I have never had sodium valproate, it sounds awful due to the drowsiness, cognitive impairment and general 'zonkage.' That is why I cannot tolerate phenytoin--it knocks me the fuck out. I am currently on dexamphetamine SR, venlafaxine XR (Effexor XR) and Lamictal (at 300mg qD). I definately think that the combination of dexamphetamine and the right mood stabilizer (absolutely key, to prevent amphetamine-precipitated mania) is a great combo for bipolar disorder. Everyone has different responses to different mood stabilizers--for me, Lamictal has been the best.
It sounds to me, streetsurfer, like you are on the IR version of effexor, so you might have had a dose wear off during the day and never reached stabilized plasma levels. Try the Effexor XR or BID/TID dosing of itty-bitty portions of regular effexor. Also, maybe upping the Lamictal (slowly, only as fast as you can tolerate it and have no dermal side effects) would help. I know that Lamictal has been a godsend for me as a mood stabilizer, but unlike lithium and phenytoin, it does not stabilize my mood by just zonking me out--it actually has anti-depressive properties in addition to its anticonvulsant properties. I am also bipolar ('BP II,' mainly depression), but your pharmacogenic profile may vary.