ACTION AND MECHANISM

- A local anesthetic of the amide type. Lidocaine blocks voltage-gated Na+ channels, decreasing the rate of neuronal depolarization and the conduction velocity of the nerve impulse. The blockade is reversible, and once the concentration falls below a minimum threshold, the nerve fully recovers its function.
The blocking effect is not accompanied by alterations in the resting potential or repolarization.
The anesthetic effects appear rapidly, in about 3-5 minutes, and last for about 1.5 hours.

SPECIAL WARNINGS

- The minimum doses that eliminate symptoms should always be used to avoid the risk of systemic effects.
- Monitoring:
* Cardiac function, including ECG monitoring, in people with severe cardiovascular disease.

SENIORS

No specific problems have been described in the elderly that would require a dosage adjustment.

PATIENT ADVICE

- Use the dose recommended by your doctor.
Do not apply lidocaine to mucous membranes, including the eyes, or to irritated, inflamed, or broken skin. In case of contact with the eyes, immediately rinse them with lukewarm water or saline solution and protect them until sensitivity returns.
- Before starting treatment, you should inform your doctor if you have previously suffered or are currently suffering from:
* Severe liver diseases.
* Serious heart conditions, including cardiac arrhythmias.
- Inform your doctor if you are being treated with:
* Antiarrhythmic medications.
* Medications for myocardial infarction, such as nitroglycerin.
* Nitrofurantoin, an antibiotic for urinary tract infections.
* Nitroprusside, a medication for high blood pressure.
- Inform your doctor and/or pharmacist if you experience any of these symptoms:
* Allergy symptoms, such as skin rashes, hives, chest tightness, difficulty or noises when breathing, or dizziness.

CONTRAINDICATIONS

- Hypersensitivity to lidocaine or [ALLERGY TO AMIDE-TYPE LOCAL ANESTHETICS], between which cross-hypersensitivity reactions may exist.

EFFECTS ON DRIVING

No special risks to driving ability are estimated.

PREGNANCY

FDA Category B.
Animal safety: Lidocaine did not exhibit teratogenic effects in rats or rabbits. At maternally toxic doses in rabbits, an increase in fetal mortality has been observed. In rats, a reduction in postnatal survival has been reported.
Safety in humans: Lidocaine crosses the placenta. There are no adequate and well-controlled studies in humans. In general, occasional use during pregnancy may be acceptable, provided the lowest possible dose is used for the shortest possible duration.
Effects on fertility: No adverse effects have been reported in male or female rats. No studies have been conducted in humans.

PHARMACOKINETICS

- Absorption: Systemic bioavailability depends on the amount of lidocaine applied, the application time, and the condition of the skin. Therefore, absorption through intact skin is very low, but it may increase when applied to mucous membranes or damaged skin.
- Distribution: moderate binding to plasma proteins (65%), primarily to alpha-1 acid glycoprotein. The Vd is 1.5 L/kg. Like other local anesthetics, it is able to cross the blood-brain barrier and placenta.
- Metabolism: Extensive hepatic metabolism (90-95%) via N-dealkylation reactions, yielding monoethylglycinexylide and glycinexylide. Both are hydrolyzed to 2,6-xylidine, which is hydroxylated to 4-hydroxy-2,6-xylidine. All metabolites are less active than lidocaine. Metabolism is primarily mediated by CYP1A2, and to a lesser extent by CYP3A4.
- Excretion: primarily in urine (90%), with 5-10% unchanged and 80% as 4-hydroxy-2,6-xylidine. The t1/2 after IV administration is 1.5-2 h, while after topical application it can reach 12 h, indicating deposition in the skin and slow release into the bloodstream. The Clt is 8-10 ml/min/kg.
Pharmacokinetics in special situations:
- Renal insufficiency: the t1/2 may increase to 2-3 h, resulting in accumulation of active metabolites. Lidocaine is removed by hemodialysis.
- Liver failure: an accumulation of lidocaine may occur, as metabolism may decrease to up to 10% of the metabolism observed in patients with normal liver function.

INDICATIONS

- [VAGINAL ITCHING]. Symptomatic and temporary relief of itching in the external vaginal area, such as that caused by underwear, soap or deodorants.

INTERACTIONS

No specific studies have been conducted on interactions with topical lidocaine. It should be noted that in the event of significant systemic absorption, the usual interactions with parenterally administered lidocaine may occur.
- Class I and III antiarrhythmics. Risk of increased toxicity.
- Drugs such as nitrates, nitrofurantoin, nitroglycerin, nitroprusside, or quinine may increase the risk of methemoglobinemia.

LACTATION

Lidocaine is excreted in breast milk, but due to its low absorption, it is unlikely to affect the infant. Its use is acceptable.
The American Academy of Pediatrics and the WHO consider it compatible with breastfeeding.

CHILDREN

Safety and efficacy have not been evaluated in girls under 12 years of age, so its use is not recommended.

GUIDELINES FOR PROPER ADMINISTRATION

- Vaginal cream: Apply the vaginal cream to the affected area with a gentle massage. Wash your hands afterwards.

POSOLOGY

It is recommended to use the minimum dose that eliminates symptoms to avoid possible systemic effects.

DOSAGE IN HEPATIC INSUFFICIENCY

- Mild to moderate hepatic impairment (Child-Pugh classes A and B): no dosage adjustment required.
- Severe hepatic impairment (Child-Pugh class C): caution.

DOSAGE IN RENAL INSUFFICIENCY

- Mild to moderate renal insufficiency (CLcr 30-90 ml/min): no dosage adjustment required.
- Severe renal impairment (CLcr < 30 ml/min): caution.

PRECAUTIONS

- Severe [RENAL INSUFFICIENCY] (CLcr < 30 ml/min). Safety and efficacy have not been evaluated.
- [HEPATIC INSUFFICIENCY]. Risk of accumulation due to its high hepatic metabolism. Caution in patients with severe hepatic impairment (Child-Pugh class C).
- Cardiotoxicity. Lidocaine has effects on cardiac conduction and contractility. The efficacy and safety of topical lidocaine have not been evaluated in patients with severe cardiovascular diseases such as heart failure, cardiac arrhythmia, hypovolemic shock, or cardiogenic shock. Close monitoring of these patients is recommended due to the risk of worsening of their condition, along with monitoring of cardiac function and ECG. Prolonged use should be avoided.
- Avoid using this product on mucous membranes, including the eyes, as well as on irritated, inflamed, or broken skin, as this could increase systemic absorption. In case of contact with the eyes, immediately rinse them with lukewarm water or saline solution and protect them until sensitivity returns, as there is a risk of corneal abrasion and irritation.
- [METHEMOGLOBINEMIA]. Lidocaine may worsen the symptoms.

PRECAUTIONS RELATING TO EXCIPIENTS

- Because it contains castor oil, it may cause allergic skin reactions.

ADVERSE REACTIONS

Adverse reactions are described according to each frequency interval, being considered very common (>10%), common (1-10%), uncommon (0.1-1%), rare (0.01-0.1%), very rare (<0.01%) or of unknown frequency (cannot be estimated from the available data).
- Dermatological: Infrequent local adverse reactions, such as redness or paleness, skin irritation, itching, or a burning sensation. These reactions are usually due to the anesthetic effect on blood vessels and are generally mild and transient.
- Allergic: rare [CONTACT DERMATITIS]; very rare [HYPERSENSITIVITY REACTIONS], which usually present with [URTICARIA], [EDEMA], [BRONCHIAL SPASM], and which in severe cases could lead to [ANAPHYLAXIS].
However, in the event of significant systemic absorption, systemic symptoms may occur (see Lidocaine, N01BB).

OVERDOSE

Symptoms: Due to its route of administration, poisoning is unlikely. However, severe poisoning has been reported in young children who received very high topical doses (8.6-17.2 mg/kg).
As with any other local anesthetic, overdose can lead to a neurological syndrome characterized by initial excitation (although this phase may not occur) with nervousness, euphoria, confusion, and seizures, followed by depression with drowsiness, loss of consciousness, respiratory depression, and coma. Additional symptoms may include nausea, tremors, tinnitus, blurred vision, as well as cardiovascular symptoms such as hypotension, cardiac depression, and vascular collapse.
Treatment:
- Antidote: there is no specific antidote.
- General elimination measures: lidocaine is hemodialyzable.
- Monitoring: closely monitor the patient, ensuring their respiratory and cardiovascular function, with ECG and blood pressure monitoring.
- Medication:
* Seizures: IV diazepam (0.1 mg/kg) or succinylcholine (10-50 mg).
* Respiratory depression: administration of oxygen.
* Hypotension: vasoconstrictors (preferably with myocardial stimulating activity), administration of parenteral fluids and even blood transfusion.
* Methemoglobinemia: 1% methylene blue, IV, at a dose of 1-2 mg/kg for 10 min.

COMPOSITION

LIDOCAINE (TOPICO): 20 MILLIGRAMS
CASTOR OIL (EXCIPIENT): 0