Atropa belladonna is more commonly known simply as belladonna, or as deadly nightshade. It is a herbaceous plant, native to Europe, and it contains several highly toxic tropane alkaloids.
Despite its deadly reputation, however, belladonna has been used for medicinal purposes for hundreds of years. During the middle ages, it was used as an anaesthetic for surgery, and its name comes from its use as eye drops for Italian women, which dilated the pupils and were believed to enhance beauty.
Belladonna contains atropine and scopolamine, which regulate the heart rate and relax muscle spasms. It is thought to be helpful for the relief of irritable bowel syndrome, and it has been studied for its contribution towards the treatment of Parkinson's disease.
Belladonna is widely available as a homeopathic remedy; due to the way homeopathic remedies are prepared and diluted, only a handful of the original molecules will remain in the resulting remedy. Belladonna tablets can be taken for a wide variety of ailments, ranging from stomach upsets to aching joints, anxiety and menopausal symptoms such as hot flushes.
You can also buy belladonna plasters, designed to attach to the skin over aching and sore muscles, and to provide some pain relief.