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CAS Number 7758-02-3
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Linear Formula KBr
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Molecular Weight 119.00
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EC Number 231-830-3
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MDL number MFCD00011358
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PubChem Substance ID 329752283
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eCl@ss 38050405
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. Its action is due to the bromide ion (sodium bromide is equally effective). Potassium bromide is
used as a veterinary drug, as an antiepileptic medication for dogs.
Detailed
description
Under standard conditions, potassium bromide is
a white crystalline powder. It is freely soluble in water; it is not soluble in
acetonitrile. In a dilute aqueous solution, potassium bromide tastes sweet, at
higher concentrations it tastes bitter, and tastes salty when the concentration
is even higher.[by
how much?] These effects are mainly due to the properties
of the potassium ion—sodium bromide tastes salty at any concentration. In high
concentration, potassium bromide strongly irritates the gastric mucous
membrane, causing nausea and sometimes vomiting (a typical effect of all
soluble potassium salts).
Applications
Medical and veterinary
The anticonvulsant properties of potassium bromide
were first noted by Sir Charles Locock at a meeting of the Royal Medical and
Chirurgical Society in 1857. Bromide can
be regarded as the first effective medication for epilepsy. At the time, it
was commonly thought that epilepsy was caused by masturbation.[3] 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).[3]
There was not a better epilepsy drug until phenobarbital in 1912. It was
often said the British Army laced soldiers' tea with bromide to
quell sexual arousal—but that is likely untrue as doing so would also diminish
alertness in battle and similar stories exist about a number of substances.[4][citation needed]
Bromide compounds, especially sodium bromide, remained in over-the-counter
sedatives and headache remedies (such as the original formulation of Bromo-Seltzer) in the US until
1975, when bromides were outlawed in all over-the-counter medicines, due to
chronic toxicity.[5] Bromide's
exceedingly long half life in the body made it difficult to dose without side
effects (see below). Medical use of bromides in the US was discontinued at this
time, as many better and shorter-acting sedatives were known by then.
Potassium bromide is used in veterinary medicine to
treat epilepsy in dogs, either as
first-line treatment or in addition to phenobarbital, when seizures are not
adequately controlled with phenobarbital alone. Use of bromide in cats is
limited because it carries a substantial risk of causing lung inflammation
(pneumonitis) in them. The use of bromide as a treatment drug for animals means
that veterinary medical diagnostic laboratories are able as a matter of routine
to measure serum levels of bromide on order of a veterinarian, whereas human
medical diagnostic labs in the US do not measure bromide as a routine test.
Potassium bromide is not approved by the US Food and Drug
Administration (FDA) for use in
humans to control seizures. In Germany, it is still approved as an
antiepileptic drug for humans, particularly children and adolescents.[6] These indications
include severe forms of generalized tonic-clonic seizures,
early-childhood-related Grand-Mal-seizures, and also severe myoclonic seizures
during childhood. Adults who have reacted positively to the drug during
childhood/adolescence may continue treatment. Potassium bromide tablets are
sold under the brand name Dibro-Be
mono (Rx-only). The drug has
almost complete bioavailability, but the bromide ion has a relatively long half
life of 12 days in the blood,[3] making bromide salts
difficult to adjust and dose. Bromide is not known to interfere with the
absorption or excretion of any other anticonvulsant, though it does have strong
interactions with chloride in the body, the normal body uptake and excretion of
which strongly influences bromide's excretion.[3]
The therapeutic index (ratio of effectiveness to
toxicity) for bromide is small. 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:
Bromism These are central
nervous system reactions. They may include:
depression,
lethargy, somnolence (from daytime
sleepiness to coma)
loss of reflexes or pathologic
reflexes
loss of neural
sensitivity
cerebral edema with associated
headache and papilledema of the eyes
delirium: confusion,
abnormal speech, loss of concentration and memory, aggressiveness
Acne-form dermatitis and other forms of skin disease
may also be seen, as well as mucous hypersecretion in the lungs. Asthma and
rhinitis may worsen. Rarely, tongue disorder, aphten, bad breath, and
obstipation occur.
Optics
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. It is used widely as infrared optical windows and components for
general spectroscopy because of its wide spectral range. In infrared spectroscopy, samples are analyzed by grinding with powdered potassium
bromide and pressing into a disc. 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.[7]
Due to its high solubility and hygroscopic nature it must be
kept in a dry environment. The refractive index is about 1.55 at
1.0 µm.
Photography
In addition to manufacture of silver bromide,
potassium bromide is used as a restrainer in black and white developer formulas. It
improves differentiation between exposed and unexposed crystals of silver
halide, and thus reduces fog.
PRICE
$1251.68/KG OR $568.94/IB
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