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03 August 2015

Generic lamotrigine equivalent to branded version, study shows

Epilepsy Society has welcomed the findings of a new study which shows that the performance of the generic version of  lamotrigine is equivalent to the original branded version of the the anti-epileptic medication.

The study, led by the University of Maryland, is the first to compare the performance of the branded and generic versions of an anti-epileptic drug, in adults with epilepsy who are taking medication on a long-term basis. Tests are usually carried out in healthy young volunteers after single dose administration.

The latest study looked at 34 patients who were already taking lamotrigine. All the patients were 'generic brittle' meaning they were sensitive to the smallest changes in the concentration of medication in their blood.

During the randomised, double-blind study, patients were repeatedly switched between the two versions of the drug Lamictal, the original brand version of the drug, and a generic lamotrigine. Results showed that few of the patients had worsened seizures or side effects. 

Professor Philip- Patsalos comments

The study was praised by the head of Epilepsy Society's Therapeutic Drug Monitoring Unit, Professor Philip Patsolos. 'There have always been concerns about whether the equivalence of two different versions of one drug  in healthy volunteers translates to therapeutic equivalence in patients with chronic epilepsy,' he said.

'This study shows that in lamotrigine, the generic and branded versions of the drug were bioequivalent, meaning the active ingredients were equally absorbed and distributed in blood.

'Previously we have had to presume that this would be so. Now, in the case of lamotrigine, we know.'

Risk of switching between generic drugs

However Professor Patsalos stressed that the greater issue around switching between two versions of a drug concerned switching from one generic to another generic, rather than from a branded to a generic drug.

'The difference in bioequivalence between a branded and generic drug is about six per cent which for most people is negligible but may be important for someone who is sensitive to small changes,' he continued. 'The difference between one generic and another generic can be much greater with the potential for greater consequences.

'Generic drugs are not inferior to branded drugs and it is not inappropriate to prescribe generic drugs for someone when they are first diagnosed with epilepsy. The most important thing is consistency of supply, meaning that you get the same version of a drug with every prescription.'

The Medicines and Health Regulatory Agency (MHRA) has issued guidelines about the prescribing of anti-epileptic drugs. You can read more about it here.