Lidocaine patches are a topical analgesic that delivers the local anesthetic lidocaine directly through the skin to nerves in a specific area. This method provides localized relief with minimal systemic exposure compared to oral medications. The patch adheres to the skin, allowing the medication to slowly diffuse into underlying tissues to interrupt pain signals. Although the primary effect is local numbness, medicine applied to the skin can be absorbed into the bloodstream, raising questions about potential systemic side effects.
Is Nausea a Known Side Effect?
Yes, nausea and related gastrointestinal discomfort are recognized, though generally uncommon, side effects associated with lidocaine patches. When used correctly, the amount of lidocaine absorbed into the bloodstream is usually small, keeping the risk of systemic reactions low. However, if the medication is absorbed more quickly than intended, it can cause systemic effects by influencing the central nervous system.
These systemic effects, such as nausea, vomiting, dizziness, or lightheadedness, signal that the medication has circulated throughout the body. This is distinct from common localized side effects, which include mild redness, itching, or irritation of the skin at the application site. Although infrequent, nausea is listed among the possible adverse events reported.
Nausea or vomiting suggests that the concentration of lidocaine in the bloodstream is higher than needed for localized pain relief. Other signs of systemic exposure include changes in taste, such as a metallic flavor, or central nervous system effects like nervousness or confusion. These symptoms are dose-related, becoming more likely as the amount of absorbed drug increases. Using the patch as directed minimizes the likelihood of these systemic issues.
Understanding Systemic Absorption
The mechanism by which a topical patch causes a whole-body reaction like nausea is systemic absorption. Lidocaine must pass through the skin barrier via transdermal delivery to reach underlying tissues. While the skin naturally resists passage, the drug is designed to penetrate into the bloodstream. Under normal use, the amount absorbed is small and regulated.
Several factors increase the rate and amount of lidocaine entering the circulation, raising the risk of systemic side effects. A primary factor is the duration and extent of application; using more patches or wearing them longer than the recommended 12 hours leads to higher blood concentrations. The total surface area covered directly correlates with the total drug dose delivered.
The integrity of the skin at the application site is another major factor. Applying the patch to broken, irritated, or inflamed skin bypasses the natural barrier function of the epidermis. This compromised skin allows for faster and more extensive absorption, leading to unexpectedly high systemic levels. Manufacturers warn against applying the patch to damaged skin.
The application of external heat sources is a significant concern, as heat dramatically increases blood flow and permeability. Applying a heating pad or electric blanket over or near the patch site can increase the absorption rate of lidocaine significantly. This surge can quickly push the drug concentration into a range that produces systemic symptoms like nausea and dizziness. Avoiding external heat is a safety measure to maintain controlled drug delivery.
Steps for Managing Gastrointestinal Discomfort
If you feel symptoms like nausea, vomiting, or lightheadedness while wearing a lidocaine patch, immediately remove the patch. Removing the source of the medication stops further systemic absorption and allows the drug in your bloodstream to be metabolized. Once the patch is removed, gently clean the area to ensure no residual medication remains on the skin surface.
Following patch removal, contact a healthcare provider promptly to report the symptoms. Systemic reactions signal that the dosage or application method may need adjustment, even if mild nausea resolves quickly. Your doctor will assess the severity of the reaction and decide if the treatment should be discontinued. Serious systemic reactions are rare but require professional evaluation.
When speaking with your doctor, discuss specifics, including the exact number of patches used, the total duration of wear, and whether the patch was applied to intact skin. Also mention any other topical pain relievers or medications you may be using, as some combinations can increase systemic exposure. This information helps the healthcare provider understand the likely cause of the discomfort.
Preventing Recurrence
To avoid recurrence, follow all dosing instructions precisely, including the maximum number of patches and the wear time, which is often 12 hours out of every 24. Never combine the use of a lidocaine patch with other topical pain relievers that contain similar ingredients unless instructed by your physician. Avoid applying any form of external heat, such as heating pads or sunlamps, to the area where the patch is placed to prevent uncontrolled absorption.