An overdose, consuming a toxic amount of any substance, can frequently lead to a seizure. A seizure is a sudden, uncontrolled electrical disturbance in the brain, causing changes in behavior, movements, feelings, and consciousness. When a substance is taken in excess, its toxic concentration disrupts the delicate electrochemical balance of the central nervous system. This overwhelming effect on the brain’s natural regulatory systems creates an environment where a seizure is likely to occur.
The Neurochemical Mechanism of Drug-Induced Seizures
The fundamental cause of a seizure is an imbalance between excitation and inhibition within the brain’s neuronal networks. The central nervous system maintains equilibrium between these opposing forces using specific chemical messengers called neurotransmitters. Overdosing immediately tips this balance, leading to the uncontrolled, synchronous firing of neurons that manifests as a seizure.
The primary inhibitory neurotransmitter in the brain is gamma-aminobutyric acid (GABA), which acts like a brake pedal on neuronal activity. GABA works by binding to receptors on the nerve cells, causing an influx of negative ions. This makes the cell less likely to fire an electrical impulse. Conversely, glutamate is the main excitatory neurotransmitter, functioning like an accelerator. Glutamate increases the likelihood of a neuron firing a signal.
Many substances cause seizures by either suppressing GABA’s inhibitory effects or amplifying glutamate’s excitatory effects. Some drugs directly block GABA receptors, effectively removing the brain’s natural braking mechanism. Other substances increase the release or slow the reuptake of excitatory neurotransmitters, flooding the synapses and causing uncontrolled activation.
High concentrations of certain substances can also cause neurotoxicity, which is direct damage or severe irritation to the neuronal tissue itself. This toxicity can lower the seizure threshold, making the brain more susceptible to abnormal electrical discharges.
Pharmaceutical and Illicit Substances That Increase Seizure Risk
A wide variety of substances, both legally prescribed and illicit, increase the risk of a seizure when taken in excess. Stimulants, including cocaine, methamphetamine, and MDMA, flood the brain with excitatory neurotransmitters. This leads to an over-activation of the central nervous system that can provoke a seizure.
Certain prescription medications also pose a significant risk in overdose situations due to their specific effects on neurotransmitter pathways. Antidepressants, particularly tricyclic antidepressants and some selective serotonin reuptake inhibitors (SSRIs), can lower the seizure threshold when taken in high doses. Tramadol, an opioid pain medication, is frequently implicated in drug-induced seizures. The risk increases substantially during misuse or overdose.
Withdrawal Seizures
Withdrawal from central nervous system depressants, such as alcohol and benzodiazepines, is another mechanism for seizure induction. Chronic use of these drugs enhances GABA’s inhibitory effects. Their sudden absence causes a rebound hyperexcitability in the brain, resulting in a withdrawal seizure.
Other medications like bupropion, an antidepressant and smoking cessation aid, are known to cause seizures in overdose. Additionally, over-the-counter antihistamines like diphenhydramine can also be a cause of seizures when consumed in toxic amounts.
Immediate Steps and Emergency Medical Treatment
Witnessing a seizure caused by an overdose requires immediate action focused on safety and securing emergency help. Call emergency medical services immediately, providing the dispatcher with any known information about the substance involved. Stay with the person and time the seizure, noting how long the convulsive activity lasts.
During the seizure, the priority is to protect the person from injury by clearing the area of any hard or sharp objects. Gently ease the person to the ground and place something soft and flat, like a folded jacket, under their head. Do not attempt to restrain the person or place anything in their mouth, as these actions can cause injury to the person’s limbs or dental trauma.
Once the seizure activity stops, gently roll the person onto their side into the recovery position, which helps keep the airway clear, especially if there is fluid or vomit. Seek medical attention if the seizure lasts for five minutes or longer, or if a second seizure occurs shortly after the first. The goal of hospital treatment is to stabilize the patient’s vital signs and terminate the seizure activity.
In the emergency room, the primary treatment for a drug-induced seizure is often the administration of a benzodiazepine, such as lorazepam or midazolam. These medications work by enhancing the inhibitory effects of GABA, quickly restoring the balance between excitation and inhibition in the brain. The specific substance taken will guide further treatment, which may involve supportive care and specific antidotes to manage the underlying overdose toxicity.