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Well, it must really have been a struggling period for you to endure , with the muscle aches , irritability , intemporate crying spells, and exhaustion , taking a toll on your health and routine lifestyle. I do not understand, the fact that why the doctors have refuted or neglected your symptoms when , these present symptoms of yours can very much be the result of Side effects of Lamictal ( lamotrigine) as well as lamictal being Ineffective , which has lead to depression ( as evident from intemporate crying spells, irritabilty , exhaustion, etc), as correctly pointed out by your doctor.
You see, lamictal 's common side effcts include muscle aches, generalized body aches, fatigue, irritability , dizziness, insomnia, cognitive and memory problems, etc and the fact that you have been placed on this drug since quite a long time , it makes a lot of sense to have such side effects as well as the drug becoming ineffective due to development of resistance of body against the lamictal , which is quite commonly seen in cases of mood stabilizers , as you must have experienced earlier , in case of depakote . You being a case of bipolar disorder , are more likely to end up being depressed , if the mood stabilizers such as lamictal is not working to the best of its ability and hence what we have currently is a depressed state . So, although i do not appreciate your doctor neglecting the typical side effects of lamictal , but , i agree with him that you are in a state of depression and also that duloxetine ,a fairly good anti depressant would be a good option for you. And , besides starting you on Duloxetine , i would suggest that Lamictal should be stopped and instead of it, you should be started with other tried and tested mood stabilizers such as Lithium or Valproate , and let me also mention here that addition of these mood stabilizers becomes essential in a diagnoses of bipolar disorder to prevent any future episode of Hypomania , which may get precipitated on its own , or due to the use of anti depressant , thus making mood stabilizers a mainstay of the treatment for Bipolar disorder.
So, i would suggest that you ask your doctor to replace Lamictal as soon as possible with another good mood stabilizer such as Lithium or Valproate and along with this change , also start you on Duloxetine ,which would take care of the depressive mood.
I am quite sure that his new combination would take care of your symptoms and would alleviate your mucle aches once for and all.
I wish you rapid recovery to the best of health.
I hope my answer serves your query according to your satisfaction .