Q:  Lamotrigine & Oral Contraceptives

 Hi Dr. Phelps,
 
 I'm curious about the nature of drug interactions between OCP's and lamictal.
 
 Every time I fill my lamictal prescription, the pharmacist tells me that lamictal can make my yasmin less effective.  But this is not consistent with what I'm learning in class.  (I'm in a Psych NP program).  In fact, I've had a hard time finding literature to support that idea.
 
 I *have* seen that OCP's increase the rate of clearance for lamictal by up to 50%, causing the need for higher doses, but nothing about interactions the other way.
 
 Also, what of the week of blanks in the typical pack of birth control pills?  Wouldn't that cause my lamictal level to shoot up and does that increase my risk of Stevens-Johnson syndrome?
 
 I know this is sort of a technical question, but it's both personally relevant as well as a future prescriber, it's professionally relevant too.  Even if you can just point me in the right direction on this topic, that would be great! 
 Thanks!

Hello K' --

The first time the pharmacist told that to one of my patients on an oral contraceptive pill (OCP), I asked the lamotrigine representative (GlaxoSmithKline -- the original manufacturer, although now there are generics as well, as you know) for information on this.  If you've ever made such a request, you know that the representative is then responsible for contacting the "medical information specialist", who in turn is responsible for digging up everything the company has on that question and sending it to you.  The point is, I think we get a pretty good database with that maneuver, from which to address your question. 

After reviewing those materials, I tried to write up a summary in plain English: Lamotrigine and Oral Contraceptives.  As you'll see, there are some very tricky subtleties that I think account for the mixed messages you're getting.  I just re-read it. Wow, complicated. It has to be read closely and carefully, or misinterpretations could easily occur.  I think that is what's happening with the pharmacists.  

See what you think -- 

Jim Phelps 

(P.S. surfing around on this topic, I just discovered there’s a similar summary from Mass. Gen. Hosp’s reproductive psychiatry team, also very careful in the wording, you can use as a cross check. Here’s that link. )

Published April, 2009