Anbesol for babies: why worry?

23 Jun

Dapsone and topical anesthetic agents (benzocaine, the active ingredient in anbesol) are the most common causes of acquired methemoglobinemia

Acquired methemoglobinemia is a result of certain ingested drugs leading to a state of oxidized (ferric state Fe+++) of hemoglobin, which are unable to bind oxygen. The remaining hemoglobin groups have an increased oxygen affinity causing a left shift.

The overall result is a functional anemia.

There are two ways for methemoglobin to be reduced back to hemoglobin:

  1. NADH-dependent catalyzed by cytochrome b5 reductase (b5R)
  2. NADPH generated by glucose-6 phosphate dehydrogenase (G6PD), but in order for this pathway to be activated, an extrinsically administered electron acceptor is required (methylene blue and riboflavin)

Infants are more susceptible to the development of methemoglobinemia because their erythrocyte cytochrome b5 reductase activity is 50-60% of adult activity

Treatment includes administration of intravenous methylene blue, 1 to 2 mg/kg, given over five minutes


Submitted by K Estes.


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