A murderer lurks in your neighborhood. It’s Nerium oleander, and it’s everywhere. Great swaths of it envelop LA freeways. It’s littered across backyards, and encircles parking lots. And it’s deadly poisonous to humans, animals and especially kids so don’t taste it, don’t sniff it, don’t even touch it, OMG I brushed against it AAAHHHH!!!
Actually, it may not be quite that big a deal. Although all parts of the oleander plant are toxic, and quite a lot of people are treated for oleander poisoning in the US, there have actually been only a handful of adult deaths from oleander poisoning in the last 25 years. Most of these were deliberate self-poisonings, with the exception of a young couple of vegans who got lost while hiking and ate a whole mess of oleander leaves. Estimates I’ve seen suggest that a lethal dose to a child would be about one whole leaf, and several leaves for an adult, and the potential for poisoning by skin contact is minimal. So, while you should definitely watch out for your kids around oleander, you don’t have to be quite as afraid of it as I always thought. The urban legend about a troop of boy scouts who died after roasting their marshmallows on oleander sticks, for example, is almost certainly bunk.
That having been said, getting sick from incidental leaf consumption would be no fun, and oleander really is everywhere, so here’s what to look for: it’s a tall shrub, 2-6m high, often used in neighborhood hedges. If you live anywhere in southern California (or some places in northern California, like along the 80 between Davis and Sacramento), you’ve seen it lining the freeways and medians.
The flowers are vibrantly pink or red or sometimes white, and grow in bunches. Most distinctive are the leaves, which are dark green and leathery, and shaped like thin daggers about 4-8 inches long (there’s that assassin imagery again). The leaves and flowers are poisonous because of several compounds, but notably the cardiac glycoside oleandrin/oleandrine and its metabolites. Cardiac glycosides interfere with the Na+/K+ ATPase pump in heart muscle cells, throwing off the balance of ions inside the cell, and ultimately leading to it contracting faster and more strongly than it’s supposed to. So oleander poisoning can result in irregular heartbeat, poor circulation, seizures, coma, and death.
While I was in college near LA, I encountered a rumor that oleanders were heavily planted along the local freeways because they were able to metabolize carbon monoxide (CO) emissions from cars, thus cleaning the air. Turns out, the rumor may have had it exactly backwards. A whole litany of plants, maybe all of them, can take up and metabolize small amounts of CO from the air—this was determined by Canadian botanists Bidwell and Fraser in the 1970s, who put radioactive C14-labeled CO into the air around plant samples, and recovered the C14 label from the plant later. But the only study that talks specifically about oleander and CO is by Fischer and Luttge in 1978, who found that oleander was actually a net producer of CO through C1 metabolism of glucose. That is to say, they might take up a little CO from the air, but then they actually make more of it in their own metabolism. So no air-quality help there.
Extra Nitty-Gritty: Plant crossover!
One of the treatments for oleander poisoning is a digoxin immune fab, using antibodies raised against a similar glycoside from the plant foxglove called digoxin. Apparently, oleandrin and digoxin are similar enough that antibodies raised to the latter will also bind the former. The antibodies work by binding to the glycoside and preventing it from reaching its target in the body and causing harm–it’s the same principle used to make snake or spider antivenom.
Anything oleander is good for?
In previous centuries, oleander was used as an herbal medicine to treat everything from headaches to eczema, which makes me queasy to think about. Since digoxin is used therapeutically for some heart conditions, I thought oleandrin might be the same, but its therapeutic index seems pretty limited in that context. However, it does appear that the same Na+/K+ ATPase pump interfering properties that make oleandrin so dangerous to heart cells also make it effective at killing off some kinds of cancer cells when used in concert with chemo- or radiotherapies. But a drug based on oleandrin called Anvirzel stalled after Phase I clinical trials in Ireland (due to poor performance–no reduction in solid tumors was seen but side effects were, and at least one company trying to inflate claims of its efficacy and continue to sell it got in serious trouble with the FDA). Now it’s the subject of an alarming cancer home-remedy fad based on making oleander extract at home. People, please don’t poison yourselves!
Want more detail? Here are the references:
Fab antibody fragments: some applications in clinical toxicology. Flanagan RJ, Jones AL. Drug Saf. 2004;27(14):1115-33.
Cardiac glycosides in cancer research and cancer therapy. Winnicka K, Bielawski K, Bielawska A. Acta Pol Pharm. 2006 Mar-Apr;63(2):109-15.
Phase 1 trial of Anvirzel in patients with refractory solid tumors. Mekhail T, Kaur H, Ganapathi R, Budd GT, Elson P, Bukowski RM. Invest New Drugs. 2006 Sep;24(5):423-7.