Everything You Need to Know About Topiramate Extended-Release Capsules

An In-Depth Look at Topiramate Extended-Release Capsules

Topiramate extended-release capsules, sold under the brand name Qudexy XR, are a prescription medication used for treating certain types of seizures in adults and children. It belongs to a class of medications known as anticonvulsants.

While the immediate-release form of topiramate has been available for many years, the extended-release version was more recently approved by the FDA in 2014. It provides a gradual, prolonged delivery of the drug over the day.

For those prescribed topiramate extended-release capsules, understanding how this medication works, its uses, proper dosage, and potential side effects is important. Here is an in-depth look at everything you need to know about this anticonvulsant drug.

Mechanism of Action

Researchers arent entirely sure how topiramate works to control seizures. But it appears to block certain receptors and ion channels in the brain that are involved in the uncontrolled electrical activity that characterizes a seizure.

Some of its mechanisms of action likely include:

Blocks Sodium Channels

By inhibiting sodium ion channels, topiramate can stabilize neurons and reduce the chance of sudden electrical discharges.

Inhibits Calcium Channels

Topiramate obstructs some calcium channels in the brain. This disrupts the influx of calcium ions needed for the excessive neuronal firing of a seizure.

Enhances GABA Activity

The drug enhances the activity of the neurotransmitter GABA, which has inhibitory effects on the central nervous system. This counters the excitatory nerve signals that trigger seizures.

Antagonizes Glutamate

It antagonizes the action of the excitatory neurotransmitter glutamate at certain receptors. This provides anticonvulsant effects.

Through these mechanisms, topiramate extended-release alters nerve signal transmission in the brain, reducing the likelihood of hyperactive electrical activity and seizures.

Approved Uses of Topiramate Extended-Release

In the United States, the FDA has approved topiramate extended-release capsules for the treatment of certain types of epilepsy in adults and pediatric patients 2 years and older. Specifically, it is prescribed for:

Partial Onset Seizures

Also called focal seizures, these originate in just one part of the brain. Qudexy XR can treat partial seizures whether consciousness is impaired or retained.

Primary Generalized Tonic-Clonic Seizures

These seizures, previously called grand mal, involve the entire brain from the outset. They result in a loss of consciousness and violent muscle contractions.

Seizures Associated with Lennox-Gastaut Syndrome

This severe childhood epilepsy disorder causes multiple types of difficult-to-control seizures. Topiramate extended-release is approved for treating associated seizures starting at age 2.

By preventing the aberrant electrical activity involved in these seizure types, the medication can reduce the frequency and intensity of epileptic attacks.

Dosage Information

Topiramate extended-release capsules come in varying strengths, including 25mg, 50mg, 100mg, 150mg, and 200mg capsules. The prescribed dosage will depend on the patient and specific condition being treated.

Starting Dosage

When starting Qudexy XR, the typical recommended initial dosage for adults and pediatric patients 10 years and older is 25 to 50mg taken at bedtime. The starting dose for children 2 to 9 years old is 25mg nightly.

Titration Schedule

The dosage is then slowly increased by 25 to 100mg every 1 to 2 weeks until an effective maintenance dose is reached. Multiple smaller dosage increments are often preferable to minimize side effects.

Target Maintenance Dosage

The therapeutic target dosage varies by patient, but generally ranges between 200 to 400mg daily for adults. In children, the recommended maintenance dose depends on weight. Maximum daily doses are 200mg for patients under 20kg and 400mg for those 20 to 40kg.

Twice Daily Dosing

For some patients who experience side effects, splitting the total daily dose into smaller twice daily doses may improve tolerability.

Maximum Recommended Dosage

Adults should not exceed 400mg per day. For pediatric patients, the maximum dose is 400mg for those over 40kg, 300mg for 20 to 40kg, and 200mg under 20kg.

Exceeding the recommended maximum dosage elevates risks of serious side effects without added benefit.

Clinical Efficacy

Multiple clinical studies have demonstrated the effectiveness of Qudexy XR for reducing seizure frequency in patients with difficult-to-control partial onset seizures and primary generalized tonic-clonic seizures.

Trial in Partial Onset Seizures

A randomized placebo-controlled trial enrolled 85 adults with at least 4 partial onset seizures per month despite taking 1 to 3 antiepileptic drugs. Patients received once daily Qudexy XR or a placebo.

Over the 12 week study, Qudexy XR resulted in a significant 38% greater median reduction in seizure frequency compared to placebo. 39% of the treatment group had at least a 50% decrease in seizures versus 18% of the placebo group.

Trial in Primary Generalized Seizures

In another add-on trial in patients with uncontrolled primary generalized tonic-clonic seizures taking 1 to 3 anti-seizure medications, Qudexy XR demonstrated superiority to placebo in reducing seizure rates over a 20 week period.

The 50% responder rate was 44% in the Qudexy XR group compared to 24% for placebo. The drug decreased median seizure frequency by 32% from baseline versus 16% for placebo.

These and other clinical trials confirm Qudexy XRs efficacy for controlling difficult-to-treat seizures in epileptic patients who require add-on therapy.

Comparison to Immediate-Release Topiramate

The extended-release capsules provide prolonged, gradual release of topiramate over the day. This contrasts with immediate-release topiramate, which is absorbed more rapidly and causes faster peak plasma concentrations.

Some key differences between the two formulations are:

Steady Drug Levels

Qudexy XR was designed to produce more consistent, steady plasma concentrations over 24 hours. Immediate-release topiramate causes a large peak followed by a quick decline.

Once Daily Dosing

The controlled-release beads allow Qudexy XR to be taken just once a day, typically at bedtime. Immediate-release topiramate is taken twice per day to maintain therapeutic levels.

Fewer Side Effects

By eliminating large peaks and troughs in plasma levels, Qudexy XR results in fewer ups and downs in drug exposure. This lowers the risk of concentration-related adverse effects.

Many patients switch from immediate-release to extended-release topiramate if they experience bothersome side effects or poor seizure control on the IR version.

Side Effects and Safety

As with any medication, Qudexy XR can cause some unwanted side effects. However, not every patient experiences every side effect. Some of the more common ones can include:

Dizziness

Numbness or tingling

Nausea

Tiredness

Memory problems

Loss of appetite

Diarrhea

Weight loss

Rarer but more serious side effects may include vision changes, speech issues, kidney stones, high body temperature, and depressed mood or thoughts of suicide. Children may experience tiredness, aggression, and difficulty concentrating in school.

Since Qudexy XR can cause birth defects, women must use effective contraception while taking it and avoid breastfeeding. The dose may need adjustment in patients with kidney problems.

Gradual Dose Titration

Most side effects can be minimized by starting at a low dose and slowly increasing the dosage over several weeks. This allows the body to adjust to the drug.

Twice Daily Dosing

Splitting the total daily dose into smaller morning and evening doses may improve tolerability compared to single bedtime dosing.

Topiramate requires close medical supervision. Alert your doctor if any concerning symptoms develop so the dosage can be adjusted or discontinued if needed.

Drug Interactions

Qudexy XR can interact with some other medications. Its important for prescribers to know all drugs and supplements their patient is taking to identify potential interactions.

Some drugs that can interact with topiramate extended-release include:

Other anticonvulsants

Antidepressants

Antibiotics and antifungals

Antipsychotics

Mood stabilizers

Oral contraceptives

Diuretics

Diabetes medications

Opioid pain relievers

Interactions may lead to increased or decreased drug levels, altered effects, or new side effects. Dosages may need adjustment. Topiramate also inhibits certain liver enzymes, affecting drug metabolism.

Warnings and Precautions

There are some important safety issues to be aware of with Qudexy XR:

Suicidal Thoughts

Antiepileptic drugs like topiramate can increase the risk of suicidal thoughts and behaviors. Close monitoring is essential, especially during dose changes.

Eye Problems

Qudexy XR can cause angle closure glaucoma and vision problems like visual field defects. Discontinue use if any vision loss occurs.

Metabolic Acidosis

The drug may cause increased acid levels in the blood due to kidney problems. This can lead to bone softening and kidney stones.

Cognitive Issues

Topiramate may impair memory, concentration, attention, language skills, and other cognitive abilities. This may be dose-related and reversible by lowering the dose.

Birth Defects

Use in pregnancy may substantially increase the risk of cleft lip and palate as well as other malformations in infants exposed in utero.

Hyperthermia

Taking topiramate with valproic acid or while ill increases the chance of dangerously high body temperature.

Frequently Asked Questions

How do I take Qudexy XR capsules?

Take Qudexy XR capsules whole at bedtime exactly as prescribed. Swallow the capsules whole - do not crush, break, or chew them. The beads inside the capsule provide controlled release of the drug.

Can Qudexy XR capsules be taken with food?

Yes, Qudexy XR can be taken with or without food. Taking it with food may help reduce stomach upset if you experience nausea.

How long does it take for Qudexy XR to start working?

It may take several weeks after starting this medication to experience the full effects on seizure reduction. The dosage is gradually increased over 1-2 weeks until an effective maintenance dose is reached.

What should I avoid while taking Qudexy XR?

Avoid driving, operating machinery, or performing hazardous tasks until you know how the medication affects concentration, alertness, coordination, and vision. Avoid overheating. Limit alcohol use due to increased drowsiness.

When should I contact my doctor?

Call your doctor if you experience vision changes, eye pain, increased seizures, depression or suicidal thoughts, kidney stones, fever, severe muscle pain, or any unusual side effects.

The Bottom Line

For patients with difficult-to-treat epileptic seizures who need add-on therapy, Qudexy XR provides an effective extended-release formulation of the anticonvulsant medication topiramate. By delivering consistent levels throughout the day, it offers seizure reduction with once daily dosing and favorable tolerability.

Under medical supervision, Qudexy XR can significantly decrease seizure frequency and improve quality of life. Understanding proper use, drug interactions, and potential side effects is key to safely managing epilepsy with this treatment.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.