Drug-induced metabolic encephalopathy is a complex term that describes a relatively simple to understand medical condition: brain dysfunction due to a severe imbalance in normal body processes caused by drugs or medications. Essentially, it’s a series of changes in thinking, memory, and normal cognitive processes that come about as an adverse effect of drugs.
This article covers the symptoms, diagnosis, treatment, and prevention of drug-induced metabolic encephalopathy.
- Metabolic encephalopathy has a range of causes, including illicit substance use, adverse effects from medications, and complications of chronic diseases.
- Symptoms include reduced awareness, altered thinking and attention, disturbed sleep, abnormal movements, and psychiatric changes.
- Treatment for drug-induced metabolic encephalopathy is usually supportive, with medications being given to address substance overdose or withdrawal when necessary.
What is metabolic encephalopathy?
Metabolic encephalopathy is a term that describes symptoms of abnormal brain function resulting from the presence of a disease, illness, toxin, or other insult to the body's normal functioning. Symptoms can range from mild signs only noticeable to a trained professional, right through to coma and even death. Changes may be acute (lasting only a short time) or result in permanent brain damage. [1]
In short, metabolic encephalopathy describes a broad range of neurological and psychiatric symptoms, with many causes, that can last an undetermined amount of time.
Delirium
Clinicians sometimes refer to metabolic encephalopathy as ‘delirium’ or ‘acute confusional states’. However, these definitions are contentious and not universal. Many practitioners draw a line between delirium (a temporary and fluctuating state of reduced consciousness and thinking ability) and metabolic encephalopathy (involving more severe and widespread brain dysfunction). [2][3]
For the purpose of this article, we will be using the term ‘metabolic encephalopathy’ when describing the effects of substance misuse on normal brain function.
Types of encephalopathy
There are various types of encephalopathy to be aware of. Some of the most important include: [4][5]
Reversible encephalopathies
- Toxic metabolic encephalopathy: The buildup of toxins in the body.
- Acute metabolic encephalopathy: A lack of essential substances such as glucose, oxygen, or key vitamins.
- Hepatic encephalopathy: High levels of ammonia as a result of liver failure.
- Wernicke’s encephalopathy: Vitamin B1 (thiamine) deficiency from long-term alcohol misuse or malnutrition.
- Uremic encephalopathy: The buildup of urea due to kidney failure.
- Hypertensive encephalopathy: Severe high blood pressure causing brain swelling.
Irreversible encephalopathies
- Chronic traumatic encephalopathy: From repeated physical injury to the head and brain.
- Hypoxic ischemic encephalopathy: Lack of oxygen to brain tissues (such as during cardiac arrest).
- Hashimoto’s encephalopathy: The exact cause is unknown, but it is likely due to an abnormal autoimmune response.
These definitions aim to provide a general understanding of the types of conditions that can lead to encephalopathy. In reality, causes and clinical presentations often overlap and may not be as distinct as this list implies.
Substance use and toxic metabolic encephalopathy
Substance misuse can lead to widespread physical and psychological health issues, including encephalopathy. Substances have the potential to lead to encephalopathy in two ways: [6]
- Hypoxic ischaemic: During an overdose, drugs can slow or stop your ability to breathe. Oxygen starvation can quickly lead to permanent brain damage.
- Toxic metabolic: The toxic substances present in illicit substances, as well as unwanted, harmful byproducts produced in the body, can cause significant harm to the brain.
Unfortunately, there is limited information available about which substances are associated with the greatest risk of toxic metabolic encephalopathy, with many clinical studies relying on information from physician case reports. Substances with the potential to cause encephalopathy include: [6][7][8][9]
- Alcohol
- Cocaine
- Heroin
- Morphine
- Oxycodone
- Methadone
- Fentanyl
- Stimulants (including methamphetamine)
Alcohol and Wernicke's encephalopathy
Long-term alcohol misuse can lead to a specific form of brain injury called Wernicke’s encephalopathy. People who chronically misuse alcohol are unable to properly absorb and process thiamine, a vitamin essential for several vital processes in the brain. [10]
Clinicians recognize Wernicke’s encephalopathy from a triad of symptoms: nystagmus (abnormal involuntary movements of the eyes), ataxia (poor muscle control and clumsy movements), and confusion. This condition is potentially life-threatening and requires rapid correction with a thiamine infusion. [10]
Symptoms of metabolic encephalopathy
The symptoms of metabolic encephalopathy are wide-ranging. Toxins can cause damage to any and all regions of the brain, resulting in many unique neurological and psychiatric symptoms. Common symptoms of metabolic encephalopathy include:
- Altered consciousness: One of the most widely recognized symptoms of metabolic encephalopathy is a reduced level of consciousness and activity. The level of awareness can fluctuate between a light daze and being completely unable to wake up. [11]
- Changes in thinking and attention: People with metabolic encephalopathy often demonstrate a pattern of disorganized thinking. This may include memory issues, being unoriented to time and place, and being unable to process language properly. They are also likely to have a reduced attention span, making it difficult for them to follow conversations and keep up with events around them. [11]
- Disturbed sleep: The normal sleep-wake cycle is usually disrupted in people with metabolic encephalopathy. Sleep may be erratic, not following a regular schedule, and last for much longer than usual. [11]
- Movement symptoms: Any insults or injuries to the brain can cause abnormal movements in the rest of the body. Common movement symptoms include asterixis (a flapping tremor indicating an inability to maintain sustained muscle tension) and myoclonus (a quick jerking movement, commonly experienced when falling asleep but abnormal if occurring constantly). [2]
- Psychological symptoms: People with metabolic encephalopathy can experience a range of psychological symptoms, including disturbances in perception, delusions (an unshakable belief about something that is not true), mood changes, and emotional lability. [11]
Is it fatal?
Metabolic encephalopathy refers to the effects of toxins and other insults on the normal functioning of the brain. Unless the root cause is promptly identified and treated, functioning and overall health can continue to decline. In severe cases, the causes of metabolic encephalopathy can lead to permanent damage, disability, and even death. [11]
Causes and prevention
The best way to prevent substance-induced toxic metabolic encephalopathy is to avoid using harmful illicit substances wherever possible. However, it’s essential to recognize that there are many other causes of metabolic encephalopathy outside of substance use: [12]
- Medications, including certain antibiotics, strong pain relief, sedatives, psychiatric agents, and anti-seizure medication
- Organ dysfunction, such as liver or kidney failure
- Malnutrition, causing vitamin deficiencies
- Infection
- Severely high blood pressure
- Chronic health conditions like heart disease and chronic obstructive pulmonary disease (COPD)
- Key electrolyte and hormone imbalances
- Environmental poisons
While many of these causes are difficult to prevent, prioritizing prompt recognition and treatment can reduce the likelihood of long-term brain damage.
Diagnosing metabolic encephalopathy
The diagnosis of metabolic encephalopathy is a complex process. Physicians require a detailed history, examination, laboratory investigations, and clinical imaging to look for contributing factors, as well as to rule out other causes of neurological symptoms (for example, a stroke or brain tumour). [11]
Ultimately, the diagnosis of metabolic encephalopathy is ‘clinical,’ meaning that it is based on recognizing key symptoms and investigation findings as part of a comprehensive assessment of an individual’s overall health. [11]
Treatment options
The mainstay of metabolic encephalopathy treatment is the recognition and removal of contributing causes whenever possible. There is no specific medication or intervention that can be given to reverse the symptoms of this condition. [11] Supportive measures, such as optimizing orientation to time and place, prioritizing high-quality sleep, ensuring adequate fluid intake, and promoting safe mobilization, can all help improve the symptoms of metabolic encephalopathy. [11]
Medications for metabolic encephalopathy
In some cases, medications may be necessary as part of the treatment of the underlying causes of metabolic encephalopathy. In substance-induced toxic metabolic encephalopathy, medications are often needed to either: [11][13]
- Reverse the effect of drugs - for example, naloxone is given to reverse the effect of opioid drugs.
- Provide supportive treatment during an overdose - activated charcoal is commonly used to limit the absorption of a range of poisons.
- Treat withdrawal - benzodiazepines are often given to manage the effects of alcohol withdrawal.
In limited circumstances, where a person’s symptoms present a risk to themselves or others, sedative or antipsychotic medications may be given. [11]
Final thoughts
Drug-induced metabolic encephalopathy is a highly impactful condition that can lead to a wide range of distressing symptoms. Without prompt recognition and professional intervention, damage to the brain can result in permanent disability or even death.
Stay safe by avoiding harmful substances wherever possible and seeking help as soon as the symptoms of metabolic encephalopathy appear.
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