fibers-sensory, motor, and autonomic. Lidocaine appears to block conduction of nerve impulses bу decreasing permeability of the nerve cell membrane to sodium ions, thereby decreasing the rate of depolarization of the nerve membrane, increasing threshold for electrical excitability, and preventing propagation of the potential. A current theory is that Lidocaine reduces nerve cell membrane permeability by competing with calcium for the membrane binding sites that control membrane permeability to sodium.

Small nerve fibers are generally more susceptible to the effects of Lidocaine than are large ones. In general, autonomic activity is affected first, followed by loss of pain and other sensory functions, and finally, loss of motor activity; regression of anesthesia usually occurs in the order.

Pharmacokinetics
Lidocaine is readily absorbed from mucous membranes. The rate and extent of absorption depends upon concentration and total dose administered, the specific site of application and duration of exposure. Perfusion rate in the mucous membranes influences on the absorption.

Lidocaine is widely distributed into highly perfused tissues followed by redistribution into skeletal muscle and adipose tissue. Lidocaine is bound to plasma proteins, including α1-acid glycoprotein (AAG). The extent of binding is variable but is about 60-80%. Plasma protein binding of lidocaine depends in part on the concentrations of both lidocaine and AAG. Any alteration in the concentration of AAG can greatly affect plasma concentrations of lidocaine. the elimination half-life is 1 to 2 hours but may be prolonged if infusions are given for longer than 24 hours or if hepatic blood flow is reduced. Lidocaine is largely metabolised in the liver and any alteration in liver function or hepatic blood flow can have a significant effect on its pharmacokinetics and dosage requirements. Metabolism in the liver is rapid and about 90% of a given dose is dealkylated to form monoethylglycinexylidide and glycinexylidide. Both of these metabolites may contribute to the therapeutic and toxic effects of lidocaine and since their half-lives are longer than that of lidocaine, accumulation, particularly of glycinexylidide, may occur during prolonged infusions. Further metabolism occurs and metabolites are excreted in the urine with less than 10% of unchanged lidocaine. Reduced clearance of lidocaine has been found in patients with heart failure, alcoholic liver disease, or chronic or viral hepatitis. Concomitant therapy with drugs that alter hepatic blood flow or induce drug-metabolising microsomal enzymes can also affect the clearance of lidocaine. Renal impairment does not affect the clearance of lidocaine but accumulation of its active metabolites can occur.

Lidocaine crosses the placenta and blood-brain barrier; it is distributed into breast milk.

Uses and Administration
Lidocaine 5% ointment is used for anesthesia of skin and mucous membranes mouth and perianal area.
Dosage of Lidocaine 5% ointment depends on the indications and the area of surface to be anesthetized, tissue vascularity and individual patient tolerance. The lowest dosage necessary to produce adequate anesthesia should be used.

Adults

Pain relief (in anal fissures, haemorrhoids, pruritus ani, pruritus vulvae, herpes zoster, or herpes labialis): 1–2 g applied when necessary; avoid long-term use.

Dental practice: rub gently into dry gum.
Sore nipples from breast-feeding, apply using gauze and wash off immediately before feed.
For endotracheal intubation, apply 1-2 g of ointment before intubation.

Maximum dosage: Lidocaine 5% ointment is used for anesthesia of skin and mucous membranes with a maximum recommended dose of 20 g of 5% ointment (equivalent to 1 g of lidocaine base) in 24 hours.

No more than 2 g (100 mg lidocaine base) in a single dose for endotracheal intubation.
No more than 10 g (500 mg lidocaine base) in a single dose for other indications.
After a maximum endotracheal dose or application to mucous membranes the next dose should not be applied until 4 hours later. After a maximal dose given rectally or to burns the minimum dosing interval should be 8 hours.

Children (Under 12 Years)

It is difficult to recommend a maximum dose of any drug for children since this varies as a function of age and weight. Hence, for safety reasons, in children less than 12 years of age 100% bioavailability should be assumed following application to mucous membranes and broken skin, and the maximum amount of Lidocaine 5% ointmentadministered to children should not be exceed 0.1 g ointment/kg body weight (corresponding to 5 mg lidocaine/kg of body weight). The minimum dosing interval in children should be 8 hours.

For children over 12 years of age doses should be commensurate with weight and physical condition.

Common side effects

Adverse effects apparent after local anesthesia may be the result of blockade of the sympathetic nervous system. For example, after absorption of large amounts through mucous membranes or damaged skin.

CNS and Cardiovascular effects

The systemic toxicity of local anesthetics mainly involves the CNS and the cardiovascular system. Excitation of the CNS may be manifested by restlessness, anxiety, excitement, nervousness, disorientation, confusion, paraesthesias, dizziness, tinnitus, miosis, blurred vision, nausea and vomiting, muscle twitching and tremors. Numbness of the tongue and perioral region, and lightheadedness followed by sedation may appear as early signs of systemic toxicity. Excitation when it occurs may be transient and followed by depression with drowsiness, respiratory failure, and coma.

There may be effects on the cardiovascular system with myocardial depression and peripheral vasodilatation resulting in hypotension and bradycardia; arrhythmias and cardiac arrest may occur.

Allergic reactions are rare (< 0.1%) and may be manifested by cutaneous lesions, urticaria, edema or, in the most severe instances, anaphylactic shock. There appears to be no cross-sensitivity between ester- and amide-type local anesthetics. Idiosyncrasy to local anesthetics has been reported.

Methaemoglobinaemia may occur rarely.

Skin irritation: Topical products that contain propylene glycol may cause skin irritation.

Contraindications
– Traumatized mucosa (increased absorption of anesthetic, leading to increased risk of systemic toxicity).
– Children younger than 2 years of age.
– Known hypersensitivity to lidocaine.
Overdosage

Acute and chronic effects

The systemic toxicity from local anesthetics is generally related to high plasma levels encountered during therapeutic use of local anesthetics and ariginates mainly the CNS and the cardiovascular system.

CNS toxicity: the first symptomsare circumoral paresthesia, numbness of the tongue, dizziness or lightheadedness, hyperacusis and tinnitus, drowsiness, feeling hot, cold, or numb, ringing in ears, shivering or trembling, unusual anxiety, excitement, nervousness, or restlessness, blurred or double vision, confusion, convulsions. Unconsciousness and grand mal convulsions may follow, which may last from a few seconds to several minutes.

Cardiovascular effects may be seen in cases with high systemic concentrations. Severe hypotension, bradycardia, arrythmia, and cardiovascular collaps may be result in such cases.

Acidosis increases the toxic effects of local anesthetics.

Treatment

In the treatment of CNS and cardiovascular reactions, general physiological supportive measures such as maintenance of adequate airway, oxygen uptake, and carbon dioxide removal should be instituted immediately. Administration of oxygen and assisted respiration is necessary.

For reversal of convulsions succinylcholine (50-100 mg) or diazepam (5-15 mg) are required. Also application of barbiturates of short action (sodium thiopental) is possible. In the acute phase of overdosage of lidocaine dialysis is noneffective.

For bradycardia atropine (0.5-1 mg) and sympathomimetics are required intravenously. In case of cardiac arrest immediate closed-chest cardiac massage is necessary.

Precautions

Lidocaine should not be given in dentistry where inflammation or sepsis exists.

Although systemic absorption is low, caution in anaemia, in congenital or acquired methaemoglobinaemia or in G6PD deficiency.

In most cases the patient may participate in application of the anesthetic and should be taught the amount to apply and what systemic side effects are indicators that too much of the drug is being absorbed. These include changes in motor function in the area since that is the last level of local anesthesia. If an allergic reaction occurs, the drug should be immediately discontinued, and symptomatic treatment of itching or rash begun.

Cardiovascular: In general lidocaine should not be given to patients with hypovolemia, heart block or other conduction disturbances, and should be used with caution in patients with congestive heart failure, bradycardia, or respiratory depression.

Neurologic: The risk of central nervous system side effects when using lidocaine in patients with epilepsy is very low, provided that the dose recommendations are followed.

Depending on the dose, local anesthetics may have a very mild effect on mental function and coordination even in the absence of overt CNS toxicity and may temporarily impair locomotion and alertness.

Sensitivity: Lidocaine should be used with caution in persons with known drug sensitivities.Patients allergic to para-aminobenzoic acid derivates (procaine, tetracaine, benzocaine, etc.)have not shown cross sensitivity to lidocaine.

Pregnant Women: Adequate and well-controlled studies in humans have not been done. However, care should be given during early pregnancy when maximum organogenesis takes place.

Nursing Women: No adverse effects have been seen in breast-fed infants whose mothers were receiving lidocaine. Lidocaine is distributed into breast milk in very small quantities that cause no risk to the infant.

Renal: Lidocaine is metabolized primarily by the liver. Only a small fraction of lidocaine is excreted unchanged in the urine. Renal impairment is not expected to significantly affect the pharmacokinetics of lidocaine when LIDOCAINE 5% ointment is used for short treatment durations, according to dosage instructions. Caution is recommended when lidocaine is used in patients with severely impaired renal function because lidocaine metabolites may accumulate during long term treatment.

Hepatic: Because lidocaine is metabolized by the liver , repeated doses should be used cautiously in patients with hepatic disease. Patients with severe hepatic disease, because of their inability to metabolize lidocaine normally, are at greater risk of developing toxic plasma concentrations.

Pediatrics: Children should be given reduced doses commensurate with their age, weight and physical condition because they may be more sensitive to systemic effects due to increased blood levels of lidocaine following repeated doses.The drug should not be used in children younger than 2 years of age, unless prescribed by a physician or dentist.

Geriatrics: systemic toxicity may be more likely to occur in geriatric patients, who may require lower concentrations and/or lower total dosages of mucosal-local anesthetics, especially for endoscopic procedures.

Avoid contact with eyes.

Drug interactions

Antiarrhythmics. There are individual reports of seizures or heart failure and cardiac arrest in patients who received intravenous lidocaine with ajmaline, amiodarone, or tocainide. Delirium has been reported in a patient who received lidocaine with procainamide.

Antiepileptics. Studies in healthy subjects and patients with epilepsy suggest that long-term use of drugs such as phenytoin or barbiturates may increase dosage requirements for lidocaine due to induction of drug-metabolising microsomal enzymes. Phenytoin can also increase plasma concentrations of α1-acid glycoprotein and thereby reduce the free fraction of lidocaine in plasma.

The cardiac depressant effects of lidocaine may be dangerously enhanced by intravenous phenytoin.

Beta blockers. Significant increases in plasma-lidocaine concentrations have occurred with propranolol, owing to a reduction in the clearance of lidocaine from plasma. A similar interaction has occurred with nadolol.

H2-antagonists. Cimetidine may inhibit hepatic metabolism of lidocaine, leading to increased risk of lidocaine toxicity, especially if lidocaine is applied to the mucosa in large quantities, used repeatedly, used in the oral or pharyngeal area.

Hypokalaemia produced by acetazolamide, loop diuretics, and thiazides antagonizes the effect of lidocaine.

Adverse effects may also be caused by vasoconstrictors given with the anesthetic.

Presentation

15 g of ointment is filled into aluminum tubes (inside package).
The tubes are packed and inserted with the leaflet into cardboard boxes (outer package).

Expiry date

3 years. Do not use after the expiration date.

Prescription status

To be dispensed without prescription.

Storage conditions

Store at a room temperature, in a dry place, out of the reach of children. Protect from light.