The generics manufacturer Accord has confirmed that they will be out of stock of Phenytoin sodium capsules from January 4th 2020 until early May 2020.
Phenytoin is classified by the Medicines and Healthcare products Regulatory Agency (MHRA) as a Category 1 anti-epileptic drug and the advice for these drugs is for the prescriber and dispenser to ensure that the patient is maintained on a specific manufacturer’s product. However when there is a shortage of a particular product it may not be possible to maintain the patient on a specific product.
An alternative phenytoin sodium 100mg capsules manufactured by Flynn Pharma is available, however switching to an alternative formulation required monitoring and may also require specialist support, advice or referral.
Advice for Healthcare professionals
- Identify patients currently prescribed phenytoin sodium 100mg capsules
- If the patient is prescribed and/or dispensed the Accord product normally:
- If clinically appropriate they will need to be switched to the Flynn Pharma product with no initial dosing adjustments but patients will need to be closely monitored during the switching period
- If the Flynn Pharma product is not clinically appropriate, alternative phenytoin formulations should be considered. Prescribers and pharmacists should work together to understand which formulations are available and ensure the patient receives the correct dose of the alternative product and any monitoring requirements are followed
- Prescribers should ensure that any patient whose epilepsy is unstable is referred to specialist care for management
Alternative phenytoin formulations
There are a number of alternative licensed phenytoin preparations available. It is important to note that doses of sodium salt preparations (capsules, tablets and injection) require dose conversion when switching formulations from and to phenytoin base preparations (suspension and Infatabs®).
Although 100mg of phenytoin sodium is equivalent to 92mg of phenytoin base on a molecular weight basis, these molecular equivalents are not necessarily biologically equivalent.
In practice, the conversion used is:
Phenytoin sodium 100mg is equivalent to phenytoin base 90mg so 100mg capsule is equivalent to 90mg (15mls) suspension.