In 1981 an unnamed European manufacturer produced 44 kg of iboga extract. The entire stock was purchased by Carl Waltenburg, who distributed it under the name "Indra extract" and used it in 1982 to treat heroin addicts in Christiania , Denmark, a squatter village where heroin addiction was widespread.  Indra extract was available for sale over the Internet until 2006, when the Indra web presence disappeared. Various products are currently sold in a number of countries as "Indra extract", but it is unclear if any of them are derived from Waltenburg's original stock. Ibogaine and related indole compounds are susceptible to oxidation over time.  
DHEA is transformed into DHEA-S by sulfation at the C3β position via the sulfotransferase enzymes SULT2A1 and to a lesser extent SULT1E1 .    This occurs naturally in the adrenal cortex and during first-pass metabolism in the liver and intestines when exogenous DHEA is administered orally. [ citation needed ] Levels of DHEA-S in circulation are approximately 250 to 300 times those of DHEA.  DHEA-S in turn can be converted back into DHEA in peripheral tissues via steroid sulfatase (STS).