Here, the oleandrin synthesis (along with other metabolites) can be stimulated in untransformed plant cell cultures with supplementation of phytohormone.

Transgenic cultures of Agrobacteria are able to synthesize great quantities of oleandrin and other metabolites of the oleander plants, fit for pharmaceutical purposes.

[5] Because of its properties as a cardiac glycoside, oleandrin interferes in some essential processes within the cell, the most important of these being the inhibition of the Na-K ATPase.

[6][7] Apart from being a potent toxic compound, there are no results on oleandrin from human clinical research that support its use as a treatment for cancer or any disease.

[1] Use of oleander may cause contact dermatitis, headache, nausea, lethargy, and high blood levels of potassium, with symptoms appearing within a few hours of ingestion.

[1] In one fatality, the blood concentration of oleandrin and a related cardiac glycoside from the oleander plant was estimated at 20 ng/ml.

[1] The gastrointestinal effects can consist of nausea, abdominal pain, and vomiting, as well as higher salivation and diarrhea (which may contain blood).

Also, xanthopsia (yellow vision), a burning sensation of the mucous membranes of the eyes, and gastrointestinal tract and respiratory paralysis can occur.

These symptoms can include drowsiness, tremors, or shaking of the muscles, seizures, collapse, and even coma that can lead to death.

[11] A direct analytic technique like liquid chromatography-electrospray tandem mass spectrometry is used when there are medical or legal issues.

[22][23] Patients receiving an adequate dose of anti-digoxin Fab show a good response, resolving serious arrhythmias in two hours in fifty percent of the cases.

Treated patients showed a rapid increase in heart rate and a significant decline in serum potassium levels.

[25][26][27][28] These claims were widely regarded by scientists as dubious, misleading, and alarming, as well as having no clinical proof of safety or effectiveness.

[25][28][29] The unproven claims of benefit further caused concern among scientists that the Trump administration might force unwarranted FDA approval of oleandrin as a safe and effective treatment for COVID-19 infection.