Lidoderm

Lidoderm is a prescription medication used to relieve pain associated with post-herpetic neuralgia. Painful symptoms of post-herpetic neuralgia may include burning, stabbing pain, and aches.

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

Any medications applied to the skin or taken by mouth to treat pain

• disopyramide (Norpace)
• flecainide (Tambocor)
• mexiletine (Mexitil)
• moricizine (Ethmozine)
• procainamide (Procanabid, Pronestyl)
• propafenone (Rhythmol)
• quinidine (Quinidex)
• tocainide (Tonocard)

This is not a complete list of Lidoderm drug interactions. Ask your doctor or pharmacist for more information.

Take Lidoderm exactly as prescribed.

This medication comes in a patch that is applied to the skin. Up to 3 patches may be applied at once and the patches may be left in place for up to 12 hours per day.

To apply the patches, follow these steps:

• Look at the skin that you plan to cover with a Lidoderm patch. If the skin is broken or blistered, do not apply a patch to that area.
• Use scissors to remove the outer seal from the package. Pull apart the zipper seal.
• Remove the appropriate number of patches from the package and press the zipper seal tightly together. The remaining patches may dry out if the zipper seal is not tightly closed.
• Cut patch(es) to the size and shape that will cover your most painful area.
• Peel the transparent liner off the back of the patch(es).
• Press the patch(es) firmly onto your skin. If you are applying a patch to your face, be careful not to let it touch your eyes. If you do get Lidoderm in your eye, wash it with plenty of water or saline solution.
• Wash your hands after handling Lidoderm.

Do not reuse Lidoderm. After you are finished using a patch, remove it and dispose of it out of reach of children and pets. Used patches contain enough medication to seriously harm a child or pet.

Avoid contact with water, such as bathing, swimming or showering.

Lidoderm is usually used as needed. If your doctor has told you to use Lidoderm patches regularly, use the missed patch as soon as you remember it. However, if it is almost time for the next dose, skip the missed patch and continue your regular dosing schedule. Do not use a double dose to make up for a missed one.

Use Lidoderm as ordered by your doctor. Read all information given to you. Follow all instructions closely.

• Put on the most painful parts of the skin.
• Trim patch to cover the affected skin.
• Put patch on at the same time of day.
• Leave on for up to 12 hours.
• After you take the patch off, do not put another patch on that area of skin for 12 hours.
• Take off the patch right away if it burns.
• After you take off a skin patch, be sure to fold the sticky sides of the patch to each other.

What do I do if I miss a dose?

• If you use this medicine on a regular basis, put on a missed dose as soon as you think about it.
• If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
• Do not put on 2 doses at the same time or extra doses.
• Many times Lidoderm is used on an as needed basis. Do not use more often than told by the doctor.

• Store at room temperature. Do not freeze.
• Protect from heat.
• Store in the pouch that comes with this medicine to help keep away from children.
• Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
• Check with your pharmacist about how to throw out unused drugs.

Pharmacodynamics

Lidocaine is an amide-type local anesthetic agent and is suggested to stabilize neuronal membranes by inhibiting the ionic fluxes required for the initiation and conduction of impulses.

The penetration of lidocaine into intact skin after application of Lidoderm is sufficient to produce an analgesic effect, but less than the amount necessary to produce a complete sensory block.

Pharmacokinetics

Absorption
The amount of lidocaine systemically absorbed from Lidoderm is directly related to both the duration of application and the surface area over which it is applied. In a pharmacokinetic study, three Lidoderm patches were applied over an area of 420 cm2 of intact skin on the back of normal volunteers for 12 hours. Blood samples were withdrawn for determination of lidocaine concentration during the application and for 12 hours after removal of patches. The results are summarized in Table 1.

When Lidoderm is used according to the recommended dosing instructions, only 3 ± 2% of the dose applied is expected to be absorbed. At least 95% (665 mg) of lidocaine will remain in a used patch. Mean peak blood concentration of lidocaine is about 0.13 µg/mL (about 1/10 of the therapeutic concentration required to treat cardiac arrhythmias). Repeated application of three patches simultaneously for 12 hours (recommended maximum daily dose), once per day for three days, indicated that the lidocaine concentration does not increase with daily use. The mean plasma pharmacokinetic profile for the 15 healthy volunteers is shown in Figure 1.

Figure 1
Mean lidocaine blood concentrations after three consecutive daily applications of three Lidoderm patches simultaneously for 12 hours per day in healthy volunteers (n = 15).

Distribution
When lidocaine is administered intravenously to healthy volunteers, the volume of distribution is 0.7 to 2.7 L/kg (mean 1.5 ± 0.6 SD, n = 15). At concentrations produced by application of Lidoderm, lidocaine is approximately 70% bound to plasma proteins, primarily alpha-1-acid glycoprotein. At much higher plasma concentrations (1 to 4 µg/mL of free base), the plasma protein binding of lidocaine is concentration dependent. Lidocaine crosses the placental and blood brain barriers, presumably by passive diffusion.

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. A minor metabolite, 2,6-xylidine, has unknown pharmacologic activity but is carcinogenic in rats. The blood concentration of this metabolite is negligible following application of Lidoderm (lidocaine patch 5%). Following intravenous administration, MEGX and GX concentrations in serum range from 11 to 36% and from 5 to 11% of lidocaine concentrations, respectively.

Excretion
Lidocaine and its metabolites are excreted by the kidneys. Less than 10% of lidocaine is excreted unchanged. The half-life of lidocaine elimination from the plasma following IV administration is 81 to 149 minutes (mean 107 ± 22 SD, n = 15). The systemic clearance is 0.33 to 0.90 L/min (mean 0.64 ± 0.18 SD, n = 15).

Single-dose treatment with Lidoderm was compared to treatment with vehicle patch (without lidocaine), and to no treatment (observation only) in a double-blind, crossover clinical trial with 35 post-herpetic neuralgia patients. Pain intensity and pain relief scores were evaluated periodically for 12 hours. Lidoderm performed statistically better than vehicle patch in terms of pain intensity from 4 to 12 hours.

Multiple-dose, two-week treatment with Lidoderm was compared to vehicle patch (without lidocaine) in a double-blind, crossover clinical trial of withdrawal-type design conducted in 32 patients, who were considered as responders to the open-label use of Lidoderm prior to the study. The constant type of pain was evaluated but not the pain induced by sensory stimuli (dysesthesia). Statistically significant differences favoring Lidoderm were observed in terms of time to exit from the trial (14 versus 3.8 days at p-value <0.001), daily average pain relief, and patient's preference of treatment. About half of the patients also took oral medication commonly used in the treatment of post-herpetic neuralgia. The extent of use of concomitant medication was similar in the two treatment groups.

Lidoderm is contraindicated in patients with a known history of sensitivity to local anesthetics of the amide type, or to any other component of the product.

Application Site Reactions

During or immediately after treatment with Lidoderm (lidocaine patch 5%), the skin at the site of application may develop blisters, bruising, burning sensation, depigmentation, dermatitis, discoloration, edema, erythema, exfoliation, irritation, papules, petechia, pruritus, vesicles, or may be the locus of abnormal sensation. These reactions are generally mild and transient, resolving spontaneously within a few minutes to hours.

Allergic Reactions

Allergic and anaphylactoid reactions associated with lidocaine, although rare, can occur. They are characterized by angioedema, bronchospasm, dermatitis, dyspnea, hypersensitivity, laryngospasm, pruritus, shock, and urticaria. If they occur, they should be managed by conventional means. The detection of sensitivity by skin testing is of doubtful value.

Other Adverse Events

Due to the nature and limitation of spontaneous reports in postmarketing surveillance, causality has not been established for additional reported adverse events including:

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, and tremor.

Systemic (Dose-Related) Reactions

Systemic adverse reactions following appropriate use of Lidoderm are unlikely, due to the small dose absorbed (see CLINICAL PHARMACOLOGY, Pharmacokinetics). Systemic adverse effects of lidocaine are similar in nature to those observed with other amide local anesthetic agents, including CNS excitation and/or depression (light headedness, nervousness, apprehension, euphoria, confusion, dizziness, drowsiness, tinnitus, blurred or double vision, vomiting, sensations of heat, cold or numbness, twitching, tremors, convulsions, unconsciousness, respiratory depression and arrest). Excitatory CNS reactions may be brief or not occur at all, in which case the first manifestation may be drowsiness merging into unconsciousness. Cardiovascular manifestations may include bradycardia, hypotension and cardiovascular collapse leading to arrest.

Apply Lidoderm to intact skin to cover the most painful area. Apply the prescribed number of patches (maximum of 3), only once for up to 12 hours within a 24 hour period. Patches may be cut into smaller sizes with scissors prior to removal of the release liner. (See HANDLING AND DISPOSAL) Clothing may be worn over the area of application. Smaller areas of treatment are recommended in a debilitated patient, or a patient with impaired elimination.

If irritation or a burning sensation occurs during application, remove the patch(es) and do not reapply until the irritation subsides.

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

Lidoderm may not stick if it gets wet. Avoid contact with water, such as bathing, swimming or showering.     

Use this medicine exactly as directed on the label, or as it has been prescribed by your doctor. Do not apply this medicine in larger amounts than recommended.

Improper use of lidocaine topical may result in death.

Lidocaine topical comes in many different forms (gel, spray, cream, lotion, ointment, liquid, skin patch).

Do not take by mouth. Lidocaine topical is for use only on the skin. If this medicine gets in your eyes, nose, mouth, rectum, or vagina, rinse with water.

Use the smallest amount of medicine needed to numb the skin or relieve pain. Your body may absorb too much of this medicine if you use too much, if you apply it over large skin areas, or if you apply heat, bandages, or plastic wrap to treated skin areas. Skin that is cut or irritated may also absorb more topical medication than healthy skin.

Do not apply this medicine to swollen skin areas or deep puncture wounds. Avoid using the medicine on skin that is raw or blistered, such as a severe burn or abrasion.

Do not cover treated skin unless your doctor has told you to.

Lidocaine topical may be applied with your finger tips or a cotton swab.

If your medicine comes with patient instructions for safe and effective use, follow these directions carefully. Ask your doctor or pharmacist if you have any questions.

Store at room temperature away from moisture and heat.

Keep both used and unused lidocaine topical skin patches out of the reach of children or pets. The amount of lidocaine in the skin patches could be harmful to a child or pet who accidentally sucks on or swallows the patch. Seek emergency medical attention if this happens.

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

• severe burning, stinging, or irritation where the medicine was applied;

• swelling or redness;

• sudden dizziness or drowsiness after medicine is applied;

• confusion, blurred vision, ringing in your ears; or

• unusual sensations of temperature.

Common side effects include:

• mild irritation where the medication is applied; or

• numbness in places where the medicine is accidentally applied.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.