A person selling oleandrin as a cure can only be a person who has no concern for the sanctity of human life. IMHO.

Oleandrin is a toxic cardiac glycoside found in the poisonous plant, oleander (Nerium oleander L.).[1] As a main phytochemical of oleander, oleandrin is associated with the toxicity of oleander sap, and has similar properties to digoxin.[1]

Oleander has been used in traditional medicine for its presumed therapeutic purposes, such as for treating cardiac insufficiency. There is no clinical evidence that oleander or its constituents, including oleandrin, are safe or effective. Oleandrin is not approved by regulatory agencies as a prescription drug or dietary supplement.[1]

.....

Toxicity

Oleandrin has been reported to be lethal.[1] In one fatality, the blood concentration of oleandrin and a related cardiac glycoside from the oleander plant was estimated at 20 ng/ml.[9] In practice, there have been adult cases wherein 14-20 oleander leaves (of unknown oleandrin concentration) proved not to be fatal, but also a lethal case of a child that consumed only one leaf.[10]