Interactions between angiotensin AT1 receptor antagonists and second-generation antiepileptic drugs in the test of maximal electroshock

The anticonvulsant activity of angiotensin AT(1) receptor antagonists, losartan (2-n-butyl-4-chloro-5-hydroxymethyl-1-[(2 '(1H-tetrazol-5-yl)-biphenil-4-yl)methyl]imidazole) and telmisartan (49-[(1,49-dimethyl-29-propyl[2,69-bi-1H-benzimidazo]-19-yl)methyl]-[1,19-biphenyl]-2-carboxylic acid), has been reported recently. It is suggested that AT(1) receptor antagonists may affect the protective action of antiepileptic drugs. The aim of this study was to determine the influence of losartan and telmisartan on the anticonvulsant activity of some second-generation antiepileptics (lamotrigine - LTG, oxcarbazepine - OXC, and topiramate - TPM). For this purpose, the maximal electroshock seizure (MES) test in mice was used. Additionally, the drug combinations were checked for adverse effects in the passive avoidance and chimney tests. In the MES test, losartan at the doses of 30 and 50mg/kg, administered intraperitoneally (i.p.), potentiated the protective action of LTG (P<0.01). This interaction was not accompanied by a significant change of LTG level either in plasma or in the brain. Telmisartan at the dose of 30mg/kg i.p. enhanced the anticonvulsant action of TPM (P<0.01). However, this interaction was pharmacokinetic in nature, as telmisartan significantly increased plasma and total brain concentrations of TPM (P<0.001). The combinations of AT(1) receptor antagonists with antiepileptic drugs did not affect retention in the passive avoidance test or motor coordination in the chimney test. The potentiation of the anticonvulsant action of LTG by losartan probably on account of pharmacodynamic interactions, make this combination important for further experimental and clinical studies. The combination of telmisartan and TPM is less beneficial due to pharmacokinetic interactions.