 It is excreted 47% in feces and 42% in urine.Less than 1% is excreted as unchanged brexanolone.Allopregnanolone is a pregnane (C21) steroid and is also known as 5α-pregnan-3α-ol-20-one, 3α-hydroxy-5α-pregnan-20-one, or 3α,5α-tetrahydroprogesterone (3α,5α-THP).