Behavioural effects of the new anticonvulsants

Of the 9 new anticonvulsants that have been marketed recently in the UK or US, a number appear to have either adverse or beneficial effects on behavio ur. There is now a considerable database of information, in terms of the nu mber of patients treated and/or the number of published reports, on vigabat rin, lamotrigine, gabapentin and topiramate, Oxcarbazepine has been availab le in some centres for several years and there is extensive experience with the drug in Scandinavia. It appears that the profile of adverse and benefi cial effects is similar to that of carbamazepine. Behavioural effects have probably been greatest with vigabatrin, with psych osis, depression and other behavioural problems recorded, but the use of th is drug has been limited because of the concern about visual field constric tion. The cognitive and behavioural effects of topiramate have caused conce rn, but these may be much less of a problem if lower starting dosages and e scalation rates are used. Psychosis and depression have been associated wit h topiramate, as they have with another carbonic anhydrase inhibiting drug, zonisamide. Although zonisamide has been used for many years in Japan and Korea, experience elsewhere with this drug is currently very limited. Gabap entin seems to be less associated with adverse behavioural effects than som e of the other new anticonvulsant drugs. The reports of behavioural disturb ance with gabapentin in children may be related to dose escalation. Behavio ural disturbance as a direct result of lamotrigine seems to be uncommon, al though indirect effects on behaviour, through the so-called 'release phenom enon' from improved seizure control and consequent ability to misbehave, ca n occur. Positive behavioural effects have been described with several of the new an ticonvulsants, particularly gabapentin, lamotrigine and oxcarbazepine; all of these drugs may have mood-levelling effects that could be of value in tr eating affective disorders. The information on tiagabine and levetiracetam is too limited to allow any firm conclusions to be drawn with regard to pos itive or negative behavioural effects. When interpreting reports of behavioural changes with anticonvulsants, it i s important to avoid attributing the effect to the drug when one or more of the other multiple causes of behavioural disturbance in people with epilep sy may be responsible or when an indirect effect such as 'forced normalisat ion' may be the cause. Many of the published studies are retrospective and unblinded rather than double-blind, placebo-controlled, prospective trials, implying that much of the data must be interpreted with caution at this st age.