Psychotropic drugs
Morbid obesity has been linked to different psychiatric disorders. Depression is the most common psychiatric disorder in the obese population with reported odds ratios (OR) ranging from 1.21 – 5.8 with a stronger association in women 115. There is also a higher risk of anxiety disorders in the obese population (OR 1.27 – 1.40) 115. The prescription of psychotropic drugs is, therefore, relatively common in the bariatric surgery population.
In an in-vitro model studying the dissolution of common psychotropic drugs, ten of 22 psychiatric drugs had a significantly lower dissolution fraction and two had significantly higher dissolution after RYGB compared to preoperatively 116.
Hamad et al. investigated the effect of RYGB on the pharmacokinetics of Serotonin Reuptake Inhibitors (SRI). Patients were taking venlafaxine (N=5), citalopram (N=2), escitalopram (N=2), sertraline (N=2), or duloxetine (N=1) 117. AUC values decreased with 54% (36 – 80%) one month after surgery in comparison with pre-operative levels. In most patients AUC values returned to baseline or exceeded baseline at six months after surgery 117.
Marzinke et al. measured escitalopram plasma levels in four subjects two weeks before versus two and six weeks after RYGB. Two weeks after surgery, escitalopram plasma levels decreased by 4 – 71%. Samples collected six weeks after surgery showed a further decrease with 16 – 19% 118.
Roerig et al. measured the AUC of duloxetine and sertraline in RYGB patients and matched controls 119,120. For sertraline both the AUC0-10,5 (124.4 +/- 55.5 ng-hr/ml vs 314.8 +/- 129.6 ng-hr/ml) and Cmax (19.0 +/- 7.8 ng/ml vs 48.7 +/- 19.1 ng/ml) were significantly lower 9-15 months after RYGB surgery119. For duloxetine, AUC0- (646.74 +/- 79.7 vs 1119.91 +/- 593.40) and Tmax (2.2 +/- 0.86 vs 6.0 +/- 2.17) were significantly lower in the RYGB group 9 – 15 months after surgery 120.
These studies suggest that health care professionals should be aware of decreased serum concentrations when prescribing anti-depressants and anti-psychotics drugs to bariatric surgery patients, especially in the first few weeks and months after surgery 117–120. Although no information was provided on the mental status of patients in the above mentioned reports, prescribers should, monitor patients for signs of therapy failure, particularly in the first year after bariatric surgery.