Folsyra kan kanske påverka lamotrigin

The interaction between folic acid and lamotrigine was unexpected and additional research is required to investigate this further. However, there are grounds to consider such an interaction biologically plausible. Lamotrigine was originally synthesised as one of a series of folate antagonists on the grounds that folate was thought to be pro-convulsant.6 Hence, it is possible that lamotrigine and folate both bind to a common receptor or enzyme site. Alternatively, it could be a pharmacokinetic effect whereby folic acid reduces absorption of lamotrigine from the gastrointestinal tract. There has been surprisingly little research into the mechanism(s) of action of lamotrigine to either include or exclude a possible important effect modification by folic acid. We cannot find any previous report of a clinical interaction of the kind we describe here, although the summary of product characteristics for lamotrigine does report an effect on folate levels. Whatever the cause, the interaction is potentially clinically important because folic acid supplementation might be more likely in some patient groups taking lamotrigine, for example pregnant women12 and as an adjunctive therapy in mood disorder.11 Furthermore, folic acid is present in the doses used in CEQUEL in many over-the-counter vitamin preparations. One clinically important conclusion from CEQUEL is that if a patient with bipolar disorder needs folic acid therapy, then lamotrigine should be avoided (and vice versa). The result raises an intriguing question about the likely efficacy of lamotrigine in countries which fortify wheat flower with folic acid: the US programme has been estimated to provide 100–200 μg of folic acid per day in women of childbearing age.27 It is unclear if this amount is sufficient to reduce the treatment effect.