From the end of that article: "While the experiment is quoted as evidence of LSD's toxicity, it seems most likely that the Thorazine or the combination of drugs killed Tusko, not the acid. Lending credence to this, in 1984 psychologist Ronald K Siegel repeated the experiment with two elephants, using LSD only. Both survived."
Although the elephant got a considerably larger dose (297 mg!!) than people would, and the experimenters handled the situation poorly.
http://www.theguardian.com/science/2004/feb/26/research.scie...