Q:  Variance of Lab Results

 
12 year old son dx with Bipolar & ADHD 4 yrs. ago. Current meds are 500mg Depakote 2x a day, 150mg lithium am and 300mg pm, 50mg Strattera am, and 50mg Seroquel pm (just changed to 100mg pm today). Depakote level a month ago was 142 and lithium was .8.  Blood levels just checked again.  Depakote level was 84 and lithium was .6.  Symptoms of more frequent mood swings and feeling "antsy" was same with both levels. About to be kicked out of school because of behavior. The timing of both blood tests was the same (9:00 A.M.) and meds were not given in the am before blood work was done.  Takes evening meds about 7:30 P.M.  Dr. says the difference in levels  significant, but cannot explain. Can you explain difference?  Also, thyroid was 4.7 first blood test and 4.9 second test.  Thyroid is being watched but not treated at this time. 
 

Dear Cheryl -- 
Lithium: At 0.2 mEq/L change from one test to the other, the difference in levels is within the range of variation I see, no big deal, in my experience, does not call for an explanation. But I'm sure the Depakote levels are the ones you're referring to here, and indeed that is a very big shift. If this Depakote ER (blue pill), not the older CR version (salmon color), then perhaps it is associated with a change in gastointestinal absorption.  The ER version is know to be less than fully absorbed. Although the figure usually given is 15% unabsorbed, that can vary. Perhaps in your son you just saw it vary toward the very high end, absorbing nearly everything for 3-4 days due somehow to diet (e.g. slower travel times due to less rapid gastrointestinal activity, as occurs with high fat and low fiber meals, for example); then absorbing only 85% or less for a few days due to more rapid transit.  Even this is a stretch, as at best the variation might be 30% according to what I've read. I'll bet that's part of the answer, though. I suppose one could even wonder whether he needs a blood level of 125, i.e. the very maximum recommended; and that with the ER he's falling below that too often, so that you could try switching to the CR version, which theoretically would be less variable. This will also bump the effective dose up somewhat, probably, which might be good at this point (all this of course for review with his doctor who will make the decision, just some ideas to consider). 

While you're at it make sure somebody asks this question: could Strattera be making him worse? If that preceded the Seroquel, for example, and especially if it preceded the Depakote, it should be wondered whether without it he might fail a class or two but not get kicked out -- i.e. if Strattera, which is effectively an antidepressant, is contributing to manic-side symptoms or cycling, then even if it was helping the ADHD it might be making the overall outcome worse. Then again it could be helping and not interfering at all. Just worth thinking about. 

Dr. Phelps