Question about how Tegretol lowers your Lamictal serum

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A few months ago I was on 1200 mg of Tegretol and 400 mg of Lamictal a day. At the time my seizures were well controlled. Due to side effects, the Dr lowered my Tegretol level to 800 mg a day and I kept taking the 400 mg of Lamictal a day. I started to have simple partial seizures somewhat often that I was not getting when I was taking 1200 mg Tegretol/400 mg Lamictal.

My question about the way Tegretol lowers your Lamictal serum is at what point when the Tegretol dose is reduced does the Lamictal level start to go up?

Unfortunaltly I didn't measure the Tegretol and Lamictal levels when I was only taking 800 mg of Tegretol. I thought that the Lamictal serum level would rise enough from dropping the Tegretol to 800 mg to control the seizures to make up for dropping the Tegretol dose to 800 mg. When I was on 1200 mg Tegretol/400 mg Lamictal my levels were 7.4 for Tegretol and 2.7 for Lamictal. Once I raised the Lamictal to 500 mg my Tegretol was at 8.5 and my Lamictal was at 4.4. I know the therapeutic range for Lamictal is 2-20. My Dr even said as long as the Lamictal level is at least at 2 it should be helping. I did feel "more stable" when I raised the Lamictal from 400 mg to 500 mg. I am hoping to start taking Vimpat in a couple of months and then completly get off Tegretol. I am just wondering how much the Lamictal level will go up once I'm off the Tegretol.
 
Tegretol can reduce Lamictal serum concentrations by approximately 40%.

So you're right to keep on top of things -- while you reduce the Tegretol, and also when it's completely discontinued, you will likely need to keep adjusting the Lamictal dose downward to compensate. And during the tapering process it's important to monitor how you feel to make sure you aren't experiencing Lamictal toxicity.

Since there is a wide therapeutic range for Lamictal, there is no official target dose or blood serum level. Basically whatever works for you is...whatever works for you. My Lamictal dosage is 175mgs/day, and my blood serum level is about 5.0 (considered low by my docs), but it's enough to give me complete seizure control. Your results will almost certainly vary.
 
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