High levels of bromide chronically impair the membrane of neurons, which progressively impairs neuronal transmission, leading to toxicity, known as bromism. Bromide has an elimination half-life of 9 to 12 days, which can lead to excessive accumulation. Doses of 0.5 to 1 gram per day of bromide can lead to bromism. Historically, the therapeutic dose of bromide is about 3 to 5 grams of bromide, thus explaining why chronic toxicity (bromism) was once so common. While significant and sometimes serious disturbances occur to neurologic, psychiatric, dermatological, and gastrointestinal functions, death is rare from bromism.
Bromism is caused by a neurotoxic effect on the brain which results in somnolence, psychosis, seizures and delirium. Bromism has also been caused by excessive soda consumption, due to the presence of brominated vegetable oil, leading to headache, fatigue, ataxia, memory loss, and eventually inability to walk in one case.