Scopolamine is a naturally occurring compound, known as a tropane alkaloid, found in various plants. This substance has a long history of use due to its potent effects on the human body. It possesses a dual nature, acting as both a valuable medicinal agent when used under controlled conditions and a dangerous substance capable of causing severe harm when misused. Scopolamine’s pharmacological properties have made it a subject of extensive study and careful application in modern medicine.
Plants Containing Scopolamine
Scopolamine is primarily found in plants belonging to the Solanaceae family, commonly known as nightshades. Key examples include Datura species, often called Jimsonweed or Devil’s Trumpets, which are herbaceous annuals or short-lived perennials reaching up to 2 meters tall. Datura plants feature large, trumpet-shaped flowers, typically white to pale purple, and distinctive spiny fruit capsules. All parts of the plant are highly toxic.
Another source is Brugmansia, known as Angel’s Trumpets, which are woody shrubs or small trees with large, pendulous, trumpet-shaped flowers. These plants are native to tropical regions of South America but are cultivated worldwide and can grow up to 3 to 11 meters tall. Their flowers are fragrant at night.
Atropa belladonna, or Deadly Nightshade, is also a member of this family and a source of scopolamine. This perennial herbaceous plant typically grows up to 1.5 meters tall and has dull purple, bell-shaped flowers that mature into shiny black berries. Native to Europe and Western Asia, belladonna is extremely toxic, with all parts of the plant containing potent alkaloids. The concentration of scopolamine and other alkaloids can vary significantly among these plants, making their effects unpredictable and dangerous outside of controlled environments.
How Scopolamine Interacts with the Body
Scopolamine exerts its effects by acting as an anticholinergic drug, meaning it blocks the action of a neurotransmitter called acetylcholine. Acetylcholine plays a broad role in transmitting signals between nerve cells throughout the nervous system, including regions that regulate involuntary actions like digestion and heart rate, as well as parts of the brain involved in cognitive functions. Scopolamine specifically targets muscarinic acetylcholine receptors, which are found in various parts of the body, including the brain, heart, smooth muscles, and glands.
When scopolamine binds to these receptors, it acts as a competitive antagonist, preventing acetylcholine from activating its receptor. This blocking action reduces the activity of the parasympathetic nervous system. This interference with normal cholinergic signaling forms the basis of scopolamine’s diverse effects. For example, its action in the brain’s vestibular system and vomiting center helps prevent nausea.
In other parts of the body, scopolamine’s anticholinergic effects lead to reduced secretions from glands, such as saliva, causing dry mouth. It can also affect the smooth muscles of the gastrointestinal and urinary tracts, leading to relaxation and reduced motility. Scopolamine influences the central nervous system, which can result in effects like drowsiness, blurred vision due to altered eye muscle control, and changes in cognitive function.
Therapeutic Applications of Scopolamine
Despite its potent nature, scopolamine has medical applications. One of its primary uses is in the prevention of motion sickness, where it is often administered via a transdermal patch placed behind the ear. This patch provides a continuous, controlled release of the medication over several days, effectively reducing nausea and vomiting.
Scopolamine is used to prevent post-operative nausea and vomiting (PONV) associated with anesthesia or opiate analgesia. A patch is typically applied the evening before surgery and left in place for 24 hours. This helps to calm the muscles in the stomach and bowels, contributing to patient comfort during recovery.
In pre-anesthetic medication, scopolamine can be used to decrease secretions in the respiratory tract, which is beneficial during surgical procedures. This action helps to reduce the risk of complications related to excessive saliva or bronchial secretions. In end-of-life care, scopolamine is sometimes used to reduce noisy respiratory secretions, often referred to as “death rattle,” to improve patient comfort. While effective, its use in this context may be limited by its potential for central nervous system side effects and delayed onset of action when administered via patch.
Potential Hazards and Misuse
The unsupervised use or misuse of scopolamine, particularly from plant sources, carries hazards due to its extreme toxicity and unpredictable potency. Even small doses can lead to severe poisoning. Common side effects can include dry mouth, blurred vision, dilated pupils, drowsiness, and dizziness. More severe reactions include disorientation, confusion, agitation, and hallucinations.
Overdose symptoms can escalate to lethargy, somnolence, coma, convulsions, and visual disturbances like seeing halos around lights. The unpredictable concentration of alkaloids in wild plants makes recreational use dangerous, leading to severe delirium and a lack of motor control. Users or victims may enter a “zombie-like” state, lacking free will and experiencing memory loss, which has led to its association with criminal activities such as robberies.
Beyond acute poisoning, scopolamine can also cause hyperthermia (high body temperature), particularly in children and older adults, which can lead to complications and even death. Withdrawal symptoms, such as dizziness, nausea, headaches, and neuropsychiatric manifestations, can occur after discontinuing use, especially if used continuously. Due to these effects, medical supervision is necessary for any use of scopolamine, and self-administration from plant sources poses a risk to health and safety.