The belladonna flower has a name that means “beautiful lady” in Italian. However, its other common name has a completely different meaning – the deadly nightshade. Both names can be explained by the uses of the flower throughout history. The deadly nightshade (Atropa belladonna) is a small shrub with purple bell-shaped flowers and shiny black berries. All parts of the plant contain various toxins such as atropine, scopolamine and hyoscyamine. These alkaloid toxins are included in a group of chemicals called anticholinergics, because they act on cholinergic receptors on neurons, which are involved in activating the parasympathetic nervous system. As cholinergic receptors are widely utilised throughout the body, anticholinergic toxicity causes a wide range of symptoms.
The main symptoms of anticholinergic toxicity are best remembered using the following mnemonic:
- Hot as a hare (increased temperature – reduced temperature regulation)
- Blind as a bat (blurred vision – dilated pupils)
- Dry as a bone (dry skin, eyes and mouth – decreased secretions)
- Red as a beet (flushing – dilation of blood vessels)
- Mad as a hatter (hallucinations and agitation – neurological interaction)
The name deadly nightshade is obvious as severe toxicity leads to seizures, coma and death. The reason why the deadly nightshade is also called belladonna is that the diluted extract from the plant was used as an eye drop to dilate women’s pupils – a look considered beautiful then (nowadays the effect is used to examine the eye). The toxins extracted are used in other fields of medicine too. Although not used now, anticholinergics were used as an anaesthetic for surgery due to its neuropsychiatric effects. However, atropine is still used in the emergency setting to reverse bradycardia (excessively slow heart rate), as anticholinergics speed up the heart rate. This highlights the fundamental principle of medicine that “the dose makes the poison”. For the only difference between medicine and poison is the dose… and intent (Oscar G. Hernandez, MD).