Potassium bromide (KBr) is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries, with over-the-counter use extending to 1975 in the US.

[citation needed] Potassium bromide, a typical ionic salt, is fully dissociated and near pH 7 in aqueous solution.

[6] Locock noted that bromide calmed sexual excitement and thought this was responsible for his success in treating seizures.

In the latter half of the 19th century, potassium bromide was used for the calming of seizure and nervous disorders on an enormous scale, with the use by single hospitals being as much as several tons a year (the dose for a given person being a few grams per day).

The British Army has historically been claimed to lace soldiers' tea with bromide to quell sexual arousal and in the Victorian era prisoners in England were compulsorily dosed with the chemical.

As with other antiepileptics, sometimes even therapeutic doses (3 to 5 grams per day, taking 6 to 8 weeks to reach stable levels) may give rise to intoxication.

Often indistinguishable from 'expected' side-effects, these include: Potassium bromide is transparent from the near ultraviolet to long-wave infrared wavelengths (0.25-25 μm) and has no significant optical absorption lines in its high transmission region.

Alternatively, samples may be analyzed as a liquid film (neat, as a solution, or in a mull with Nujol) between two polished potassium bromide discs.