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Study Guide: Antiepileptic Drugs (AEDs) in Canada

Overview of AEDs



Definition: Antiepileptic drugs (AEDs) are medications used to manage seizures associated with epilepsy and other neurological disorders. These drugs serve to stabilize neuronal activity and prevent the onset of seizures.Regulation: In Canada, the use and distribution of AEDs are regulated by Health Canada, ensuring that only approved medications are available for prescribing and use.Usage: The selection of AEDs is based on various factors including the type of seizures experienced, individual patient factors (such as comorbid conditions and age), and the specific side effects of the medications. Moreover, AEDs are also used beyond epilepsy for purposes such as migraine prevention, management of neuropathic pain, and stabilization of mood conditions like bipolar disorder.

Classification of Antiepileptic Drugs

AEDs are categorized into three primary generations:

  • First-Generation (Older) AEDs

  • Second-Generation (Newer) AEDs

  • Third-Generation AEDs

A. First-Generation AEDs

  • Phenytoin (Dilantin): Primarily used for generalized tonic-clonic seizures and focal seizures. It works as a sodium channel blocker, stabilizing neuronal membranes.

  • Carbamazepine (Tegretol): Effective for focal seizures and generalized seizures, but not effective for absence seizures. It is also indicated for the treatment of trigeminal neuralgia and bipolar disorder.

  • Valproic Acid (Depakene, Epival): A broad-spectrum AED that is effective against a variety of seizure types, including absence seizures; it is also used in managing mood disorders.

  • Phenobarbital: An older AED that is now rarely used due to its sedative effects and potential for dependence; still important in some acute seizure situations.

  • Ethosuximide (Zarontin): Specifically indicated for absence seizures and works by reducing calcium currents in thalamic neurons.

B. Second-Generation AEDs

  • Lamotrigine (Lamictal): Effective in treating focal and generalized seizures; it is often preferred during pregnancy due to a favorable safety profile compared to other AEDs.

  • Levetiracetam (Keppra): Known for its favorable tolerability profile and minimal drug interactions, it’s often used as adjunctive therapy.

  • Topiramate (Topamax): Besides its use in epilepsy, it is also utilized in preventing migraines and for weight loss; it has multiple mechanisms of action.

  • Gabapentin (Neurontin): Primarily used for focal seizures and managing neuropathic pain; it has a good safety profile.

  • Pregabalin (Lyrica): More potent than gabapentin and indicated for neuropathic pain and fibromyalgia apart from seizures.

C. Third-Generation AEDs

  • Lacosamide (Vimpat): Indicated for focal seizures, it has a unique mechanism of action and fewer drug interactions.

  • Brivaracetam (Briviact): A newer AED that acts similarly to levetiracetam but is more selective, resulting in a lower incidence of side effects.

  • Perampanel (Fycompa): Used for focal and generalized seizures; caution is warranted due to potential psychiatric side effects such as aggression and mood changes.

Mechanism of Action

  • Sodium Channel Blockers: Include Phenytoin, Carbamazepine, Lamotrigine, and Lacosamide; they work by inhibiting the sodium channels that are responsible for depolarization of neurons.

  • Calcium Channel Modulators: Ethosuximide, Gabapentin, and Pregabalin act by inhibiting calcium influx, which is crucial for neurotransmitter release.

  • GABAergic Enhancement: Benzodiazepines, Phenobarbital, and Valproic Acid enhance the effects of GABA, a neurotransmitter that inhibits neuronal firing.

  • Glutamate Receptor Inhibitors: Perampanel blocks glutamate receptors to reduce excitatory neurotransmission.

Common Side Effects and Considerations

Phenytoin (Dilantin)

  • Side Effects: Gingival hyperplasia, hirsutism, dizziness, ataxia, osteoporosis, and teratogenicity in pregnancy.

  • Considerations: Crucial to monitor blood levels and watch for signs of toxicity.

Carbamazepine (Tegretol)

  • Side Effects: Dizziness, drowsiness, hyponatremia, and increased risk of Stevens-Johnson Syndrome.

  • Considerations: Requires monitoring of sodium levels and should be avoided in absence seizures.

Valproic Acid (Depakene, Epival)

  • Side Effects: Weight gain, tremors, fatigue, liver toxicity, and hair thinning.

  • Considerations: High risk for teratogenic effects; liver function tests should be monitored regularly.

Phenobarbital

  • Side Effects: Sedation, cognitive impairment, and mood changes.

  • Considerations: It is a controlled substance with the potential for dependence; monitor for abuse potential.

Ethosuximide (Zarontin)

  • Side Effects: Nausea, vomiting, dizziness, and rare but serious blood disorders.

  • Considerations: Primarily indicated for absence seizures; monitoring should focus on blood counts.

Treatment of Status Epilepticus in Canada

First-Line Treatment: Use of benzodiazepines such as IV Lorazepam, Diazepam, or Midazolam. Second-Line Treatment: Medications such as IV Phenytoin, Fosphenytoin, Valproic Acid, or Levetiracetam. Third-Line Treatment: In severe cases, use ICU sedation with IV Propofol, Pentobarbital, or Ketamine to control refractory seizures.

Antiparkinsonian Drugs Overview



DefinitionAntiparkinsonian drugs are utilized to manage Parkinson’s disease (PD), a neurodegenerative disorder characterized by tremors, muscle rigidity, bradykinesia (slowness of movement), and postural instability.Types of Antiparkinsonian Drugs

Dopaminergic Agents

  • Levodopa (L-DOPA): Converts into dopamine, making it the most effective treatment for PD.

  • Side Effects: Include nausea, dizziness, dyskinesias (involuntary movements), and hallucinations.

  • Carbidopa-Levodopa (Sinemet): A combination drug that prevents the breakdown of levodopa; it is considered the first-line treatment for moderate to advanced PD.

Dopamine Agonists

  • Pramipexole, Ropinirole: These medications mimic dopamine and are indicated for early PD or as an adjunct therapy to greater efficacy when added to levodopa.

  • Side Effects: Dizziness, sleepiness, and compulsive behaviors (such as gambling).

MAO-B Inhibitors

  • Selegiline, Rasagiline: They inhibit the breakdown of dopamine in the brain.

  • Side Effects: Mild agitation, insomnia, and nausea.

COMT Inhibitors

  • Entacapone, Tolcapone: They extend the effects of levodopa by inhibiting its breakdown.

  • Side Effects: Diarrhea, dyskinesias, and potential liver toxicity with Tolcapone.

Anticholinergic Drugs

  • Benztropine, Trihexyphenidyl: These act by blocking acetylcholine receptors, which helps in reducing tremors and rigidity.

  • Side Effects: Include dry mouth, urinary retention, and confusion.

Amantadine

  • Mechanism: This drug increases dopamine release and is effective in treating mild PD.

  • Side Effects: Insomnia and peripheral edema.

Pharmacokinetics

  • Absorption: Most medications are absorbed from the gastrointestinal tract, and protein meals can affect the absorption of levodopa.

  • Excretion: Primarily excreted via urine; renal function affects clearance.

Nursing Considerations

  • Monitor vital signs, teaching patients about their medications, and watch for any adverse effects, particularly during treatment initiation or dosage adjustments.

Diuretics Overview



DefinitionDiuretics are medications that help the body expel excess salt and water through increased urine production. They are primarily used to treat conditions such as hypertension, heart failure, and certain kidney diseases.Types of Diuretics

Thiazide Diuretics

  • Examples: Hydrochlorothiazide, Chlorthalidone.

  • Mechanism: These drugs inhibit sodium reabsorption in the distal tubule of the nephron.

  • Side Effects: Can cause electrolyte imbalances and hyperglycemia.

Loop Diuretics

  • Examples: Furosemide (Lasix).

  • Mechanism: They inhibit sodium reabsorption in the loop of Henle.

  • Side Effects: Ototoxicity and dehydration.

Potassium-Sparing Diuretics

  • Examples: Spironolactone.

  • Mechanism: They block sodium reabsorption while conserving potassium.

  • Side Effects: Hyperkalemia, which can lead to serious cardiac problems.

Carbonic Anhydrase Inhibitors

  • Example: Acetazolamide.

  • Side Effects: Electrolyte imbalances such as hypokalemia and possible metabolic acidosis.

Osmotic Diuretics

  • Example: Mannitol.

  • Side Effects: Electrolyte imbalances and dehydration.

Nursing Considerations

  • Regular monitoring of vital signs, electrolyte levels, and fluid status is fundamental due to the potential for imbalances and other adverse effects associated with diuretics.

Psychotherapeutic Medications Overview



DefinitionThese medications are designed to treat mental health disorders, including depression, anxiety disorders, and schizophrenia, by modifying levels of neurotransmitters in the brain.Types of Psychotherapeutic Medications

Antidepressants

  • SSRIs (Selective Serotonin Reuptake Inhibitors): Fluoxetine, Sertraline.

  • SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors): Duloxetine.

  • TCAs (Tricyclic Antidepressants): Amitriptyline.

  • MAOIs (Monoamine Oxidase Inhibitors): Phenelzine.

Antipsychotics

  • Atypical Antipsychotics: Risperidone, are usually preferred due to a lower incidence of side effects compared to typical antipsychotics (like Haloperidol).

Mood Stabilizers

  • Lithium: Requires close monitoring for toxicity due to its narrow therapeutic range.

  • Anticonvulsants: Such as Valproate can also serve as mood stabilizers.

Anxiolytics

  • Benzodiazepines: Diazepam is a common example.

  • Buspirone: A non-sedating anxiolytic option.

Nursing Considerations

  • Regular monitoring of vital signs and medication adherence is essential, alongside educating patients on the side effects and the importance of taking medications as prescribed.

Analgesics Overview



DefinitionAnalgesics are medications used to relieve pain from various conditions, including injuries, chronic pain syndromes, and postoperative pain.Types of Analgesics

Non-Opioid Analgesics

  • NSAIDs (Nonsteroidal Anti-Inflammatory Drugs): Such as Ibuprofen; effective for pain and inflammation.

  • Acetaminophen: Used for mild to moderate pain; with fewer side effects compared to NSAIDs.

  • Cox-2 Inhibitors: Celecoxib, which targets specific pain pathways.

Opioid Analgesics

  • Examples: Morphine, Hydrocodone, Fentanyl; powerful pain medications.

Adjuvant Analgesics

  • Examples: Antidepressants (like Amitriptyline) and anticonvulsants (like Gabapentin) are used to manage neuropathic pain.

Topical Analgesics

  • Examples: Lidocaine patches and Capsaicin cream; localized pain relief options.

Nursing Considerations

  • Consistent assessment of pain levels, providing education on medication use, and ensuring proper hydration is critical for effective pain management.

Anti-inflammatory Medications Overview



DefinitionAnti-inflammatory medications are used to reduce inflammation, pain, and swelling associated with diverse medical conditions.Types of Anti-inflammatory Medications

NSAIDs

  • Examples: Ibuprofen and Naproxen, effective for pain relief but can cause gastrointestinal irritation.

Corticosteroids

  • Examples: Prednisone and Dexamethasone; potent anti-inflammatory agents but with significant side effects like weight gain and increased infection risk.

Anti-gout Medications

  • Specific treatments (like colchicine) for managing acute and chronic gout episodes.

General Nursing Considerations

  • Education: It's essential to emphasize patient adherence to prescribed medications and discuss potential side effects.

  • Monitoring: Regular assessments for both therapeutic and adverse effects should be conducted to ensure patient safety and medication efficacy.