Could eardrops containing boric acid be safely used in pregnant women?

Fråga: Could eardrops containing boric acid be safely used in pregnant women?

Sammanfattning: Boric acid may be teratogenic and its use should be avoided during pregnancy.

Svar: In animal studies, exposure to high doses of boric acid has repeatedly been associated with axial skeleton malformations and the mechanism presumably involves inhibition of histone deacetylases in the foetus (1). Human data are very scarce, but two case control-studies have demonstrated a significantly increased incidence of malformations in children whose mothers had been exposed to boric acid vaginally during the pregnancy (2). It is not evident if the site of administration in these women increased the foetal exposure through local diffusion or if the exposure was mainly due to systemic absorption. However, the dose used vaginally (60 mg/d) is approximately equivalent to 1.5 mL eardrops (4%) per day and boric acid is readily absorbed through inflamed skin (3). Hence, local administration in an external auricular meatus affected by external otitis may lead to systemic exposure rather similar to that in the pregnant women in the abovementioned studies.