there are more than 150,000 bariatric surgeries performed in the united states each year.1 ) about two - thirds of patients presenting for bariatric surgery have a history of some psychiatric disorder,2 ) and around 4.0% of bariatric candidates suffer from bipolar disorder.2,3 ) over one - third of patients who undergo bariatric surgery take some psychiatric medication.2,4 ) lithium continues to be used as a first - line treatment for bipolar disorder and , given its narrow therapeutic window , changes in lithium pharmacokinetics following bariatric surgery is of particular interest .
we report a case of lithium toxicity after sleeve gastrectomy that illustrates the potential need for closer monitoring of lithium levels following bariatric surgery .
the established association between morbid obesity and psychiatric disease2,3,5 ) makes understanding how bariatric surgery affects the pharmacokinetics of psychotropic drugs of utmost importance .
an 18-year - old female with a history of bipolar disorder , anxiety disorder , and bulimia nervosa , initially presented to the emergency department complaining of fatigue , diarrhea , and tremors .
the patient was taking 900 mg of lithium daily ( 300 mg morning , 600 mg evening ) .
she was also taking citalopram 30 mg once daily and ziprasidone 160 mg once daily .
the patient had lost 70 pounds since starting her bariatric surgery consultation program 6 months prior to presentation . since her surgery
, she had intermittent symptoms of vomiting and nausea , which contributed to poor fluid intake .
the patient was admitted for dehydration and acute kidney injury , and aggressive intravenous hydration was initiated .
lithium level was found to be 2.7 mmol / l , and lithium toxicity was diagnosed .
mmol / l , potassium 3.1 mmol / l , chloride 96 mmol / l , bicarbonate 20 mmol / l , blood urea nitrogen ( bun ) 53 mg / dl , creatinine ( cr ) 2.19 mg / dl and hemoglobin ( hb ) of 11.7 g / dl .
the patient s condition deteriorated dramatically on the second day of admission and she became very lethargic and obtunded . despite having received 5 l intravenous fluid , the lithium level remained elevated at 2.6 mmol / l ( bun 44 mg / dl and cr 1.50 mg / dl ) .
serum sodium , potassium , chloride and bicarbonate all normalized , while the hb level declined to 10.3 g / dl . on examination ,
two courses of hemodialysis were subsequently performed , and by the third day of her admission her serum lithium was 1.4
she continued to exhibit agitation , restlessness , and confusion with inability to follow 1-step commands .
chest and abdominal computed tomography ( ct ) scan showed no significant pathology ; head ct showed no evidence of bleeding or stroke .
hospital course was further complicated by thyroid storm , nephrogenic diabetes insipidus , and pneumonia .
the patient was discharged 19 days after admission at which time no neurologic sequelae were noted .
although not well studied , concerns over alterations in the pharmacokinetics of lithium following bariatric surgery have been documented in the literature .
notably , there have been two cases of lithium toxicity following roux - en - y gastric bypass.6,7 ) the mechanism behind our patient s lithium toxicity is likely multifactorial .
the patient had acute kidney injury , as evidenced by her increased creatinine , as well as likely secondary decreased fluid intake and dehydration .
one study found the incidence of acute kidney injury in individuals who underwent bariatric surgery to be 5.8%.8 ) given that lithium is primarily renally excreted , it is clear that an alteration in hydration status affecting kidney function would lead to decreased lithium clearance .
dehydration occurs frequently during the six months following bariatric surgery , owing to the mechanically restricted stomach limiting fluid intake .
additionally , weight loss itself can contribute to changes in the pharmacokinetics of lithium . in one study , the clearance of lithium in obese individuals was found to be significantly greater than that of a control group ( 33.97.0 ml / min versus 23.06.2 ml / min ; p=0.005).9 ) the 31.75 kg weight loss our patient experienced in just a few months may have impaired her lithium clearance . furthermore , the possibility of increased lithium absorption after bariatric surgery has been raised previously in the literature . in one in vitro model , investigators studied the dissolution of psychotropic drugs in media environments that mimic the gastrointestinal tract of a post - roux - en - y patient and compared to that of a preoperative patient . while most of the drugs studied were found to have decreased or unaffected dissolution , the dissolution of lithium increased significantly ( > 200% ) in the post bariatric surgery model.10 ) stomach ph increases significantly following both roux - en - y and vertical sleeve gastrectomy,11 ) which may facilitate the deprotonation of carbonate salt and result in an increased dissolution of lithium ions . given its narrow therapeutic window ,
careful monitoring and perhaps dose reductions may be necessary for patients during the pre- and postoperative period .
although some institutions have protocols in place to monitor lithium levels before and after bariatric surgery,12 ) there are currently no widely accepted guidelines .
a significant gap still exists in the literature concerning the pharmacokinetics of psychotropic medications following bariatric surgery .
further research on the pharmacokinetic changes of high - risk medications like lithium following bariatric surgery seems needed .
 we are presenting the first documented case of lithium toxicity after vertical sleeve gastrectomy surgery in an 18 year - old female with psychiatric history of bipolar disorder who was treated with lithium . 
 this case illustrates the need for closer monitoring of lithium levels following bariatric surgery . 
 both psychiatrists and surgeons should be aware of the potential risk of lithium toxicity following bariatric surgery , as well as the need to judiciously monitor lithium level and possibly adjust the dose of some medications . 
INTRODUCTION
CASE
DISCUSSION