Human Pharmacokinetics and Safety of Boric Acid
Using an in vitro technique it has been demonstrated that water-emulsifying and hydrophobic ointments containing boric acid liberate only minute amounts (1–6%) within 24h compared with the nearly total liberation from a jelly. When an amount of boric acid containing ointment is swallowed, the absorption is only slightly delayed compared with a similar intake when dissolved in water, and in both cases nearly total excretion is found in the urine within 96 h. The halflife (t 1/2β ) is 21h (mean, 7 adult men). The pharmacokinetics rule out the risk of cumulative poisoning with topical preparations containing low amounts of boric acid. The use of water-emulsifying ointments containing up to 3% boric acid should be safe, even for repeated daily use in the napkin region.
Key wordsBoric acid Water-emulsifying ointments Cosmetic safety –Pharmacokinetics Skin absorption Gastrointestinal absorption Urinary excretion Napkin area protection
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