Bumetanide, a drug that has been on the market for decades and has been established as safe, was used in a double-blind, placebo-controlled study in 60 autistic children (age range, 3–11). Bumetanide at 1 mg/day or placebo was given for 90 days, followed by a 30-day washout and final ratings (i.e., at day 120).
Throughout the years bumetanide has been used as a diuretic and also as an antiepilepsy medication. The reason it is used to prevent seizures, is that it is believed to act by lowering intracellular chloride levels, which switches gamma-aminobutyric acid from excitatory to inhibitory action. So, it is theorized, that a similar outcome might be true for patients with autism.
Once the trial was completed it was found that those receiving the bumetanide showed significant improvements in their autism symptoms. It also showed pathology decreasing to mild or moderate severity. However, wider research showed that in the most severe autism cases there was little to no change. In fact, patients with evidence of hypokalemia, who were being treated with potassium, were actually worse after the washout.
Lemonnier E et al. A randomised controlled trial of bumetanide in the treatment of autism in children. Transl Psychiatry 2012 Dec 11; 2:e202. (http://dx.doi.org/10.1038/tp.2012.124) Published in Journal Watch Psychiatry December 21, 2012