"Ayahuasca is a traditional medicine central to the lives of indigenous peoples throughout the Amazon river basin. Almost a decade ago, Loren Miller of the International Plant Medicine Corporation applied to the US government to be recognized as the "inventor" of ayahuasca. Although ayahuasca has been produced and used by Amazonian peoples since time immemorial, the US Patent and Trademark Office agreed to grant Miller a patent, a form of intellectual property that conveys exclusive rights to produce and trade the patented item, at least within the country where the patent is granted.
Currently, the patent on ayahuasca applies only to a few western countries, including the U.S.. However, when Amazonian peoples first learned about the patent in the summer of 1996, the Ecuadorian government was considering entering into a trade agreement with the U.S. that would have led to patents granted in the US being extended to Ecuador. Although popular organizing by indigenous peoples and environmentalists temporarily defeated that trade deal, the threat remains that some day the patent on ayahuasca may be recognized and enforced in the Amazon, leading to restrictions on indigenous peoples' use of their sacred plant.
And regardless of whether or not this threat ever turns into reality, granting a foreign corporation intellectual property rights over ayahuasca represents a direct denial of indigenous peoples' rights over their own knowledge and innovation. As stated by COICA, the coordinating body for indigenous peoples' organizations in the Amazon region, "ayahuasca is a fundamental ingredient of the religious ceremonies and of healing for our people, and this patent is a real affront to the over four hundred cultures that populate the Amazon Basin.""
Eventually the US Patent and Trademark Office overturned the patent in 1999 on the basis of prior art. For the academically inclined some further information on the story can be found in Fecteau, L.M. (2001). The ayahuasca patent revocation: Raising questions about current US patent policy. Boston College Third World Law Journal. 69, 74-75.
I believe the patent was reinstated in 2001 following an appeal by the patent holder. I assume it lapsed in 2006? But if anyone knows better do let me know.