When You Can't Get Phenytoin XR, You Still Have Options

Running out of a seizure medication is one of the most stressful things an epilepsy patient can experience. If you've been trying to fill your Phenytoin XR prescription and keep hitting dead ends, you might be wondering whether there's something else you can take instead.

The short answer: yes, there are alternatives — but switching seizure medications should always be done carefully, under your doctor's guidance. In this article, we'll walk you through what Phenytoin XR is, how it works, and four real alternatives your doctor might consider.

Important: Never stop taking Phenytoin XR or switch medications on your own. Abruptly stopping an anticonvulsant can trigger dangerous seizures, including status epilepticus. Always talk to your doctor first.

What Is Phenytoin XR?

Phenytoin XR (also sold as Dilantin Kapseals and Phenytek) is an extended-release capsule used to prevent seizures in people with epilepsy. It's been in use since 1939, making it one of the oldest and most well-studied seizure medications available.

Phenytoin XR is prescribed for:

• Generalized tonic-clonic (grand mal) seizures
• Complex partial seizures
• Seizure prevention after neurosurgery

It comes in 100 mg, 200 mg, and 300 mg extended-release capsules and is typically taken once or twice daily. For a complete guide, see What Is Phenytoin XR? Uses, Dosage, and What You Need to Know.

How Does Phenytoin XR Work?

Phenytoin XR belongs to the hydantoin anticonvulsant drug class. It works by blocking voltage-dependent sodium channels in the brain. These sodium channels are responsible for the rapid electrical firing that causes seizures. By stabilizing these channels, Phenytoin prevents the abnormal electrical activity from spreading.

What makes Phenytoin unique is its narrow therapeutic index. The effective blood level is between 10 and 20 mcg/mL, and levels above 20 can quickly cause side effects like nystagmus (involuntary eye movements), ataxia (loss of coordination), and even toxicity. This is why regular blood level monitoring is required.

Learn more in our detailed guide: How Does Phenytoin XR Work?

4 Alternatives to Phenytoin XR

If you're unable to find Phenytoin XR or if your doctor thinks you might do better on a different medication, here are four commonly considered alternatives. Each one works for similar seizure types but has its own pros and cons.

1. Carbamazepine (Tegretol, Tegretol XR)

What it treats: Focal (partial) seizures and generalized tonic-clonic seizures

How it works: Like Phenytoin, Carbamazepine blocks sodium channels to prevent seizure spread. It's considered a first-generation anticonvulsant.

Pros:

• Well-studied and effective for the same seizure types as Phenytoin
• Available in extended-release form for once- or twice-daily dosing
• Fewer cosmetic side effects (no gum overgrowth or excess hair growth)

Cons:

• Still has many drug interactions (like Phenytoin, it induces liver enzymes)
• Can cause a serious rash, including Stevens-Johnson syndrome — genetic testing for HLA-B*1502 is recommended for patients of Southeast Asian ancestry
• May worsen absence or myoclonic seizures
• Requires blood monitoring (CBC, liver function)

Typical cost: Generic Carbamazepine ER starts around $15 to $40 for a 30-day supply with a coupon.

2. Levetiracetam (Keppra, Keppra XR)

What it treats: Focal seizures, generalized tonic-clonic seizures, and myoclonic seizures

How it works: Levetiracetam works differently from Phenytoin. It binds to a protein called SV2A in the brain, which helps regulate the release of neurotransmitters and reduces seizure activity.

Pros:

• Very few drug interactions — a major advantage over Phenytoin
• No therapeutic drug monitoring required
• Available in generic and brand forms at affordable prices (starting around $10 to $25 per month)
• Often used as a first-line seizure medication
• Safe in a wide range of doses

Cons:

• Can cause mood changes, irritability, or behavioral issues in some patients
• Drowsiness and fatigue are common initially
• Not as effective for some patients who respond well to sodium channel blockers

Typical cost: Generic Levetiracetam starts around $10 to $25 for a 30-day supply.

3. Lamotrigine (Lamictal, Lamictal XR)

What it treats: Focal seizures, generalized tonic-clonic seizures, and Lennox-Gastaut syndrome seizures

How it works: Lamotrigine stabilizes sodium channels (similar to Phenytoin) and also modulates calcium channels and glutamate release.

Pros:

• Broad-spectrum — effective for multiple seizure types
• Generally well-tolerated with fewer cognitive side effects
• Weight-neutral (doesn't typically cause weight gain)
• Available as affordable generic

Cons:

• Requires very slow dose titration over several weeks to reduce the risk of serious rash (Stevens-Johnson syndrome)
• Interactions with Valproic Acid (requires dose adjustment)
• Not ideal if you need rapid seizure control — takes weeks to reach therapeutic dose

Typical cost: Generic Lamotrigine starts around $10 to $30 for a 30-day supply.

4. Valproic Acid (Depakote, Depakote ER)

What it treats: Multiple seizure types including absence seizures, tonic-clonic seizures, and complex partial seizures

How it works: Valproic Acid increases levels of GABA (a calming neurotransmitter) in the brain and also blocks sodium channels.

Pros:

• Broad-spectrum — one of the most versatile anticonvulsants
• Effective for seizure types that Phenytoin doesn't cover well (like absence seizures)
• Well-established, decades of clinical use

Cons:

• Not safe during pregnancy — causes neural tube defects and other birth defects (FDA Pregnancy Category X for migraine prevention)
• Can cause weight gain, hair loss, and tremor
• Risk of liver toxicity, especially in children under 2
• Requires blood monitoring (liver function, blood counts, drug levels)

Typical cost: Generic Valproic Acid ER starts around $15 to $45 for a 30-day supply.

How to Talk to Your Doctor About Switching

If you're considering an alternative to Phenytoin XR, here are some things to discuss with your neurologist:

• Your seizure type: Not all alternatives work for all seizure types
• Your current seizure control: If Phenytoin has been working well, your doctor may want to find it rather than switch
• Other medications you take: Phenytoin has many drug interactions, and your new medication might interact differently with your other drugs. See our drug interactions guide
• Side effects you've experienced: If you've had gum overgrowth, excess hair growth, or other Phenytoin-specific side effects, switching might actually improve your quality of life
• Pregnancy plans: Some alternatives (especially Valproic Acid) are not safe during pregnancy
• Cost: Most alternatives are available as affordable generics

Final Thoughts

Not being able to fill your Phenytoin XR prescription is stressful, but it doesn't mean you're out of options. Carbamazepine, Levetiracetam, Lamotrigine, and Valproic Acid are all proven seizure medications that your doctor can consider as alternatives.

Before making any changes, use Medfinder to check whether Phenytoin XR is available at a pharmacy near you — the supply situation can change daily. And if you do need to switch, work closely with your neurologist to make the transition as safe as possible.

For more on finding your current medication, see How to Find Phenytoin XR in Stock Near You.