Epilepsy Medication Switching Risks During Shortages

For most medications, switching between brands or generics is straightforward. For epilepsy drugs, it can be dangerous. Medicine shortages that force epilepsy patients to switch brands or medications carry real risks — including breakthrough seizures. Here's what you need to know.

⚠️ Critical Safety Information: If you have epilepsy and cannot obtain your usual medication, contact your neurologist, epilepsy nurse, or GP before making any changes. Do not stop anti-epileptic drugs abruptly — this can trigger seizures or status epilepticus, which is a medical emergency.

Why Epilepsy Drugs Are Different

Anti-seizure medications (ASMs) have characteristics that make them uniquely sensitive to supply disruptions:

Narrow Therapeutic Index

Many epilepsy drugs have a narrow therapeutic index — meaning the difference between an effective dose and a toxic or sub-therapeutic dose is small. Even minor variations in blood levels can lead to breakthrough seizures or side effects. This is why the MHRA classifies several ASMs as Category 1 medicines: patients should be maintained on a specific manufacturer's product.

Category 1 Anti-Epileptic Drugs

The MHRA categorises anti-epileptic drugs based on switching risk:

Category	Risk Level	Medicines
Category 1	⚠️ High risk — maintain specific brand	Phenytoin, carbamazepine, phenobarbital, primidone
Category 2	Caution with switching	Valproate, lamotrigine, perampanel, retigabine, rufinamide, clobazam, clonazepam, oxcarbazepine, eslicarbazepine, zonisamide, topiramate
Category 3	Lower risk switching	Levetiracetam, lacosamide, tiagabine, gabapentin, pregabalin, ethosuximide, vigabatrin, brivaracetam

Bioavailability Differences

While generic medicines contain the same active ingredient in the same dose, the formulation (the tablets, capsules, or liquid the drug is delivered in) can affect how the drug is absorbed. For most medicines, these differences are clinically insignificant. For narrow therapeutic index drugs like phenytoin or carbamazepine, even small differences in absorption can tip a patient from seizure-free to having breakthrough seizures.

What Happens When Epilepsy Drugs Run Short

When an epilepsy medication faces a shortage, patients may be forced to:

Switch from their usual brand to a different manufacturer's version
Switch to a different formulation (e.g., from modified-release to immediate-release tablets)
Switch to a different anti-epileptic drug entirely
Go without medication temporarily (the most dangerous option)

Real-World Consequences

Breakthrough seizures caused by medication switches can have devastating consequences:

Driving licence loss: A single seizure means losing your driving licence for at least 12 months under DVLA rules
Employment impact: Seizures at work can lead to safety concerns and job loss, particularly in safety-critical roles
Injury risk: Uncontrolled seizures carry risks of falls, fractures, burns, and drowning
SUDEP risk: Sudden Unexpected Death in Epilepsy (SUDEP) risk increases with uncontrolled seizures
Status epilepticus: Abrupt medication withdrawal can trigger prolonged seizures requiring emergency treatment

Which Epilepsy Drugs Have Faced Shortages?

Recent and current epilepsy medication supply issues include:

Carbamazepine: Intermittent supply issues with specific brands, problematic given its Category 1 status
Sodium valproate: Some formulations have faced intermittent availability issues
Phenytoin: The most critical shortage risk due to narrow therapeutic index and limited suppliers
Clobazam: Periodic supply constraints
Lamotrigine: Generally stable but occasional brand-specific issues

What to Do If Your Epilepsy Medication Is Unavailable

Immediate Steps

Do NOT stop your medication — continue taking whatever you have while seeking supply
Contact your pharmacist immediately and ask them to source your specific brand from alternative wholesalers
Try other pharmacies — call ahead and specify the exact brand you need
Contact your epilepsy nurse or neurologist — they can provide urgent clinical advice and may have access to hospital pharmacy supplies
Request an emergency supply from any pharmacy if you're about to run out

If You Must Switch

If switching becomes unavoidable:

For Category 1 drugs: this should be supervised by your neurologist with blood level monitoring
For Category 2 drugs: monitor closely for seizure activity and side effects for at least 2 weeks after switching
For Category 3 drugs: switching is generally safe, but remain vigilant
Keep a seizure diary during and after any medication change
Ensure your emergency contacts know about the medication change

Advocacy and Resources

Epilepsy charities have been vocal about the risks of medication shortages:

Epilepsy Action — campaigns for supply continuity and provides patient support
Epilepsy Society — clinical guidance on medication switches
MHRA Yellow Card — report any adverse effects from medication switches

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Data sources: DHSC Medicine Supply Notifications · NHSBSA Serious Shortage Protocols · NHS England
Page last updated: 7 February 2026. Data checked daily.

Epilepsy Medication Switching Risks