Primidone Shortage: What Providers and Prescribers Need to Know in 2026

While Primidone is not on the FDA's official drug shortage list in 2026, clinicians managing epilepsy and essential tremor patients continue to field calls about pharmacy-level stock unavailability. This guide is designed to help neurologists, epileptologists, movement disorder specialists, and primary care providers understand what's happening, how it affects their patients, and what clinical tools are available.

Clinical Background: Primidone's Role in 2026

Primidone (Mysoline) is a first-generation barbiturate-type anticonvulsant FDA-approved for grand mal, psychomotor, and focal epileptic seizures since 1954. It is also widely used off-label as a Level A evidence-based treatment for essential tremor by the American Academy of Neurology (AAN), though propranolol remains the only FDA-approved pharmacotherapy for ET.

Primidone is metabolized to two active compounds: phenobarbital (15-25% of an oral dose) and phenylethylmalonamide (PEMA). Both contribute to anticonvulsant activity. The therapeutic serum concentration range is 5-12 mcg/mL. The drug is not a DEA-controlled substance, though abrupt discontinuation risks are severe.

Current Availability Status: What the Data Shows

The FDA does not list Primidone as in shortage as of 2026. Generic Primidone is produced by multiple manufacturers and available through major pharmaceutical wholesalers. However, several dynamics create sporadic availability challenges at the pharmacy dispensing level:

Low dispensing volume. Primidone is prescribed significantly less than newer antiepileptic drugs. Community pharmacies in lower-volume markets may not maintain consistent inventory, relying on order-on-demand sourcing.

Dosage strength variability. The 50 mg tablet — commonly used in ET titration — is stocked by fewer pharmacies than the 250 mg tablet, creating patient-specific access issues even when the drug is technically "available."

Generic fragmentation. Multiple generic manufacturers mean different pharmacies source from different suppliers. Disruptions at any single manufacturer may affect specific pharmacy chains disproportionately.

Clinical Risk Assessment: Who Is Most Vulnerable?

Not all Primidone patients face equal risk from supply gaps. Providers should prioritize immediate intervention for:

Patients with history of status epilepticus. Abrupt discontinuation in this population carries the highest risk of life-threatening events.

Patients on Primidone monotherapy. Those without concurrent antiepileptic coverage face the greatest vulnerability to seizure breakthrough if supply is interrupted.

Patients who have failed multiple other antiepileptics. For these patients, switching may not be straightforward and alternatives may be limited.

Elderly patients on Primidone for essential tremor. A return of severe tremor can cause falls, inability to perform ADLs, and acute functional decline.

Clinical Guidance: Bridging Strategies and Alternatives

If a patient cannot locate Primidone, providers have several options depending on clinical context:

Phenobarbital bridge (epilepsy patients): Since Primidone is substantially metabolized to phenobarbital, a carefully calculated phenobarbital dose may be used as a short-term bridge. Note that phenobarbital is a Schedule IV controlled substance. This requires careful dosing calculation and close clinical monitoring. Serum level monitoring is strongly recommended.

Levetiracetam (epilepsy): Levetiracetam can be used adjunctively or as an alternative for partial-onset and generalized seizures. It has a favorable drug interaction profile and no controlled substance status. Titration over 2-4 weeks is standard.

Propranolol (essential tremor): For ET patients who are not contraindicated (no asthma, COPD, or significant bradycardia/heart block), propranolol 80-320 mg/day is the alternative with the strongest evidence base and FDA approval.

Topiramate (essential tremor): Off-label option with Level B evidence from AAN guidelines. May be initiated at 25 mg/day and titrated up. Primary side effects include word-finding difficulty, paresthesias, and weight loss.

39,483+ patients found their medications in stock

39K+

Find Primidone In Stock Today →

Drug Interaction Considerations When Switching

Providers should be aware that Primidone — through its phenobarbital metabolite — is a potent CYP enzyme inducer (CYP2C, CYP3A). When Primidone is discontinued, the loss of this enzyme induction may increase serum levels of co-administered drugs metabolized by these pathways. Key concerns include:

Warfarin INR may increase significantly when Primidone is stopped — monitor closely and adjust dose.

Oral contraceptives may become more effective (though not a clinical concern, patients should be informed).

Corticosteroid, antiviral, and immunosuppressant levels may rise — review all co-medications before stopping Primidone.

Helping Patients Find Primidone: Resources for Your Practice

Refer patients to medfinder for providers — a service that calls local pharmacies on behalf of patients to identify which ones have their specific medication in stock, then texts the results to the patient. This significantly reduces the administrative burden on both patients and practice staff dealing with "I can't find my Primidone" calls.

See also: How to Help Your Patients Find Primidone in Stock: A Provider's Guide