59 - Other medicines

Other medicines

Drug treatment of psychiatric symptoms in the context of other conditions CHAPTER 10 Lithium around the time of bariatric surgery The continued use of lithium throughout the perioperative phases of bariatric surgery requires particularly close monitoring. The following guidance is based on available case reports and expert opinion.40 ■ ■Monitor lithium plasma levels preoperatively and perform a scale-­based clinical assessment of mood. ■ ■Educate the patient preoperatively on the importance of drinking 2.5–3 litres of fluid per day (including liquid meal replacement). ■ ■Postoperatively assess for toxicity by monitoring lithium plasma levels and renal function weekly for 6  weeks (as fluid intake gradually increases), 2-­weekly for 6  months and monthly thereafter. Resume usual lithium monitoring 1 ­year post-­ bariatric surgery. ■ ■If plasma levels increase by >25% or approach 1.2mmol/L consider decreasing the lithium dose. ■ ■Withhold lithium if signs of toxicity are present and review the dose. ■ ■To prevent dehydration, counsel the patient to alert their physician or psychiatrist in case of any changes in food or fluid intake or severe vomiting. ■ ■Monitor mental state periodically, using formal rating scales if possible. Other medicines Table 10.19 summarises the use of other medicines in bariatric surgery. Table 10.19  Miscellaneous agents in bariatric surgery. Medication Summary of evidence and considerations Antimuscarinics No data available on absorption after bariatric surgery Benzodiazepines43–46 Bioavailability probably unaffected, shorter time to peak concentration Lisdexamfetamine47 A single-­dose case–control study found no significant differences in lisdexamfetamine and active metabolite d-­amfetamine following RYGB compared to non-­surgical controls. Due to potential for inter­individual differences, monitor for adverse effects and loss of efficacy. Methadone48 Substantial increase in bioavailability after sleeve gastrectomy in one case report, possibly related increased rate of gastric emptying; consider plasma level and QT monitoring Methylphenidate49,50 Conflicting limited data; one case report of reduced treatment efficacy after RYGB that resolved after switching to transdermal patch suggesting reduced oral bioavailability; another reported signs of toxicity Modafinil No data available on absorption after bariatric surgery Orexin antagonists No data available on absorption after bariatric surgery Pregabalin17 Increased levels shortly after surgery and decreased values in the long term post-­surgery; monitor for adverse effects and loss of efficacy Solriamfetol No data available on absorption after bariatric surgery Zolpidem In an in vitro model found to have non-­significant lower dissolution after RYGB.32 Food delays the onset of effect; take on an empty stomach.51 RYGB, Roux-­en-­Y gastric bypass.