A lidocaine patch is a medication delivery system applied directly to the skin to provide localized pain relief. The patch contains the drug lidocaine, which belongs to a class of medicines known as local anesthetics. It is designed to allow the anesthetic to slowly soak into the skin and target the nerve endings underneath. This topical approach allows the medication to work directly at the site of discomfort, reducing pain signals before they can travel to the brain.
The Science of Pain Relief: How Lidocaine Blocks Nerve Signals
The sensation of pain starts with an electrical impulse generated by nerve cells in the affected area. This electrical signal, known as an action potential, is created when charged sodium ions rush into the nerve cell through tiny openings in the cell membrane. These microscopic openings are called voltage-gated sodium channels, and their opening allows the pain message to begin its journey.
Lidocaine functions as a molecular roadblock that prevents the transmission of this signal. As the drug permeates the skin, it binds to the interior of these voltage-gated sodium channels. This binding effectively stabilizes the channel in a closed state, blocking the influx of sodium ions into the nerve cell.
By inhibiting this sodium movement, lidocaine temporarily increases the nerve cell’s threshold for electrical excitability. The nerve is unable to depolarize sufficiently to generate or propagate the electrical impulse toward the spinal cord and brain. This mechanism means the pain message is stopped locally at the nerve endings in the skin, resulting in a loss of pain sensation in the targeted area without causing widespread numbness.
Localized Pain Conditions Treated by Patches
The patch delivery system is especially suited for managing pain that is close to the skin surface, providing targeted relief with minimal absorption into the bloodstream. The most common condition treated by prescription-strength lidocaine patches is Post-Herpetic Neuralgia (PHN). This is a chronic, often severe, type of nerve pain that can persist after a shingles infection has resolved.
Lidocaine patches are also frequently used for other superficial localized neuropathic pain syndromes, such as diabetic peripheral neuropathy. The targeted action of the patch is effective because it treats damaged nerve endings that are sending erroneous pain signals.
While primarily used for nerve pain, the patches can also help alleviate localized musculoskeletal pain conditions like lower back pain, carpal tunnel syndrome, and osteoarthritis joint pain. For these conditions, the patch provides analgesia to the tissue near the skin without producing a complete sensory block of the deeper structures.
Proper Application and Safety Guidelines
Correct application of the lidocaine patch is necessary to ensure maximum effectiveness and safety. The area of skin where the patch will be placed must be clean, dry, and completely intact. It should not be applied over irritated, cut, or broken skin. Many patches can be cut into smaller sizes before application to fit the specific contours of the painful area, but they should not be overlapped.
The standard recommendation for prescription patches is to apply them for a maximum of 12 hours within any 24-hour period, followed by a 12-hour patch-free interval. This wearing schedule helps prevent skin irritation and reduces the risk of excessive systemic absorption of the drug. Hands should always be washed thoroughly after applying or removing a patch to prevent accidental transfer of the medication.
Safety Precautions
Avoid placing external heat sources, such as heating pads or electric blankets, over the patch. Heat can increase the rate at which lidocaine is absorbed into the body, raising the risk of systemic side effects. Used patches should be folded in half so the adhesive sides stick to each other. They must then be immediately disposed of in a location inaccessible to children or pets, as they still contain residual medication.