An overview of local anesthetics in over-the-counter products.

Over-the-counter (OTC) local anesthetics have historically been used to alleviate pain in several common conditions including toothache and sore throat. With a rise in chronic conditions and an aging population, there has been an increase in associated chronic pain-related disorders. Individuals with chronic pain often seek OTC treatments for quick and accessible pain relief. There are several common OTC local anesthetics, including benzocaine, lidocaine, and dibucaine, which are readily available to patients in several formulations. In order to appropriately advise patients on the use of local anesthetics, it is important to understand their key characteristics, including the mechanism of action, clinical properties, pharmacokinetics, clinical applications, and adverse reactions, which may occur.

Acquired Methemoglobinemia in the Surgical Intensive Care Unit.

Acquired methemoglobinemia is a potentially lethal medical condition caused by exposure to oxidizing xenobiotics, including antibiotics such as dapsone and inhaled anesthetics such as benzocaine. In this case report, we describe two presentations of acquired methemoglobinemia which presented to our surgical intensive care unit within one month. This highlights the potential connection between an emergent surgery or procedure and the development of methemoglobinemia in an environment where it is presumed that this condition would be extremely rare. High clinical suspicion for methemoglobinemia is warranted if the patient develops cyanosis or a decreased oxygen saturation unresponsive to supplemental oxygen when another etiology is not identifiable. If methemoglobinemia is suspected, a direct measurement of blood methemoglobin levels can be obtained to confirm the diagnosis. Prompt treatment with intravenous methylene blue is highly effective.

Hemolysis and acquired methemoglobinemia associated with lidocaine and benzocaine topical application: a case report.

BACKGROUND: Topical anesthetics are commonly used over the counter, and one of the adverse effects of these medications is methemoglobinemia, which is a serious and life-threatening condition. CASE PRESENTATION: We describe a 25-year-old Persian male presenting with generalized weakness, dizziness, headache, and cyanosis. In addition, he had genital warts starting 3 weeks ago, which were self-treated with podophyllin, resulting in itching and pain. He used over-the-counter topical anesthetics, including benzocaine and lidocaine, to reduce the symptoms. According to the lab data, signs and symptoms of methemoglobinemia and hemolysis were diagnosed. Considering the hemolysis, ascorbic acid was used for treatment. The patient was discharged after 5 days with normal arterial blood gas and pulse oximetry and no signs and symptoms. CONCLUSION: This case highlights that self-administration of some topical anesthetics may lead to potentially fatal conditions.

Asymptomatic benzocaine spray-induced methaemoglobinaemia in preoperative sedation for oesophagogastroduodenoscopy.

Methaemoglobinaemia is defined as elevated methaemoglobin in the blood which is characterised by conversion of some of the reduced ferrous iron elements [Fe2+] to the oxidised ferric [Fe3+] form which does not have capacity to bind and transport oxygen resulting in functional anaemia. Causes can be genetic mutations or acquired by medications such as dapsone, nitrates or benzocaine. Benzocaine is currently being used as a topical anaesthetic agent before certain procedures. We report a case of benzocaine spray-induced methaemoglobinaemia in a patient who underwent oesophagogastroduodenoscopy for evaluation of upper gastrointestinal bleeding.

Benzocaine-induced methaemoglobinaemia in an adolescent with sepsis.

Methaemoglobinaemia is a potentially life-threatening condition characterised by hypoxaemia, cyanosis, pallor, fatigue, metabolic acidosis, headache and in severe cases, coma or death. Topical anaesthetics have been reported to cause methaemoglobinaemia. Topical benzocaine was specifically implicated in roughly 66% of anesthetic-induced methaemoglobinaemia cases in a large systematic review in adults. This complication has occurred often in adult patients with pre-existing comorbidities resulting in diminished use in children overall with only few paediatric cases reported worldwide. Additionally, there is growing evidence of a link between sepsis and methaemoglobinaemia due to increased circulating nitrous oxide from infectious pathogen metabolism. In this report, we discuss a case of a 16-year-old young boy, being evaluated for suspected endocarditis, presenting with acute methaemoglobinaemia after use of topical benzocaine spray for transesophageal echocardiogram. This case exemplifies the importance of blood gas with co-oximetry testing in all cases of refractory hypoxemia who have had procedures requiring topical anaesthetics.

Benzocaine-related methaemoglobinemia after transoesophageal echocardiography: a rare, life-threatening complication.

Methaemoglobinemia is an uncommon but potentially life-threatening complication of topical benzocaine use that requires prompt identification in patients who undergo transoesophageal echocardiography (TEE). In this case, a 21-year-old patient who had sustained a stroke with residual right-sided weakness a few days prior to presentation underwent TEE to evaluate for intracardiac shunt. She required intubation as part of her poststroke care with some instrumentation to the posterior oropharynx. Shortly after TEE, the patient experienced sudden onset respiratory distress and hypoxia that did not improve with supplemental oxygen. Chest X-ray did not reveal any acute cardiopulmonary process. Arterial blood gas co-oximetry panel with methaemoglobin level confirmed the diagnosis of methaemoglobinemia. The patient promptly received methylene blue, recovered quickly and did not have any additional episodes of hypoxia.

Methaemoglobinaemia from Vagisil creme in a 50-year-old woman.

Methaemoglobinaemia is a life-threatening condition that results from increased methaemoglobin production. As methaemoglobin is unable to reversibly bind to oxygen potentially lethal hypoxia and functional anaemia can occur. Benzocaine can be used as a topical anaesthetic and can be found in many nonprescription preparations marketed for self-application. It is known to cause methaemoglobinaemia in rare cases but most reports describe the complication occurring during endoscopy procedures. Methaemoglobinaemia occurring after topical benzocaine use on the perineum of a perimenopausal woman is exceedingly rare. A 50-year-old woman with methaemoglobinaemia secondary to the perineal application of over-the counter Vagisil (benzocaine 20% and resorcinol 3%- an antiseptic and disinfectant, respectively) presented to the emergency department. She had been using Vagisil for severe, chronic vaginal itching. While methaemoglobinaemia secondary to excessive use of over-the-counter medications such as Vagisil creme is exceedingly rare, it should be included in the differential diagnosis.

Comparing the Efficacy of a Compound Topical Anesthetic Versus Benzocaine: A Pilot Study.

To compare the effectiveness of a combination of 10% lidocaine, 10% prilocaine, and 4% tetracaine versus 20% benzocaine for use as a topical anesthetic agent prior to dental injections. A double-blind randomized prospective clinical trial was conducted with 26 participants receiving a topical anesthetic of 20% benzocaine (control) and 26 participants receiving a compound topical anesthetic mixture of 10% lidocaine, 10% prilocaine, and 4% tetracaine (experimental) prior to a maxillary infiltration injection. The procedure was conducted by 1 operator with the Wand® injection system. Pain was assessed directly with visual analog scale (VAS) scores and indirectly by measuring changes in heart rate at 4 different time points. Complications associated with the application of the topical anesthetics were also assessed. The experimental group had a significantly higher mean VAS score of 19.5 ± 19.7 mm versus 14.2 ± 14.6 mm for the control group (p < .001). No significant differences in heart rate at any of the 4 measured time points compared with baseline were noted for either group. The experimental group had a significantly higher incidence of complications, including tissue sloughing, when compared with the control group (p < .001). Participants in the control group reported significantly lower VAS scores than those in the experimental group. Both types of topical anesthetic showed similar impacts on alterations to heart rate. No benefits were seen with the use of 10% lidocaine, 10% prilocaine, and 4% tetracaine as a topical anesthetic prior to a maxillary infiltration of local anesthetic when compared with 20% benzocaine.

Efficacy of Benzocaine, Eugenol, and Menthol as Anesthetics for Freshwater Angelfish.

For the production and commercialization of ornamental fish species, it is indispensable to collect biometric data that facilitate the selection of animals for trade and genetic improvement of the stock. However, during the handling process, fish receive more stress if proper anesthetics are not used. Thus, application of appropriate anesthetics is an important tool for minimizing stress in animals. The objective of this study was to determine the effective concentrations of benzocaine, eugenol, and menthol for achieving anesthesia in Freshwater Angelfish Pterophyllum scalare and to develop induction and recovery response curves for different concentrations of these anesthetics. In total, 75 fish were exposed to five concentrations of the three anesthetics in a completely randomized design: benzocaine at 60, 85, 110, 135, and 160 mg/L; eugenol at 40, 80, 120, 160, and 200 mg/L; and menthol at 50, 75, 150, 200, and 250 mg/L. Each concentration (5 fish/concentration) consisted of five replicates, with each replicate represented by a single fish. The results indicated that the tested substances met the criteria of anesthetic efficiency. The effective concentrations of benzocaine, eugenol, and menthol for the anesthesia of Freshwater Angelfish were identified as 89.25, 90.6, and 92.1 mg/L, respectively.

A Case Report of Benzocaine-Induced Methemoglobinemia.

Methemoglobinemia is a serious medical condition characterized by the disrupted binding of oxygen to iron on hemoglobin, with a consequent impaired oxygen delivery to body tissues. Various drugs including the local anesthetics such as benzocaine can cause acquired methemoglobinemia. The reported case describes methemoglobinemia that occurred in association with the use of topical benzocaine spray and lozenges in a previously healthy 51-year-old female who had undergone colon surgery to remove a bleeding polyp. Pulse oximetry revealed the patient was hypoxic and a measured methemoglobin (MetHB) serum concentration was 32.4%, well above the normal of less than 2%. Treatment with intravenous methylene blue resulted in a rapid improvement in the patient's respiratory status. The case emphasizes the need for practitioners to appreciate that topical benzocaine products can cause potentially fatal methemoglobinemia.

What are pharmacists recommending for infant teething treatment?

OBJECTIVES: In 2011, the Food and Drug Administration issued a warning to avoid the use of any benzocaine-containing products for infant teething treatment owing to a risk of methemoglobinemia. Several benzocaine-containing products targeted for infant teething are currently available over the counter. Pharmacists are commonly asked for medical advice in the community, and there is no current literature evaluating what pharmacists are recommending for infant teething. The objectives of this study were to evaluate what pharmacists are currently recommending for infant teething treatment and assess what percentage would inappropriately recommend a benzocaine-containing product. METHODS: From March to June 2016, a 16-item in-person paper-and-pen questionnaire was administered to 200 pharmacists in the San Francisco Bay area at 115 outpatient over-the-counter pharmacies. Questions included demographic information, work and educational background, infant teething recommendations, and preferred educational resources. RESULTS: The overall response rate was 94.3%. One-half (50.5%) of the pharmacists' approaches to infant teething treatment was to recommend a nondrug option first and then, if needed, an over-the-counter medication. A majority (63.0%) of the pharmacists surveyed would inappropriately select a benzocaine-containing product. CONCLUSION: Despite warnings, the majority of pharmacists would still inappropriately recommend a benzocaine-containing product for treatment of infant teething. Further education is warranted to ensure that all pharmacists, health care providers, and consumers are aware of the potential harm of benzocaine use in infants.