lidocaine transdermal (Rx, OTC)

Frequency Not Defined

Allergic and anaphylactoid reactions (rare) may be characterized by angioedema, bronchospasm, dermatitis, dyspnea, hypersensitivity, laryngospasm, pruritus, shock, and urticaria

Application site reactions may occur (eg, blisters, bruising, burning sensation, depigmentation, dermatitis, discoloration, edema, erythema, exfoliation, irritation, papules, petechia, pruritus, vesicles, or abnormal sensation

Postmarketing Reports

Asthenia, confusion, disorientation, dizziness, headache, hyperesthesia, hypoesthesia, lightheadedness, metallic taste, nausea, nervousness, pain exacerbated, paresthesia, somnolence, taste alteration, vomiting, visual disturbances such as blurred vision, flushing, tinnitus, eye irritation, and tremor

Contraindications

Known history of sensitivity to local anesthetics of the amide type, or to any other component of the product

Cautions

Patients allergic to para-aminobenzoic acid (PABA) derivatives (eg, procaine, tetracaine, benzocaine) have not shown cross-sensitivity to lidocaine; however, be aware of the potential for cross-sensitivity in patients allergic to PABA derivatives, especially if the etiologic agent is uncertain

If irritation or a burning sensation occurs during application, advise patients to remove patch and do not reapply until the irritation subsides

When used concomitantly with other products containing local anesthetic agents, the amount of lidocaine absorbed from all formulations must be considered

Dispose of used lidocaine patches properly to avoid toxicity in small children or pets; used lidocaine patches contains a large amount of lidocaine

Application to broken or inflamed skin, although not tested, may result in higher blood concentrations of lidocaine from increased absorption; apply only to intact skin

External heat sources (eg, heating pads, electric blanket), longer duration of application, application of more than recommended number of patches, smaller patients, impaired elimination may contribute to increase systemic absorption from transdermal patch; advice patients of proper application and duration

Severe hepatic impairment may decrease systemic elimination of lidocaine

If eye contact occurs, immediately wash out eye with water or saline and protect the eye until sensation returns

Pregnancy

There are no available data regarding use in pregnant women

Reproduction studies with lidocaine have been performed in rats at doses up to 30 mg/kg SC and have revealed no evidence of harm to the fetus due to lidocaine

There are, however, no adequate and well-controlled studies in pregnant women

Because animal reproduction studies are not always predictive of human response, should be used during pregnancy only if clearly needed

Lactation

There are no available data regarding use in breastfeeding women; caution if administered

Lidocaine is excreted in human milk, and the milk: plasma ratio of lidocaine is 0.4

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Elicits local anesthesia; stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses, thereby effecting local anesthetic action

Absorption

Peak plasma time (transdermal patch): 11 hr

Peak plasma concentration (3 transdermal patches): 0.13 mcg/mL

Distribution

Protein bound: 70% (transdermal patch)

Vd: 0.7-2.7 L/kg (transdermal patch)

Metabolism

It is not known if lidocaine is metabolized in the skin

Lidocaine is metabolized rapidly by the liver to a number of metabolites, including monoethylglycinexylidide (MEGX) and glycinexylidide (GX), both of which have pharmacologic activity similar to, but less potent than that of lidocaine

Transdermal Administration

Instruct patients to wash hands immediately after handling patch and to avoid contact with eyes

Patch may not stick if it gets wet; advise patients to avoid contact with water (eg, bathing, swimming, or showering) during the 12 hr when the patch is worn

Advise patients not to apply external heat sources (eg, heating pads or electric blankets) directly to lidocaine transdermal patches because plasma lidocaine levels are increased

The patch can be applied, however, to the administration site after moderate heat exposure (eg, 15 minutes of heating pad exposure on a medium setting)

May be used during moderate exercise (eg, biking for 30 minutes)

Topical systems that have lifted at the edges may be reattached by pressing firmly on the edges; if a patch comes off completely and will not stick to patient’s skin, it should be thrown away and a new patch should be applied for a total duration of 12 hr of used and new patched together

Dispose of properly

• Instruct patients to, after use, fold used patch so that the adhesive side sticks to itself and safely discard the used patch or pieces of cut patch where children and pets cannot get to them

Storage

Store at 25°C (77°F); excursions permitted to 15-30°C (59-86°F)

Store inside original sealed package and to apply immediately after removal from the package

Store out of the reach of children, pets, and others