Drug Interactions Newsletter

Volume 1, Issue 8, 03/10/2009

Question

How does coadministration of the antidepressant paroxetine (Paxil®; Paxil CR®) with atomoxetine (Strattera®) cause a 6 to 8 fold increase in atomoxetine concentrations and is this increase clinically meaningful?

Answer

Atomoxetine (Strattera®) is a selective norepinephrine reuptake inhibitor that is commonly used in the treatment of attention-deficit/hyperactivity disorder (ADHD) in both pediatric and adult patients.   It has the advantage of being a non-stimulant agent and therefore has less diversion potential.  Unfortunately, 20-30% of ADHD patients also suffer from depression that often requires additional treatment with antidepressants, a scenario in which selective serotonin reuptake inhibitors (SSRIs) are likely to be prescribed first-line.(2)  Of the SSRI's that may be used in clinical practice, paroxetine (Paxil; Paxil CR®) is popular for a number of reasons, these include its generic status, broad spectrum of activity and the number of FDA approved indications it holds for various psychiatric conditions.(3)  As such, a situation involving the coadministration of atomoxetine and paroxetine in patients with both ADHD and depression is quite possible.  The problem with this particular combination is that paroxetine has been shown to increase atomoxetine exposure 6 to 8 fold.(1,4)  So, how does paroxetine cause such significant increases in atomoxetine concentrations?.....To read the full answer please LOGIN or SUBSCRIBE NOW.