The manufacturer of Topamax® (topiramate) has written to healthcare professionals advising that generic versions of this drug are likely to be available soon due to patent expiry. They also advised that current recommendations indicate that generic substitution should be avoided.
Similar action was taken by the manufacturer of lamotrigine when the patent expired. At this time the Department of Health reassured clinicians that prescribing generically was safe and effective. It is also notable that generic versions of lamotrigine are approximately 90% less expensive than the branded equivalent.
The letter contains references to the National Institute for Health and Clinical Excellence (NICE) and Scottish Intercollegiate Guidelines Network (SIGN) guidelines for epilepsy. The NICE guideline suggests that "changing the formulation or brand of AED is not recommended" but this recommendation is rated as level D and is therefore derived from extrapolated data or expert opinion rather than hard clinical evidence. The SIGN guideline contains no indication for the level of evidence attributed to the similar recommendation in their guideline.
Action: Clinicians should continue to prescribe topiramate as generic. Prescriptions can be branded where this is felt to be clinically appropriate.