Pharmacokinetics of Lidocaine Delivered

In: Anesthesia

6 Dec 2009

Lidocaine

INTRODUCTION

Children most often associate pain during a dental visit with the administration of local anesthetic. Pain and discomfort perceived by pediatric patients can be severe. In a survey of 119 children, 65 thought that a “shot” or “needle” hurt more than anything else that had ever happened to them.

One of the most common means of controlling the pain associated with local anesthetic injection is the use of topical anesthetic agents on the oral mucosa at the site of injection. Even though a topical anesthetic will not completely eliminate the sensations associated with needle penetration and anesthetic delivery, it can be a welcome adjunct in reducing the pain and anxiety of injections in children. online canadian pharmacy

One of the most critical factors in enhancing the efficacy of a topical anesthetic is maintaining prolonged intraoral mucosal contact. Most topical anesthetic agents used in dentistry come in gel form, which can be difficult to localize to a particular site and are easily diluted by saliva. Some of these complications can be avoided by using the DentiPatch® lidocaine transoral delivery system (Noven Pharmaceuticals, Miami, Fla), which has been approved by the United States Food and Drug Administration for clinical use in the production of mild, topical anesthesia of mucosal membranes in the mouth. The DentiPatch® is a mucoadhesive patch containing 46.1 mg of lidocaine (20% concentration). This patch is a site-specific drug delivery that purportedly maximizes the effect of lidocaine diffusing into a localized mucosal site to reduce the pain associated with injections. The onset of anesthesia may occur as early as 2.5 minutes after application, and the patch can be left in place for up to 15 minutes (DentiPatch® package insert, May 1999). Studies have shown it to be effective in reducing injection pain in adults compared with a placebo patch and in reducing verbal indicators of pain in children compared with 20% benzocaine gel.

Topical anesthetics can be a useful tool in the pediatric population; however, precautions must be taken to avoid adverse reactions associated with systemic local anesthetic toxicity. This is particularly important when using products such as the DentiPatch®, which contains a larger amount of anesthetic than most traditional gels. Although there are some data available on the plasma levels and toxicity associated with topical anesthetics, little of this data is applicable to the transoral patch, particularly in pediatric patients.

The safety data reported for the DentiPatch® show no serious adverse reactions, and systemic blood levels of the absorbed lidocaine were very low in adults. Plasma concentrations in adults after a 15-minute application of the 20% lidocaine patch were 21.80-22.3 ng/ mL. These concentrations were approximately 10 times lower than those measured after an injection of 1.8 mL of 2% lidocaine (36 mg) with 1:100,000 epinephrine (220 ng/mL at 15 minutes). Although these plasma levels fall within the safety range for adults, it is not known what plasma levels are obtained when the same dosage is used in children. The manufacturer notes that “Safety and effectiveness in children below the age of 12 years have not been established.”

Amide local anesthetics such as lidocaine are metabolized by microsomal enzymes in the liver, and unchanged drug and metabolites are excreted by the kidneys. Approximately 70 to 90% of lidocaine administered is biotransformed into various metabolites. The major metabolite, monoethylglycinexylidide (MEGX), is considered to be approximately 80 to 90% as potent as lidocaine, and it is thought to cause the central nervous system (CNS) depression observed in lidocaine toxicity. The accumulated plasma levels of lidocaine and its metabolites should be considered cumulatively when potential toxicity is being determined. Therefore, in this study, we have measured plasma levels of both lidocaine and MEGX. kamagra jelly uk

Complications associated with local anesthetic toxicity are rare, but severe toxicity has been reported in dental settings. Concern for toxicity in children is particularly important when local anesthetics are used in combination with sedative drugs. CNS toxicity is more likely at lower lidocaine plasma concentrations when certain CNS depressant medications, such as meperidine or chloral hydrate, are coadministered. These sedative drugs can lower the seizure threshold and could thereby augment the effects of lidocaine toxicity. The Ameri can Academy of Pediatric Dentistry recommends that a maximum dose-per-weight be calculated for each patient before all sedatives and local anesthetics are administered to avoid excessive doses. The lack of data for children on the absorption and subsequent plasma levels associated with the DentiPatch® makes it difficult to calculate an accurate dose.

Therefore, the purpose of this study was to determine whether lidocaine, when delivered transmucosally via a transoral mucosal patch, would produce plasma lidocaine and MEGX levels within the accepted margin of safety for children. kamagra soft tabs


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Blog invites submissions of review articles, reports on clinical techniques, case reports, conference summaries, and articles of opinion pertinent to the control of pain and anxiety in dentistry.