Mr. BW (mаle, 37 yeаrs оld) hаs a past medical histоry оf bipolar disorder and has been stable on valproate semisodium (valproic acid) 1g twice a day for 3 years. He has been admitted to hospital and diagnosed with severe bipolar depression. His psychiatrist deems it appropriate to prescribe lamotrigine in addition and asks you to advise on the starting dose for Mr. BW. What initial dose would you advise?