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.

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.

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.

Topical Benzocaine and Methemoglobinemia.

Methemoglobinemia can cause life-threatening hypoxia associated with cyanosis and dyspnea not responsive to oxygen. We present a case of recurrent methemoglobinemia because of occult use of topical benzocaine to the vulva. A 47-year-old female with medical history of vulvar cancer and HIV undergoing chemoradiation was sent by the oncology clinic to the emergency department for worsening dyspnea, fatigue, hypoxia to 78% on room air, and gradual onset of cyanosis over the past week. A methemoglobin (MetHb) level was 49%. She received methylene blue, and repeat MetHb levels initially decreased but later increased to 56% despite continued treatment. Additional interviews with the patient revealed she was applying vagicaine (20% benzocaine), an over the counter preparation to the vulvar area for analgesia, and she continued application while hospitalized. She received a total of 6 mg/kg methylene blue and underwent vaginal lavage with 60 mL of sterile saline and cleansed with soapy water. Cyanosis, hypoxia, and dyspnea resolved, and the MetHb level decreased to 5.4% on the day of discharge. Benzocaine is a frequent cause of iatrogenic methemoglobinemia. In this case, additional medication inquiries were helpful in making the diagnosis. Many patients do not consider over-the-counter medications to be potentially harmful. Methemoglobinemia from occult topical benzocaine administration to the vulva is an uncommon exposure route. Occult medication use can be a source of methemoglobinemia.

An Uncommon Complication With Use of Topical Local Anesthetic Agents: Methemoglobinemia.

Although the use of topical local anesthetics is generally safe, several potentially fatal complications have been reported. Methemoglobinemia is a rare but potentially fatal complication. Methemoglobin is a naturally occurring oxidized metabolite of hemoglobin, and physiologic levels (<1%) are normal. Methemoglobinemia can be congenital or acquired. Several drugs including topical anesthetic agents like benzocaine can induce this condition. Sudden appearance of cyanosis, with a disproportionately better oxygen saturation of 85% after use of local anesthetics can be a helpful for diagnosis.

Frequency and trends of contact allergy to and iatrogenic contact dermatitis caused by topical drugs over a 25-year period.

BACKGROUND: Allergic contact dermatitis is the most common adverse reaction caused by topical drugs. OBJECTIVES: To study the demographic characteristics and lesion locations of patients with iatrogenic dermatitis, and to analyse contact allergy to active principles and trends in frequencies over the years. PATIENTS AND METHODS: Between 1990 and 2014, 14 911 patients were patch tested with the European baseline series. Patients with a presumed iatrogenic cause were often tested with a pharmaceutical series, and, if indicated, with photo-patch tests. Most were also tested with the topical products to which they had been exposed, along with their ingredients. RESULTS: Eight thousand three hundred and seventy-four (56%) patients tested positively, and 2600 (17.4%, 95%CI: 16.8-18.0%) of all patients suffered from iatrogenic contact dermatitis. The most important primary sites of dermatitis were the legs, face, and hands. The most common sensitizers included topical antibiotics, antiseptics, and corticosteroids. The most frequent baseline allergens in this subgroup were budesonide, neomycin, and benzocaine, although with a decreasing trend over the years. Many other allergens from different pharmacological classes were identified. CONCLUSIONS: With a prevalence of 17.4% of consecutive patients, iatrogenic contact dermatitis is a frequent diagnosis in patients attending a general patch test clinic, involving one-third of the patients with at least one positive reaction.

Methemoglobinemia Secondary to Topical Benzocaine Application to Gastrostomy Site.

Benzocaine is a common topical anesthetic that has the ability to induce methemoglobinemia (MetHgb) in large doses. We describe a 4-year-old girl who received a standard dose of topical benzocaine to her gastrostomy mucosa that resulted in rapid, severe MetHgb. She required intubation, mechanical ventilation, and multiple doses of methylene blue for treatment. The resultant tissue hypoxia from MetHgb caused profound confusion, cyanosis, and myocardial infarction. Although the patient did not sustain any permanent disability, this case demonstrates the need for emergency providers to rapidly identify and treat MetHgb to reverse tissue hypoxia and prevent long-term sequelae.

Central cyanosis on a psychiatric unit treated at the Salford Royal Hospital.

We describe a case of acquired methaemoglobinaemia due to frequent use of the 'legal high' known as 'Pink Panthers'. This contains 5,6-Methylenedioxy-2-aminoindane and 2-Aminoindane, both amphetamine analogues with the potential to cause methaemoglobinaemia. Furthermore, the most common 'cutting agent' for legal highs in the UK is benzocaine, also known to cause methaemoglobinaemia. Given the increasing prevalence of legal highs, particularly those containing added benzocaine, such presentations may become more common. Furthermore, in one case series, benzocaine gel used for toothache was the second most common reason for hospitalisation due to acquired methaemoglobinaemia after dapsone use. Indeed, the Federal Drug Agency has issued as public warning as to the risk of these products. We therefore think that clinicians and the public should be made more aware of the risk associated with such agents.

MAM-2201 (analytically confirmed) intoxication after "Synthacaine" consumption.

Excitatory behavior, xerostomia, chest pain, severe dyspnea, tachycardia (150 beats/min), and mild hypertension (160/80 mm Hg) without ECG abnormalities were observed in a 20-year-old subject 6 hours after nasal insufflation (snorting) of a "legally" obtained white powdered substance sold as Synthacaine. A serum sample was found to contain MAM-2201 (11 ng/mL), a synthetic cannabinoid receptor agonist, and benzocaine. The patient's symptoms improved after administration of diazepam and intravenous fluids. Synthacaine was sold as legal cocaine, suggesting the user can expect an effect like that of cocaine. The pharmacologic receptor profile and chemical structure of MAM-2201 is similar to the synthetic cannabinoid receptor agonists AM-2201 and JWH-122 (2 potent synthetic cannabinoid receptor agonists with high affinity to cannabinoid receptors).

Lidocaine contact allergy is becoming more prevalent.

BACKGROUND: Allergic contact dermatitis (ACD) to lidocaine is rising in prevalence. This is due to a growing number of over-the-counter (OTC) products containing topical amide and ester anesthetics. The phenomenon poses a real threat to the authors' surgical anesthetic options. OBJECTIVE: To investigate the epidemiology of topical anesthetic ACD in British Columbia, Canada and provide an approach for clinicians to deal with this problem. MATERIALS AND METHODS: A retrospective chart review of 1,819 patients who underwent patch testing at the University of British Columbia Contact Dermatitis Clinic between January 2009 and June 2013 was completed. The authors also performed a detailed review of Canadian OTC preparations containing lidocaine in 2013. RESULTS: The prevalence of ACD to local anesthetics is significant at 2.4%. The most common allergen is benzocaine (45%) followed by lidocaine (32%) and dibucaine (23%). CONCLUSION: The proportion of ACD caused by lidocaine is higher than expected. This is likely secondary to an increase in OTC medicaments containing lidocaine. Patients who are patch test-positive to a local anesthetic should be challenged intradermally to confirm clinical relevance. Because ACD is a delayed Type IV hypersensitivity reaction (localized dermatitis), the risk of anaphylaxis is not a concern.

Patch testing with a textile dye mix--a multicentre study.

BACKGROUND: Disperse dyes are well-known contact sensitizers. However, they are not included in the majority of commercially available baseline patch test series. OBJECTIVES: To investigate the outcome of patch testing with a textile dye mix (TDM) consisting of eight disperse dyes at dermatology clinics in various countries. PATIENTS/MATERIALS/METHODS: Two thousand nine hundred and seven consecutive dermatitis patients at 12 dermatology clinics representing nine countries were tested with a TDM at 6.6%, consisting of Disperse Blue 35, Disperse Yellow 3, Disperse Orange 1 and 3, and Disperse Red 1 and 17, all at 1.0%, and Disperse Blue 106 and Disperse Blue 124, each at 0.3%, provisionally included in the baseline series. Eighty-seven per cent of the patients allergic to the TDM were also tested with the eight separate dyes. RESULTS: Contact allergy to TDM was found in 108 patients (3.7%). The frequency of contact allergy varied from 2.1% to 6.9% in different centres. Simultaneous reactivity to p-phenylenediamine was found in 57 of the TDM-positive patients (53%). The most frequent dye allergen among the TDM-positive patients was Disperse Orange 3. The contact allergy could have explained or contributed to the dermatitis in approximately one-third of the patients for whom clinical relevance of the TDM contact allergy was recorded. CONCLUSIONS: The TDM should be considered for inclusion in the European baseline series.

Occupational contact dermatitis in hairdressers: an analysis of patch test data from the Danish contact dermatitis group, 2002-2011.

BACKGROUND: Occupational contact dermatitis among hairdressers is frequent, owing to daily exposure to irritants and allergens. OBJECTIVES: To identify sensitization to the most common allergens associated with the occupation of hairdressing. METHODS: Patch test results of 399 hairdressers and 1995 matched controls with contact dermatitis, registered by the Danish Contact Dermatitis Group between January 2002 and December 2011, were analysed. All patients were patch tested with the European baseline series, and hairdressers were additionally tested with the hairdressing series. RESULTS: Occupational contact dermatitis (p < 0.001) and hand eczema (p < 0.001) were observed significantly more often among hairdressers than among controls. Atopic dermatitis was less commonly observed among hairdressers (21.3%) than among controls (29.4%) (p < 0.01). Allergens from the European baseline series with a statistically significant association with the occupation of hairdressing were p-phenylenediamine, thiuram mix, and benzocaine. Frequent sensitizers from the hairdressing series were ammonium persulfate, toluene-2,5-diamine, 3-aminophenol, and 4-aminophenol. Cysteamine hydrochloride and chloroacetamide emerged as new sensitizers. CONCLUSIONS: These results indicate a healthy worker effect among hairdressers diagnosed with eczema. Ammonium persulfate and p-phenylenediamine remain frequent sensitizers in hairdressers with contact dermatitis. Cysteamine hydrochloride and chloroacetamide should be included in future surveillance studies.

Acute dyspnea in a postpartum patient.

Topical benzocaine sprays used to relieve perineal pain in postpartum patients can, rarely, lead to methemoglobinemia. In patients with other medical issues, such as anemia, methemoglobinemia can become symptomatic, causing acute dyspnea and potentially becoming life-threatening.

[The development of severe methemoglobinemia in patients receiving "Almagel A"].

This clinical case and the literature review show possible development of methemoglobinemia due to the use of local anesthetics, included in drugs for the gastrointestinal diseases treatment, in particular benzocaine, which is the methaemoglobin forming agent. These drugs are common and often taken by the patients themselves without any control. The aim of our paper is to draw the attention of physicians to the risk of the widely known drug administration which can be purchased without a prescription.

Contact allergy to local anaesthetics-value of patch testing with a caine mix in the baseline series.

BACKGROUND: Contact allergy to local anaesthetics is relatively common. Patch testing with benzocaine in the European baseline series is recommended for diagnosis, even though a caine mix has been previously suggested to be superior. OBJECTIVES: To assess the frequency and patterns of contact allergy to local anaesthetics by using a caine mix (benzocaine, tetracaine, and cinchocaine) in the baseline series, and evaluate its efficiency as compared with benzocaine alone. METHODS: We reviewed the results of 2736 patch tests performed between 2000 and 2010, identifying patients with positive reactions to caine mix or to one of seven local anaesthetics. RESULTS: One hundred and twelve patients (4.1%) had at least one allergic reaction to local anaesthetics; 86 were tested with all seven local anaesthetics, resulting in 71 reactions in 53 patients. Cinchocaine gave the most reactions (50.7%); these occurred as a single reaction in 83.3% of patients, mostly with current or past relevance (97%). Benzocaine represented 22.5% of reactions, many of which were non-relevant (44%) or resulting from cross-reactions with para-compounds. CONCLUSIONS: Almost 70% of allergic reactions to local anaesthetics would have been missed if benzocaine had been used as a screening allergen. This study supports a recommendation to replace benzocaine with a caine mix containing cinchocaine in the baseline patch test series.