Learned Today: Medication Interactions

One of my patients seen today is taking multiple medications: quetiapine (Seroquel), lithium, carbamazepine, thyroid, and occasionally a little tiny bit of clonazepam (Klonopin). Those are just "my" medications, the ones I prescribe. (This is unfortunately not unusual: at Harvard's bipolar clinic, the average number of psych' medications their patients are taking is four) She's also taking diovan, verapamil, omeprazole, HCTZ, and Relafen from her primary care doctor. You don't have to recognize those medication names to see the problem, which pharmaco-experts are always warning about: the potential for interactions between drugs.

In case you've not already found one, here's a relatively simple medication-interaction checker. But before you get too excited: the problem is the interactions you'll find listed are too inclusive. Lots of interactions listed here are theoretical more than real. The computer lists things that in clinical practice just don't really cause much trouble. So you, a patient or family member, might see some interaction listed and think there's something to worry about when a doctor who's used these medications for years knows it's not a common problem.

For example, in my patient's case, carbamazepine's potential "neurologic side effects" are more likely when used in combination with lithium. This interaction shows up on most lists; on the checker linked above, it is said to be "moderate in severity". But it is also "poorly documented", which I presume reflects the fact that we who use these two together only rarely see any evidence of this problem. It's nice for me to know about, but for you to worry about? No, and that's why I would only recommend these drug interaction checkers to patients and families with caution.

If your doctor is in a hurry (whose isn't?), you could cause trouble by asking her/him to review a list of medication interactions you printed out. On the other hand, interactions -- as could occur between several of the medications my patient today is taking -- are worth checking: by somebody, at some point. So if you think maybe your doctor hasn't had time to run a check; and if you have a good enough relationship to carefully raise the issue of interactions without ruining your connection with this doc'; then you might want to run your medications through a checking program such as the one listed above.

Doctors really don't have a good system for monitoring for interactions, and patients/families could become a useful part of the team by running these checks and bringing in the list for review -- as long as they understand that some of the interactions will be minor, or "poorly documented", and can be safely ignored in the majority of cases. Obviously the best time to run that check would be each time a new medication was going to be added to the list, before that medication was started. But here's where you have to remember: the point of the list is to make one think, and consider what's known, not to raise a red flag about every potential interaction (because the programs are not good at telling which issues merit a red flag or a yellow one or a green one!).

So you might say to the doc's nurse: "I really trust Dr. Jones' judgment, and I want to take this medication with confidence, so I'd just like to make sure that the medication interactions I've found are minor and not an issue we need to worry about, as I understand is common with these lists. Can you just check with Dr. Jones and make sure there's nothing here to worry about? I'll assume that unless I hear back from you, I should go ahead with this new medication. I can email you the list if you like" [cut/paste]. You'll see that this approach is similar to the general approach outlined in my essay on Talking with Doctors. It's tricky. It's new. Still a good idea, I think, but blame me if your doctor doesn't like it, and be prepared for that to happen! Good luck with the process.