Tale of Two Enantiomers (or, when do we really have to worry about QTc prolongation with citalopram?)

[UPDATE 4/19: The FDA revised the warning discussed in this article. Additions from the revised version are shown in orange text.]

A Dickens classicLike many providers, I have always been skeptical about escitalopram (Lexapro). It seemed to come right when the patent on citalopram (Celexa) was going to expire and thus Forest Pharmaceuticals was going to lose a lot of money to generic citalopram producers.

So Forest gave us escitalopram, or S-citalopram, the “good” enantiomer of citalopram (the original citalopram was a racemic mixture of both S– and R-citalopram). We were to believe that giving S-citalopram alone would be more effective,* have fewer side effects, and have fewer interactions.

So, imagine the skepticism when–after years of citalopram being so mainstream that it was the default medication in the STAR*D trial–we received an FDA warning that citalopram has a problematic risk of QTc prolongation, and a directive that we therefore must stop using doses above 40mg [20mg in some patients per the revised warning]!

One can’t be blamed for wondering whether someone was again trying to push us towards using the fancy-pants S-enantiomer-only version. Particularly frustrating was the FDA’s comment that “studies did not show a benefit in the treatment of depression at doses higher than 40 mg per day [emphasis added],” which does not address the fact that higher doses are required to treat anxiety-spectrum disorders.

However, after doing seem research, I can say that there are some patients in whom to consider potential danger with citalopram:

  1. Patients at risk for overdose
  2. Patients taking 2C19 inhibitors [or otherwise at risk of having impaired 2C19 metabolism]
  3. Patients taking other QTc-prolonging agents
  4. Patients with certain conditions

Read on to learn more… [Read more…]

What does this picture have to do with lithium? AND: new monitoring recommendations for lithium

Do you know what this picture may have to do with lithium and drug interactions? Also, learn of an easy new screening test and other lithium monitoring recommendations from a Lancet review so hot off the press that it’s still in press!

[Read more…]