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Home > Drug Category > Antiepileptic Medication > Topamax and Equivalent

Topamax (Topiramate) Information

Topamax (topiramate) is a prescription antiepileptic drug (AED) with a unique, sulfamate-substituted monosaccharide chemical structure. It is approved as both monotherapy and adjunctive therapy for specific seizure types in adults and children, including Partial Onset Seizures, Primary Generalized Tonic-Clonic Seizures, and seizures associated with Lennox-Gastaut Syndrome. It is also approved for the prophylaxis (prevention) of migraine headaches in adults and adolescents (age 12 and older). Topiramate is often noted for a favourable side effect of weight loss, and it is sometimes used off-label for conditions such as essential tremor and alcohol dependence. Its exact mechanism of action is multifaceted: it blocks voltage-gated sodium channels, enhances the activity of the inhibitory neurotransmitter GABA, and blocks the activity of the excitatory neurotransmitter Glutamate at the AMPA/Kainate receptor subtype. It is also a weak inhibitor of the carbonic anhydrase enzyme. Topiramate is well-absorbed orally, with a bioavailability exceeding 80%. It has a relatively long elimination half-life of approximately 21 hours, allowing for once- or twice-daily dosing. It is predominantly eliminated unchanged by the kidneys.

Topamax Side Effects

The side effect profile of Topamax is notable for its impact on cognitive function and metabolism. The most common side effects are often referred to as "brain fog" and include: paresthesia (tingling or numbness in the extremities), dizziness, drowsiness (somnolence), fatigue, anorexia (loss of appetite) leading to weight loss, and various cognitive/memory problems (e.g., difficulty concentrating, word-finding difficulty, and slowed thinking). Changes in taste perception are also common.

However, serious side effects can occur, and if any of the following symptoms are experienced, a patient should seek immediate medical attention:

• Acute Myopia and Secondary Angle-Closure Glaucoma: A rare but serious ocular syndrome that can lead to permanent vision loss if not addressed immediately. Symptoms include sudden eye pain, eye redness, or blurred vision, typically occurring in the first month of therapy.

• Hyperammonemia/Encephalopathy: Elevated ammonia levels in the blood, which may lead to confusion, vomiting, and decreased consciousness. This risk is heightened when taken with valproic acid.

• Kidney Stones: The risk is increased due to the drug's mechanism of action; patients should ensure adequate fluid intake.

• Metabolic Acidosis: Topiramate can cause an increased level of acid in the blood, often associated with its inhibition of carbonic anhydrase. Symptoms include fatigue, loss of appetite, fast breathing, or confusion. Periodic measurement of serum bicarbonate is recommended.

• Oligohidrosis and Hyperthermia: Decreased sweating (oligohidrosis) and a risk of dangerously high body temperature (hyperthermia), especially in children exposed to warm weather or strenuous activity.

• Suicidal Thoughts and Behaviour (Boxed Warning for AEDs): Like all antiepileptic drugs, it can increase the risk of suicidal ideation and actions. Patients should be monitored for sudden changes in mood or behaviour.

• Visual Field Defects: Loss of vision in part of the visual field. This effect may be progressive and may require discontinuation of the drug.

Topamax Precautions

Topamax is contraindicated in patients with a history of hypersensitivity to topiramate or its components. Due to the risk of fetal harm (specifically oral clefts), women of childbearing potential should discuss the risks and benefits and, if choosing to use Topamax, may need to use birth control with a higher estrogen dose, as topiramate can decrease the effectiveness of hormonal contraceptives (especially at doses above 200 mg/day). Dosage adjustments are necessary for patients with renal impairment, as the kidneys primarily eliminate the drug. It should be used with caution in patients with a history of kidney stones, liver disease, or a predisposition to metabolic acidosis (e.g., severe lung or breathing problems). Avoid using with Valproic Acid due to the increased risk of hyperammonemia/encephalopathy. Abrupt discontinuation should be avoided, as it may lead to an increase in seizure frequency or the occurrence of status epilepticus. Patients should avoid alcohol and other central nervous system (CNS) depressants due to increased risk of dizziness, drowsiness, and cognitive side effects.

Do I need a prescription to order Topamax?

Yes, a prescription is required from your physician to order Topamax.