What is Sodium Channel Blocker Toxicity?
Medications that block sodium channels have a wide range of uses. They include drugs to manage heart rhythm issues, local anesthetics that numb areas of the body, and many medicines used to treat nerve pain. These include certain types of antidepressants (TCA), anticonvulsant medications, and even cocaine. Some specific examples are quinidine and procainamide (used for heart rhythm issues), lidocaine and mexiletine (local anesthetics), and carbamazepine and lamotrigine (for nerve pain).
It’s important to note that some heart medications, like propranolol and acebutolol, can also block sodium channels. As well, some insecticides are known to have properties that interact with sodium channels. This can be very serious, as too much of these substances, either on purpose or by accident, can cause dangerous effects including risk of death. Therefore, it is crucial to understand how to safely use these medications and manage any toxicity or side effects that may occur.
What Causes Sodium Channel Blocker Toxicity?
Poisoning from sodium channel-blocking medications typically comes from taking too much on purpose. However, there are cases where a patient or their family member may report accidentally taking too much of their medication or starting a new medicine that changes how the body removes the substance from the system, leading to an unexpected harmful dose. Sometimes, too much of this type of medicine can be given by mistake during medical care, like when large amounts of local anesthesia are used during a procedure. This is called an iatrogenic overdose.
Risk Factors and Frequency for Sodium Channel Blocker Toxicity
Intentional poisonings often involve swallowing more than one type of drug. The instances of harm from sodium channel blockers (a type of drug) can vary based on the specific drug taken. Some numbers from the 2021 report of the American Association of Poison Centers can shed some light on this:
- Antihistamines: 14,595 cases were reported, with 101 ending in death.
- Beta-adrenergic receptor antagonists: 27,541 cases reported, and 18 deaths.
- Local or topical anesthetics: 5,471 cases reported.
- Tricyclic antidepressants: 7,781 cases reported (making up 5.6% of all reported drug-related incidents), with 42 deaths.
- Carbamazepine or oxcarbazepine: 6,755 cases reported.
- Phenytoin or fosphenytoin: 1,374 cases.
- Lamotrigine: 10,863 cases.
Other studies show that around 78.7% of people who overdose on TCAs (a type of antidepressant) end up in the hospital, and 0.73% die as a result. Reports also suggest that harm from local anesthetics is generally rare, with rates between 0.02% and 0.18%.
Signs and Symptoms of Sodium Channel Blocker Toxicity
People who have been exposed to excess sodium channel blocker drugs will typically tell their doctors about an accidental or intentional overdose, or a mistaken medication dose given by healthcare professionals. It’s important for doctors to know about every single drug someone has taken if they are suspected of overdose. Often, people may have taken additional over-the-counter medications like acetaminophen or aspirin, or used other substances such as alcohol, cocaine, or opioids. It can be helpful to look at a person’s medication list, their electronic medical record, or get in touch with their pharmacy to gather more information.
Doctors will conduct a detailed physical examination. This exam can help identify signs that suggest a specific type of poisoning (like anticholinergic syndrome) and determine the severity. The exam will include checking the patient’s:
- Mental state
- Pupil size
- Presence of sweating
- Lack of sweat in the armpit, which doctors call the “toxicologist handshake”
- Lack of intestinal sounds
- Muscle stiffness
- Redness of the skin
- Tremors
Patients who have taken too much of drugs like certain antidepressants (TCAs) or antihistamines might seem tired, confused, or even irritated. They usually have fast heartbeats and other signs of anticholinergic poisoning, including dilated pupils, decreased sweat production, and fever. Those who have cocaine poisoning usually seem agitated and show signs of increased adrenaline activity, such as a rapid heartbeat, sweating, high blood pressure, and chest pain.
Individuals who have been given too much of a local anesthetic drug by healthcare professionals typically show symptoms rapidly after getting the drug. They may start by feeling numbness or tingling around their mouth, then evolve to feel dizzy, mentally altered, or could even fall into a coma, have seizures, or experience cardiac or respiratory arrest due to irregular heart rhythms. More powerful local anesthetics, like bupivacaine, may cause heart problems without the preceding nervous system issues.
Testing for Sodium Channel Blocker Toxicity
If there is a concern that someone has consumed a medication that blocks sodium channels, it’s important to note that there are no specific symptoms or conditions that always occur with this type of poisoning. The symptoms people experience can vary depending on the specific medication taken. For instance, people who have swallowed tricyclic antidepressants (TCAs), a type of medication often used for depression, panic disorder, and certain types of pain, may experience a rapid heartbeat. On the other hand, those who have consumed pure medications that block sodium channels can have a significantly slow heartbeat.
If sodium channel blocker poisoning is suspected, an immediate electrocardiogram (ECG), a test that checks the heart’s electrical activity, should be done. The test might show changes in the ECG pattern including, a widening of the QRS complex (part of the ECG wave that signifies electrical activity of the heart), lengthening of the QT interval (another part of the ECG wave) a change towards the right in the axis of the heart’s electrical activity, irregular slower heartbeats, or even more dangerous heart rhythms such as ventricular tachycardia (fast and erratic heartbeat), ventricular fibrillation (erratic electrical impulses that cause the heart to quiver), and torsades des pointes (a fast form of heart arrhythmia). There can also be signs of a condition called Brugada phenocopy, a disorder that affects the heart’s electrical activity.
In addition to the ECG, other tests such as checking the blood for electrolyte (minerals in your blood and fluid such as sodium, potassium, and calcium), kidney, and liver function, checking for acetaminophen (a common over-the-counter painkiller) and salicylate (the active ingredient in aspirin) levels, assessing gases in the blood, screening for drugs, and a complete blood count (a test that measures different cells in the blood) might also be needed. These tests will help determine if any other substances have been consumed.
Treatment Options for Sodium Channel Blocker Toxicity
When a patient in a critical condition comes in, the immediate first step is to check the patient’s ability to breathe, circulation, and consciousness. In some cases, the patient may have low blood pressure, slow or rapid heartbeat, or a change in mental state. When a patient cannot protect their airway (the passage through which air reaches the lungs), doctors may need to insert an advanced breathing tube. This might also happen if the patient’s breathing becomes too weak or if they go into cardiac arrest.
If someone has consumed harmful substances in large amounts, activated charcoal could be used early in their treatment. Activated charcoal can absorb these substances and help prevent them from harming the body further. However, this treatment must be considered carefully, especially for patients who might not be fully conscious or are vomiting. These patients are more likely to accidentally inhale or swallow the charcoal into their lungs, which can cause further complications.
For patients experiencing toxicity due to sodium channel blockers (medications affecting how sodium ions move in and out of cells), sodium bicarbonate is extremely important to their treatment. If a patient’s heart rhythm is visibly abnormal, this means they need sodium bicarbonate. It works by increasing the pH and sodium levels in the blood, which helps restore the balance across the cell membranes. This might also help promote the binding of the harmful substance to proteins in the blood, which can neutralize its effects.
In some cases, when a patient remains unstable despite all initial treatments, hypertonic saline might be used. This is a solution with higher sodium content, which can help correct the sodium levels in the patient’s body. Lidocaine, a medication that can help regulate heart rhythms, may also be employed.
If the patient’s blood pressure remains low, a combination of treatments can be used to manage it, including fluids and medications that constrict blood vessels and increase heart muscle contractions. Norepinephrine is a common medication used in these situations. More medications, such as epinephrine or vasopressin, can be added as needed. Some severe cases have been treated with a lipid emulsion. This is thought to work by acting as a sort of sponge to soak up the harmful substances.
If patients develop seizures, they would be managed with medications like lorazepam and midazolam, not phenytoin as it might worsen the condition. If seizures continue, the patient might need to be intubated, sedated, and considered for an advanced life support tool called ECMO (adjunctive method to provide both cardiac and respiratory support).
What else can Sodium Channel Blocker Toxicity be?
People may experience heart rhythm problems, known as ventricular dysrhythmias, due to several reasons like:
- Acute coronary syndrome (a serious heart condition)
- Abnormal levels of elements in the body (like low magnesium or high potassium)
- Born with heart disease (congenital cardiac disease)
- Heart diseases that cause changes to its structure
Also, some medicines may cause a specific kind of toxic reaction that affects the sodium channels in the body. These medicines might include:
- Antihistamines (medicines often used for allergies)
- Antipsychotics (medicines used for conditions like schizophrenia or bipolar disorder)
- Antispasmodics (medicines used to control muscle spasms)
- Chloroquine (a medicine often used for malaria)
- Class Ia and Ic antiarrhythmics (types of heart medicines)
- Cocaine (illegal drug)
- Local Anesthetics (medicines that cause a loss of sensation)
- Phenothiazines (a group of medicines primarily used for mental health disorders)
- Venlafaxine toxicity (a reaction to an antidepressant medicine called venlafaxine)
What to expect with Sodium Channel Blocker Toxicity
An overdose of an antidepressant medication called TCA is known to have a high death rate. Specifically, side effects from class I antiarrhythmics, which are drugs that regulate heart rhythm, can lead to a higher death rate of 22.5% compared to other drugs (1%).
It’s very important to recognize and treat this quickly to reduce harm or risk of death. If sodium channel blocker toxicity – a harmful side effect caused by certain medications that affect heart rhythms – is identified early and treated appropriately, full recovery is achievable.
Possible Complications When Diagnosed with Sodium Channel Blocker Toxicity
Complications from sodium channel blocker toxicity can range from mild to severe. Possible complications include:
- Low blood pressure (hypotension)
- Slow heart rate (bradycardia) or fast heart rate (tachycardia)
- Cardiogenic shock, a condition where the heart can’t pump enough blood to meet the body’s needs
- Cardiovascular collapse, a sudden and complete failure of the heart to function
- Respiratory depression, a slow and ineffective breathing pattern
- Encephalopathy, a broad term for any brain disease that alters brain function or structure
- Status epilepticus, a dangerous condition in which epileptic seizures follow one another without recovery of consciousness in between
- Death
Preventing Sodium Channel Blocker Toxicity
When local anesthetics are used, the medical team should be aware of the maximum safe dosage to prevent harmful effects. During the process, it’s important to avoid accidentally injecting the drug into a blood vein or artery. This can be done by drawing back the plunger of the syringe before injecting to make sure no blood is present.
Some local anesthetics like lidocaine and bupivacaine can have epinephrine added to them. The purpose of this addition is to help increase the safe dose by slowing down the spread of the drug in the body. This is due to epinephrine’s function of narrowing blood vessels.
Sodium channel blocker toxicity is a medical term for a harmful reaction caused by exposure to certain medications. The best way to deal with this is to prevent it from happening in the first place, by carefully managing medicine dosages. Also, some medicines, like TCAs or tricyclic antidepressants, can also cause harmful effects if accidentally taken in large amounts.
Patients who have a mental health condition that puts them at risk of harming themselves, or who may have trouble managing their medications properly, should ensure they take precautions when dealing with these kinds of drugs. This might involve using pill dispensers or having a family member or caregiver help manage their medications.