The CHM has reviewed its 2013 advice on the switching of anticonvulsants between different manufacturers’ products, following feedback and requests for clarification from patients and healthcare professionals.
The updated advice still divides epilepsy drugs into three categories according to the need for brand continuity to be maintained. The CHM also continues to note that the loss of seizure control and/or worsening of side-effects seen around the time of switching between products could be chance associations, but that the effect of switching cannot be ruled out in all cases.
The advice for category 1 drugs remains the same, but the CHM has now advised that patient-related factors should be taken into account when deciding whether continuity of supply should be maintained for category 2 and 3 drugs.
For drugs in category 3, differences between alternative products (for example, product name, packaging, appearance, and taste) may be perceived negatively by patients and/or carers, and may lead to dissatisfaction, anxiety, confusion, dosing errors, and reduced adherence. In addition, difficulties for patients with co-morbid autism, mental health problems, or learning disability should also be considered.
For drugs in category 2, similar considerations apply. It may also be necessary to consider clinical factors such as seizure frequency, treatment history, and the potential implications for the individual of having a breakthrough seizure.
The advice for each category, which is based on therapeutic index, solubility and absorption, is now 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, 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. Patient/carer-related factors such as negative perceptions about alternative products should also be taken into account.
Category 3 (levetiracetam, brivaracetam, 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. Other patient/carer-related factors such as negative perceptions about alternative products should also be taken into account.
When 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.
Pharmacists should also be reminded 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 this with both the prescriber and the patient (or carer).