Benzocaine undergoes ester hydrolysis to form 4-aminobenzoic acid, acetylation to form acetylbenzocaine, or N-hydroxylation to form benzocaine hydroxide. 4-aminobenzoic acid can be acetylated or acetylbenzocaine can undergo ester hydrolysis to form 4-acetaminobenzoic acid.
The effect of dose and enzymatic inhibition on the percutaneous absorption and metabolism of benzocaine was studied in vitro in the hairless guinea pig. At the dose level of 2 ug/sq cm, benzocaine was rapidly absorbed and extensively metabolized (80%) by acetyltransferase. As the applied dose of benzocaine was increased to 40 and 200 ug/sq cm, N-acetylation of benzocaine decreased to 44 and 34%, respectively, suggesting saturation of the acetyltransferase system. Total 14(C) absorption after benzocaine application was not significantly different between control and enzyme-inhibited skin and therefore does not appear to be affected by the extent of benzocaine metabolism during percutaneous penetration. Skin provides a significant first-pass metabolic effect for therapeutic doses of percutaneously absorbed benzocaine, and the primary metabolite formed, acetylbenzocaine, is biologically active.
Benzocaine binds to sodium channels and reversibly stabilizes the neuronal membrane which decreases its permeability to sodium ions. Depolarization of the neuronal membrane is inhibited thereby blocking the initiation and conduction of nerve impulses.
来源:Toxin and Toxin Target Database (T3DB)
毒理性
致癌物分类
对人类无致癌性(未列入国际癌症研究机构IARC清单)。
No indication of carcinogenicity to humans (not listed by IARC).
Allergic reactions occur with ester local anaesthetics (like benzocaine) because of the PABA structure. Benzocaine also is a well-known cause of methemoglobinemia. [Wikipedia]. Methemoglobinemia has been reported with benzocaine in oral overdose. (L1861)
◉ Summary of Use during Lactation:Topical benzocaine has not been studied during breastfeeding, but is unlikely to affect her breastfed infant if it is applied away from the breast. Benzocaine should not be applied to the breast or nipple, because the infant may ingest the drug during nursing and it has been associated with severe methemoglobinemia in children under 2 years of age.
◉ Effects in Breastfed Infants:Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk:Relevant published information was not found as of the revision date.
◈ What is benzocaine?
Benzocaine is a topical local anesthetic. Local anesthetics are used to numb areas of the body for short periods of time. Benzocaine can be found in some over the counter pain relieving products.Very little of benzocaine is likely to be absorbed across the skin. Since so little of the medication passes into the body, the amount that would reach a developing baby, if any, is unlikely to be a high amount.
◈ I take benzocaine. Can it make it harder for me to get pregnant?
Studies have not been done to see if benzocaine use could make it harder to get pregnant.
◈ Does taking benzocaine increase the chance for miscarriage?
Miscarriage can occur in any pregnancy. Studies have not been done to see if benzocaine increases the chance for a miscarriage.
◈ Does taking benzocaine increase the chance of birth defects?
Every pregnancy starts out with a 3-5% chance of having a baby with a birth defect. This is called background risk. Two reports did not find a greater chance for birth defects among 73 children whose mothers reported using benzocaine in the first trimester of pregnancy.Since very little benzocaine is expected to be absorbed through the skin it is unlikely that a significant amount would reach the developing baby. Given the topical use of this medication, it is unlikely there would be an increased chance for birth defects if used as directed.
◈ Does taking benzocaine in pregnancy increase the chance of other pregnancy related problems?
Studies have not been done to see if benzocaine increases the chance for pregnancy-related problems such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces at birth).
◈ Does taking benzocaine in pregnancy affect future behavior or learning for the child?
Studies have not been done to see if benzocaine can cause behavior or learning issues for the child.
◈ Breastfeeding while taking benzocaine:
Benzocaine has not been well studied for use during breastfeeding. However, as long as benzocaine is not applied to the breast or nipple so that a nursing child could not get it in their mouth, it should be okay to continue to breastfeed. Wash hands well after using benzocaine. Talk to your healthcare providers about all of your breastfeeding questions.
◈ If a male takes benzocaine, could it affect fertility (ability to get partner pregnant) or increase the chance of birth defects?
Studies have not been done to see if benzocaine could affect male fertility or increase the chance of birth defects. In general, exposures that fathers or sperm donors have are unlikely to increase the risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
Branchial and urinary elimination of benzocaine residues was evaluated in adult rainbow trout, Oncorhynchus mykiss, given a single dorsal aortic dose of 14(C)-benzocaine hydrochloride. Branchial elimination of benzocaine residues was rapid and accounted for 59.2% of the dose during the first 3 h after dosing. Renal elimination of radioactivity was considerably slower; the kidney excreted 2.7% dose within 3 h and 9.0% within 24 hr. Gallbladder bile contained 2.0% dose 24 hr after injection. Of the radioactivity in radiochromatograms from water taken 3 min after injection, 87.3% was benzocaine and 12.7% was N-acetylated benzocaine. After 60 min, 32.7% was benzocaine and 67.3% was N-acetylated benzocaine. Of the radioactivity in radiochromatograms from urine taken 1 hr after dosing, 7.6% was para-aminobenzoic acid, 59.7% was N-acetylated para-aminobenzoic acid, 19.5% was benzocaine, and 8.0% was N-acetylated benzocaine. The proportion of the radioactivity in urine changed with time so that by 20 hr, 1.0% was para-aminobenzoic acid and 96.6% was N-acetylated para-aminobenzoic acid. Benzocaine and a more hydrophobic metabolite, N-acetylated benzocaine, were eliminated primarily through the gills; renal and biliary pathways were less significant elimination routes for benzocaine residues.
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