Pharmacology - ANTIEPILEPTIC DRUGS (MADE EASY)

Summary

This lecture delves into antiepileptic drugs' role in managing epilepsy by balancing neuronal excitability. It explains seizures as electrical surges in the brain due to an imbalance between excitatory and inhibitory processes. The video outlines how drugs like Carbamazepine, Lamotrigine, and Valproic acid target sodium and calcium channels, or enhance GABA activity, to prevent seizures. It also touches on side effects, such as sedation, cognitive issues, and liver toxicity.

Takeaways

• 💊 The primary use of antiepileptic drugs is to prevent or control epilepsy by managing seizures.
• ⚡ Seizures are caused by a sudden burst of uncontrolled electrical activity in the brain due to hyperactive neurons.
• 🧠 Seizures are classified into two types: focal seizures (affecting a portion of the brain) and generalized seizures (affecting both hemispheres, leading to loss of consciousness).
• 🔄 Seizures result from an imbalance between excitatory (glutamate) and inhibitory (GABA) processes in the brain.
• 🔋 Antiepileptic drugs target the balance of excitatory and inhibitory signals by blocking sodium and calcium channels to prevent excessive neuronal firing.
• 🧪 Drugs like Carbamazepine, Oxcarbazepine, Lamotrigine, Phenytoin, Topiramate, Valproic acid, and Zonisamide reduce sodium influx, lowering excitability.
• 🧬 Lamotrigine, Topiramate, Valproic acid, and Zonisamide also inhibit calcium channels, while Gabapentin and Pregabalin target high-voltage calcium channels to modulate neurotransmitter release.
• ⚖️ GABA-targeting drugs like Benzodiazepines, Barbiturates, Tiagabine, and Vigabatrin enhance inhibitory effects by increasing GABA activity in the brain.
• 🚨 Side effects include sedation, dizziness, hyponatremia, visual field loss (Vigabatrin), and weight changes (Valproic acid, Gabapentin).
• ⚠️ Certain drugs pose risks like liver toxicity (Valproic acid, Felbamate) and aplastic anemia (Felbamate).

Q & A

What is the primary use of antiepileptic drugs?

The primary use of antiepileptic drugs is to prevent or control epilepsy, which is commonly known as seizures.

How are seizures classified based on their onset in the brain?

Seizures are classified into two major groups: focal seizures, which affect only a portion of the brain, and generalized seizures, which affect both sides of the brain and almost always cause a loss of consciousness.

What is the underlying cause of seizures according to the lecture?

Seizures can result from an imbalance between inhibitory and excitatory processes in the brain, producing either too little inhibition or too much excitation.

How do neurons communicate with each other?

Neurons communicate through a traveling wave of electrical excitation known as an action potential, which is orchestrated by the opening and closing of ion channels.

What happens when voltage-gated sodium channels open during an action potential?

When voltage-gated sodium channels open, positively charged sodium ions rush into the neuron, reversing the membrane's polarization and triggering further processes, such as the release of neurotransmitters.

What role does glutamate play in neuronal excitation?

Glutamate is an excitatory neurotransmitter that, when released into the synaptic cleft, binds to AMPA and NMDA receptors on the postsynaptic neuron, allowing the entry of sodium and calcium ions, which contribute to further depolarization and excitation.

How do inhibitory neurons help prevent seizures?

Inhibitory neurons release the neurotransmitter GABA, which binds to GABA-A receptors and allows negatively charged chloride ions to enter the neuron. This inhibits further excitation and helps prevent hyperexcitability, which can lead to seizures.

What is the goal of antiepileptic drug therapy?

The goal of antiepileptic drug therapy is to lower neuronal excitability and/or enhance neuronal inhibition to prevent excessive firing of action potentials in neurons.

Which antiepileptic drugs act by blocking voltage-gated sodium channels?

Antiepileptic drugs that block voltage-gated sodium channels include Carbamazepine, Oxcarbazepine, Lamotrigine, Phenytoin, Topiramate, Valproic acid, and Zonisamide.

How do Gabapentin and Pregabalin differ from other calcium channel blockers in their mechanism of action?

Gabapentin and Pregabalin bind to an accessory subunit of the high-voltage-activated calcium channel called alpha-2-delta-1, which modulates the release of excitatory neurotransmitters like glutamate. This is believed to be a key reason for their antiepileptic effects.