A seizure is an electrical event. Epilepsy is the tendency for the brain to have them.

The brain runs on electrical signals. Neurons communicate by generating brief electrical impulses — action potentials — that travel along axons and cross synapses to the next cell. In a healthy brain, this activity is tightly regulated by two opposing forces: excitatory neurotransmitters (primarily glutamate) that push neurons toward firing, and inhibitory neurotransmitters (primarily GABA) that hold them back.

A seizure occurs when this balance tips sharply toward excitation in a group of neurons. They fire in an abnormally synchronized, high-frequency rhythm, and the synchronized discharge spreads — either staying in one region (focal seizure) or involving both hemispheres at once (generalized seizure). The behavioral result depends on where in the brain the discharge begins and how far it spreads.

Epilepsy is not defined by a single seizure. It is diagnosed when a person has had at least two unprovoked seizures more than 24 hours apart, or one unprovoked seizure with a high risk of recurrence (such as an abnormal EEG or an identifiable structural lesion). Many people who have one seizure never have another, and they do not have epilepsy.

Epilepsy has many causes. In children, genetic factors dominate — many epilepsy syndromes are inherited or arise from de novo mutations in genes governing ion channels or synaptic proteins. In adults, structural causes become more common: stroke, traumatic brain injury, brain tumors, prior infection, or hippocampal sclerosis. In about half of all cases, no specific cause is identified despite extensive workup.

The practical consequence of this biology is that anti-seizure medications work by shifting the excitatory-inhibitory balance — usually by blocking sodium or calcium channels (reducing excitation), enhancing GABA signaling (increasing inhibition), or modulating synaptic vesicle release. Different mechanisms target different seizure types, which is why the choice of medication depends on getting the classification right.

Why the classification matters for treatment: some medications that work well for focal seizures can worsen generalized seizures — and vice versa. Carbamazepine, oxcarbazepine, phenytoin, and gabapentin are effective for focal seizures but can aggravate absence, myoclonic, and atonic seizures. Ethosuximide is specific for absence seizures and useless for focal seizures. Valproate and lamotrigine have broad-spectrum activity but carry their own risks. Getting the type right is not academic — it is the difference between a working prescription and one that makes the seizures worse.

Two practical principles that matter more than the specific drug: First, choose the medication matched to the seizure type, not just to "epilepsy." A focal-specific drug for a generalized epilepsy can make the seizures worse. Second, monotherapy at the optimal dose usually beats combination at low doses — but if the first drug fails, switching to another single drug is often better than adding a second one. About 70% of patients become seizure-free with this approach.

Never stop anti-seizure medication abruptly. Sudden discontinuation can trigger withdrawal seizures, including status epilepticus — even in patients who have been seizure-free for years. Any change should be gradual and supervised.

Most anti-seizure medications are available as low-cost generics in the United States. Levetiracetam, lamotrigine, carbamazepine, oxcarbazepine, valproate, phenytoin, topiramate, zonisamide, and ethosuximide are all generic and priced well below their original brand versions. Levetiracetam in particular is inexpensive and widely stocked. This is one of the medications where cost is rarely the barrier to treatment — the barrier is usually access to a neurologist.

Newer agents remain brand-only: brivaracetam, perampanel, cenobamate, eslicarbazepine, and fenfluramine are considerably more expensive and typically require prior authorization. Vagus nerve stimulation and epilepsy surgery are covered by most insurance plans when medically indicated, but require referral to a comprehensive epilepsy center.

What still varies at the pharmacy counter: the same generic tablet can cost several times more at one licensed pharmacy than another. For a chronic medication taken for years, that difference compounds. A live prescription price comparison shows the current range in about two minutes, and the same logic applies to every generic on a patient's list. If you are filling an online refill for the first time, the process is documented step by step in this how to order prescriptions online guide — prescription first, licensed seller second, small first order third.

One note specific to epilepsy: do not skip doses or switch manufacturers without telling your neurologist. Anti-seizure medications have a narrow therapeutic window, and small changes in blood levels can trigger breakthrough seizures. If a pharmacy substitutes a different manufacturer, plan to recheck levels or monitor closely for a few weeks.

Before filling from any seller — online or local — verify them. A working VIPPS seal that resolves to a live NABP record, a real U.S. street address, and a prescription requirement that cannot be waived. A transparency page like this one about Metformin4You is a reasonable example of the standard to expect.