WARNINGS
Included as part of the PRECAUTIONS section.
PRECAUTIONS
General
EXCESSIVE DOSAGE, OR SHORT INTERVALS BETWEEN DOSES, CAN RESULT IN HIGH PLASMA
LEVELS OF LIDOCAINE OR ITS METABOLITES AND SERIOUS ADVERSE EFFECTS. Following
too high or repeated doses of viscous lidocaine in children under the age of
three, serious side effects have been reported. Absorption from the wound surfaces
and mucous membranes is variable but is especially high from the bronchial tree.
Such applications may therefore result in rapidly rising or excessive plasma
concentrations, with an increased risk for toxic symptoms, such as convulsions.
PATIENTS SHOULD BE INSTRUCTED TO STRICTLY ADHERE TO THE RECOMMENDED DOSAGE.
This is especially important in children where doses vary with weight. The management
of serious adverse reactions may require the use of resuscitative equipment,
oxygen and other resuscitative drugs (see OVERDOSAGE).
The lowest dosage that results in effective anesthesia should be used to avoid
high plasma levels and serious adverse effects. Tolerance to elevated blood
levels varies with the status of the patient.
XYLOCAINE VISCOUS 2% (lidocaine hydrochloride) IS FOR TOPICAL USE ONLY AND
MUST NOT BE USED FOR INJECTION.
Lidocaine should be used with caution in patients with sepsis and/or traumatized
mucosa at the area of application, since under such conditions there is the
potential for rapid systemic absorption.
XYLOCAINE Viscous (lidocaine hydrochloride solution) 2% should be used with caution in children under the age
of 2 as there is insufficient data to support the safety and efficacy of this
product in this patient population at this time.
In patients under general anesthesia who are paralyzed, higher plasma concentrations
may occur than in spontaneously breathing patients. Unparalyzed patients are
more likely to swallow a large proportion of the dose, which then undergoes
considerable first-pass hepatic metabolism following absorption from the gut.
Avoid contact with eyes.
Many drugs used during the conduct of anesthesia are considered potential triggering
agents for familial malignant hyperthermia. It has been shown that the use of
amide local anesthetics in malignant hyperthermia patients is safe. However
there is no guarantee that neural blockade will prevent the development of malignant
hyperthermia during surgery. It is also difficult to predict the need for supplemental
general anesthesia. Therefore a standard protocol for the management of malignant
hyperthermia should be available.
When topical anesthetics are used in the mouth, the patient should be aware
that the production of topical anesthesia may impair swallowing and thus enhance
the danger of aspiration. Numbness of the tongue or buccal mucosa may enhance
the danger of unintentional biting trauma. Food or chewing gum should not be
taken while the mouth or throat area is anesthetized. See also Part III: Consumer
Information.
XYLOCAINE Viscous (lidocaine hydrochloride solution) 2% is ineffective when applied to intact skin.
Lidocaine has been shown to be porphyrinogenic in animal models. XYLOCAINE
Topical 4% should only be prescribed to patients with acute porphyria on strong
or urgent indications, when they can be closely monitored. Appropriate precautions
should be taken for all porphyric patients.
Cardiovascular
Lidocaine should be used with caution in patients with bradycardia or impaired
cardiovascular function since they may be less able to compensate for functional
changes associated with the prolongation of A-V conduction produced by amide-type
local anesthetics. Lidocaine should be used with caution in patients in severe
shock.
Neurologic
Epilepsy: 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 (See DOSAGE AND ADMINISTRATION).
Locomotion and Coordination: Topical lidocaine formulations generally
result in low plasma concentrations because of a low degree of systemic absorption.
However, 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.
Renal
Lidocaine is metabolized primarily by the liver to monoethylglycinexylidine
(MEGX, which has some CNS activity), and then further to metabolites glycinexylidine
(GX) and 2,6-dimethylaniline (see ACTION AND CLINICAL
PHARMACOLOGY). Only a small fraction (2%) of lidocaine is excreted unchanged
in the urine. The pharmacokinetics of lidocaine and its main metabolite were
not altered significantly in haemodialysis patients (n=4) who received an intravenous
dose of lidocaine. Therefore, renal impairment is not expected to significantly
affect the pharmacokinetics of lidocaine when XYLOCAINE Viscous (lidocaine hydrochloride solution) 2% is used for
short treatment durations, according to dosage instructions (see DOSAGE
AND ADMINISTRATION). Caution is recommended when lidocaine is used in
patients with severely impaired renal function because lidocaine metabolites
may accumulate during long term treatment (see DOSAGE
AND ADMINISTRATION). Hepatic
Because amide-type local anesthetics such as lidocaine are metabolized by the
liver, these drugs, especially repeated doses, should be used cautiously in
patients with hepatic disease. Patients with severe hepatic disease, because
of their inability to metabolize local anesthetics normally, are at greater
risk of developing toxic plasma concentrations.
Sensitivity
Lidocaine should be used with caution in persons with known drug sensitivities.
XYLOCAINE Viscous (lidocaine hydrochloride solution) 2% is contraindicated in patients with known hypersensitivities
to local anesthetics of the amide type, to other components in the formulation,
methylparaben and/or propylparaben (preservatives) and their metabolite para
amino benzoic acid (PABA). The use of paraben-containing lidocaine preparations
should also be avoided in patients who are allergic to ester local anesthetics
(see CONTRAINDICATIONS).
Special Populations
Debilitated patients, acutely ill patients and patients with sepsis 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.
Pregnant Women: There are no adequate and well-controlled studies in
pregnant women on the effect of lidocaine on the developing fetus.
It is reasonable to assume that a large number of pregnant women and women
of child-bearing age have been given lidocaine. No specific disturbances to
the reproductive process have so far been reported, e.g. no increased incidence
of malformations. However, care should be given during early pregnancy when
maximum organogenesis takes place.
Labour and Delivery: Should XYLOCAINE Viscous (lidocaine hydrochloride solution) 2% be used concomitantly
with other products containing lidocaine during labour and delivery, the total
dose contributed by all formulations must be kept in mind.
Nursing Women: Lidocaine and its metabolites are excreted in the breast
milk. At therapeutic doses the quantities of lidocaine and its metabolites in
breast milk are small and generally are not expected to be a risk for the infant.
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 (see DOSAGE AND ADMINISTRATION).
XYLOCAINE Viscous (lidocaine hydrochloride solution) 2% should be used with caution in children under the age
of 2 as there is insufficient data to support the safety and efficacy of this
product in this patient population at this time.
Geriatrics: Elderly patients may be more sensitive to systemic effects
due to increased blood levels of lidocaine following repeated doses and may
require dose reductions.
Carcinogenesis and Mutagenesis
Genotoxicity tests with lidocaine showed no evidence of mutagenic potential.
A metabolite of lidocaine, 2,6-dimethylaniline, showed weak evidence of activity
in some genotoxicity tests. A chronic oral toxicity study of the metabolite
2,6-dimethylaniline (0, 14, 45, 135 mg/kg) administered in feed to rats showed
that there was a significantly greater incidence of nasal cavity tumors in male
and female animals that had daily oral exposure to the highest dose of 2,6-dimethylaniline
for 2 years. The lowest tumor-inducing dose tested in animals (135 mg/kg) corresponds
to approximately 50 times the amount of 2,6-dimethylaniline to which a 50 kg
subject would be exposed following the application of 20 g of lidocaine viscous
2% for 24 hours on the mucosa, assuming the highest theoretical extent of absorption
of 100% and 80% conversion to 2,6-dimethylaniline. Based on a yearly exposure
(once daily dosing with 2,6-dimethylaniline in animals and 5 treatment sessions
with 20 g lidocaine viscous 2% in humans), the safety margins would be approximately
3400 times when comparing the exposure in animals to man.