Benzocaine

Benzocaine is the ethyl ester of p-aminobenzoic acid (PABA), it is a local anesthetic commonly used as a topical pain reliever or in cough drops.

The effect of benzocaine and ketoprofen gels on pain during fixed orthodontic appliance treatment: a randomised, double-blind, crossover trial.[Pubmed:27468593]

Aust Orthod J. 2016 May;32(1):64-72.

AIMS: To compare the analgesic effect of topical Benzocaine (5%) and ketoprofen (1.60 mg/mL) after 2 mm activation of 7 mm long delta loops used for maxillary en-masse orthodontic space closure. SUBJECTS AND METHODS: Twenty patients (seven males, 13 females, 15-25 years of age, mean age of 19.5 years) participated in a randomised crossover, double-blind trial. After appliance activation, participants were instructed to use analgesic gels and record pain perception at 2, 6, 24 hours and 2, 3 and 7 days (at 18.00 hrs), using a visual analogue scale ruler (VAS, 0-4). Each patient received all three gels (Benzocaine, ketoprofen, and a control (placebo)) randomly, but at three different appliance activation visits following a wash-over gap of one month. After the first day, the patients were instructed to repeat gel application twice a day at 10:00 and 18:00 hrs for three days. The recorded pain scores were subjected to non-parametric analysis. RESULTS: The highest pain was recorded at 2 and 6 hours. Pain scores were significantly different between the three groups (Kruskal-Wallis test, p < 0.01). The overall mean (SD) pain scores for the Benzocaine 5%, ketoprofen, and control (placebo) groups were 0.89 (0.41), 0.68 (0.34), and 1.15 (0.81), respectively. The pain scores were significantly different between the ketoprofen and control groups (mean difference = 0.47, p = 0.005). All groups demonstrated significant differences in pain scores at the six different time intervals (p < 0.05) and there was no gender difference (p > 0.05). CONCLUSION: A significant pain reduction was observed following the use of ketoprofen when tested against a control gel (placebo). The highest pain scores were experienced in patients administered the placebo and the lowest scores in patients who applied ketoprofen gel. Benzocaine had an effect mid-way between ketoprofen and the placebo. The highest pain scores were recorded 2 hours following force application, which decreased to the lowest scores after 7 days.

Topical Benzocaine and Methemoglobinemia.[Pubmed:27754990]

Am J Ther. 2017 Sep/Oct;24(5):e596-e598.

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.

Effect of 5% benzocaine gel on relieving pain caused by fixed orthodontic appliance activation. A double-blind randomized controlled trial.[Pubmed:27659276]

Orthod Craniofac Res. 2016 Nov;19(4):190-197.

AIM: To compare the effectiveness of 5% Benzocaine gel and placebo gel on reducing pain caused by fixed orthodontic appliance activation. SETTING AND SAMPLE POPULATION: Thirty subjects (15-25 years) undergoing fixed orthodontics. METHODS AND MATERIALS: A randomized, double-blind, placebo-controlled and cross-over clinical trial study was conducted. Subjects were asked to apply a placebo gel and 5% Benzocaine gel, exchangeable in two consecutive appointments, twice a day for 3 days and mark their level of pain on a VAS scale. The pain severity was evaluated by means of Mann-Whitney U-test for comparing two gel groups, Kruskal-Wallis nonparametric test for overall differences and post hoc test of Dunnett for paired multiple comparisons. p-value was assigned <0.05. RESULTS: The overall mean value of pain intensity for Benzocaine and placebo gels was 0.89 and 1.15, respectively. The Mann-Whitney U-test indicated that there was no significant difference between overall pain in both groups (mean difference = 0.258 p < 0.21). For both groups, pain intensity was significantly lower at 2, 6 and 24 h compared with pain experienced at days 2, 3 and 7. CONCLUSION: Benzocaine gel caused a decrease in pain perception at 2 h compared with placebo gel. Peak pain intensity was at 2 h for placebo gel and at 6 h for Benzocaine gel, followed by a decline in pain perception from that point to day 7 for both gels.

Benzocaine shares a common receptor with all othe rLAs in the voltage-gated Na+ channel, with an IC50 of 0.8 mM tested with a potential of +30 mV.

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