This move follows a CHM review of spontaneous adverse reaction reports received by the MHRA and publications that reported potential harm arising from switching to a generic anticonvulsant in patients previously stabilised on a branded product. The CHM concluded that while loss of seizure control and/or worsening of side-effects around the time of the switch could be chance associations, a causal role of switching could not be ruled out in all cases.
Antiepileptic drugs grouped into 3 categories based on potential risk
The categories, which are based on therapeutic index, solubility and absorption, are as follows:
- Category 1 (phenytoin, carbamazepine, phenobarbital, primidone) – prescribers should ensure patients are maintained on a specific brand or a specific manufacturer’s generic product
- Category 2 (valproate, lamotrigine, perampanel, retigabine, rufinamide, clobazam, clonazepam, oxcarbazepine, eslicarbazepine, zonisamide, topiramate) – prescribers should make a decision about the need to maintain patients on a particular manufacturer’s product based on clinical judgment and consultation with the patient and/or carer, taking into account factors such as seizure frequency and treatment history
- Category 3 (levetiracetam, lacosamide, tiagabine, gabapentin, pregabalin, ethosuximide, vigabatrin) – it is usually unnecessary to maintain patients on a specific manufacturer’s product unless there are specific concerns such as patient anxiety and risk of confusion or dosing errors.
Where it is deemed necessary for a patient to be maintained on a specific manufacturer’s product, prescribers should either specify a brand name or use the generic drug name plus the name of the relevant manufacturer.
The CHM has also advised pharmacists that if it is necessary to supply a product from a different manufacturer to ensure continuity of supply of an anticonvulsant they should first discuss and agree the matter with both the prescriber and the patient or carer.
Further Information: MHRA