Q:  Does a Reaction to Tegretol Mean a Reaction to Lamictal ?

   
I began taking Tegretol, after 2 weeks, increased dose to 600 mg.  Within 3 days, I had all the symptoms of Stevens-Johnson Syndrome - 103 fever, rash on neck, chest, arms and palms which began itching after a day and swollen vagina.  White blood cells dropped to 2.5 and Platelette to 142.  My doctor stopped the Tegretol, one week later, blood counts back to normal, rash gone.  Now, my doctor prescribed Lamictal.  I have been reading that the same effect could happen, and that stopping Lamictal at the first sign of problems WILL not guarantee symptoms to be life threatening.  What probability is there that I will reacting to the Lamictal as I did the Tegretol?
 

Dear Ms. A' --
Good to see that you've learned so much already, and know just what you're facing as you consider starting lamotrigine (Lamictal).  I hope it's been a few weeks in between, as that would probably help let your immune system settle down.  (And I hope I'm not so late with this reply as to be completely moot...)

Your doctor could contact her Lamictal representative and ask the company this question, as I bet they actually have some numbers on whether people who have reacted to Tegretol are more likely to react to lamotrigine.  A quick PUB MED search on this subject yielded no results, but that doesn't mean I didn't miss something.  

Theoretically these are two completely different molecules and one would not expect that a reaction to one would predict clearly a reaction to the other.  But I'm not enough of an immunologist to comment further than that.  We do try to avoid "revving up" your immune system when using lamotrigine, commonly recommending avoiding new "allergens" like new shampoos or soaps, etc -- or by just having had an allergic reaction to another medication. 

Final thought:  there is a 5 mg version of lamotrigine, which is much smaller than the common starting place of 25 mg (or in my approach, 12.5 mg), and you could even (if I'm not too late) start with half of that.  Starting with smaller doses clearly lowers the risk of having a severe reaction.  If you haven't started yet, talk to your doctor about taking that kind of cautious approach (if you've not already had that talk...). 

 I've started quite a few patients on lamotrigine who reacted to Tegretol, including one woman who reacted like you did -- but of course my tiny numbers don't mean much, and the manufacturer would be a better source.  Good luck!

Dr. Phelps

Published May, 2003