How to Help Your Patients Find Dilantin in Stock: A Provider's Guide

When a patient on phenytoin can't fill their prescription, it's not just an inconvenience — it's a patient safety event. Missed doses of a narrow therapeutic index antiepileptic drug can lead to breakthrough seizures with potentially life-altering consequences. This guide is written for neurologists, epileptologists, primary care providers, and anyone prescribing Dilantin or generic phenytoin, to help you proactively support your patients during supply disruptions.

Why Missed Doses of Phenytoin Are a Clinical Emergency

Phenytoin has a long half-life (approximately 22 hours in most adults), which provides some buffer. However, patients already at the lower end of the therapeutic range, or those with faster metabolism, can experience breakthrough seizures within 24–48 hours of missed doses. Key risks include:

Status epilepticus: Abrupt discontinuation can trigger seizures that don't stop spontaneously — a life-threatening emergency

Injury risk: A sudden seizure during daily activities (cooking, driving, bathing) can cause serious injury

Driving restrictions: A breakthrough seizure may legally require a patient to stop driving in most states, often for 6–12 months

Proactive Steps to Take Before a Shortage Affects Your Patients

Prescribe 90-day supplies when possible. A 90-day supply builds a buffer against supply disruptions. Check that your patient's insurance covers 90-day fills; mail-order pharmacies often make this seamless.

Document preferred manufacturer in the chart. If your patient has been stable on a specific manufacturer's phenytoin, document that in your EHR. On prescriptions, use 'DAW' and note the preferred manufacturer.

Develop a contingency plan proactively. Determine in advance which formulation changes or manufacturer substitutions you would accept for each patient, what monitoring would be required, and whether any alternative AED would be appropriate. Have this documented before the patient calls in a panic.

Educate patients to report supply issues early. Encourage patients to start filling prescriptions 2–3 weeks before running out. Instruct them to call your office the moment they have trouble finding their medication — don't wait until they're out.

What to Do When a Patient Calls About a Shortage

When a patient contacts your office about an inability to fill their phenytoin prescription:

Triage urgency: How many days of medication does the patient have left? If they are within 3 days of running out, treat this as urgent.

Recommend pharmacy search: Direct the patient to medfinder (medfinder.com) to search for the medication across multiple pharmacies simultaneously, or have your office manager assist with calling local pharmacies.

Clarify acceptable substitutions: Based on your contingency plan, clarify whether a different manufacturer's phenytoin capsule is acceptable, whether a formulation change with dose adjustment is acceptable, and whether any level rechecks are needed.

Provide an emergency bridge if needed: In urgent situations, you may be able to provide a small supply via in-office dispensing, a manufacturer sample, or an emergency prescription to a compounding pharmacy.

Consider compounding: A compounding pharmacy can formulate phenytoin in specific strengths or delivery forms not commercially available. This can be a valuable bridge during oral suspension shortages for pediatric patients.

Managing Patients Who Must Switch Formulations or Manufacturers

If a patient must switch phenytoin manufacturer or formulation, clinical monitoring is warranted:

Switching between manufacturers of the same formulation: Check trough level at 1–2 weeks and 4 weeks post-switch. Counsel on signs of toxicity (nystagmus, ataxia, confusion) and subtherapeutic effect (breakthrough seizures).

Switching between sodium salt and free acid forms: Adjust dose for the ~8% difference in drug content. Recheck trough levels within 1–2 weeks.

Switching from ER to IR formulations: Adjust dosing schedule from once or twice daily to 2–3 times daily. Total daily dose may remain the same or require adjustment based on serum levels.

Resources to Share With Patients

Consider sharing these resources with affected patients:

medfinder.com — calls pharmacies near the patient and texts them results

How to Find Dilantin in Stock Near You — step-by-step guide for patients

How to Save Money on Dilantin — savings programs and coupons for cost-burdened patients

As a provider, you can also use medfinder for providers to help locate medications directly from your practice, reducing the burden on both your staff and your patients during shortage periods.