A 73-year-old man with bipolar disorder is brought to the emergency department by his daughter, who has been visiting him for several days. She reports that "he's not himself." The patient has become increasingly confused, which is not typical for him. He has bilateral hand tremors, has difficulty walking straight, and has vomited over the past few days. Two weeks ago, he saw his new primary care physician, who added hydrochlorothiazide to the patient's medication regimen. The patient has been psychiatrically stable for many years and has been seeing a psychiatrist, who has prescribed mood stabilizers and antipsychotics. He has no history of alcohol or substance use disorders. His daughter does not know which psychiatric medications he takes. Temperature is 37.2 C (99 F), blood pressure is 130/80 mm Hg, pulse is 65/min, and respirations are 16/min. The patient's pulse oximetry shows 93% on room air. He is disoriented and ataxic. As he is being assessed, he has a generalized seizure that lasts 2-3 minutes. Which of the following medications is the most likely cause of this patient's symptoms?

Question

A 73-year-old man with bipolar disorder is brought to the emergency department by his daughter, who has been visiting him for several days.  She reports that "he's not himself."  The patient has become increasingly confused, which is not typical for him.  He has bilateral hand tremors, has difficulty walking straight, and has vomited over the past few days.  Two weeks ago, he saw his new primary care physician, who added hydrochlorothiazide to the patient's medication regimen.  The patient has been psychiatrically stable for many years and has been seeing a psychiatrist, who has prescribed mood stabilizers and antipsychotics.  He has no history of alcohol or substance use disorders.  His daughter does not know which psychiatric medications he takes.  Temperature is 37.2 C (99 F), blood pressure is 130/80 mm Hg, pulse is 65/min, and respirations are 16/min.  The patient's pulse oximetry shows 93% on room air.  He is disoriented and ataxic.  As he is being assessed, he has a generalized seizure that lasts 2-3 minutes.  Which of the following medications is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d7d1_7cda_bc81_757924ed0a0b_MD0003_00 This patient is exhibiting signs and symptoms of lithium toxicity. These may include new onset of severe gastrointestinal symptoms, confusion, ataxia, tremor, and other signs of neuromuscular irritability such as fasciculations and seizures. This patient was previously stable on his psychiatric medications; therefore, the recent addition of hydrochlorothiazide is likely responsible for increasing his lithium serum level. Thiazide diuretics can cause a decrease in the renal clearance of lithium and lead to lithium toxicity. The risk of lithium toxicity is higher in patients with dehydration from any cause (eg, vomiting, diarrhea, fever, diuresis) and in elderly patients due to a lower glomerular filtration rate and reduced volume of distribution. Other medications that can increase lithium levels include ACE inhibitors, nonsteroidal anti-inflammatory drugs, tetracyclines, and metronidazole. (Choices A, B, and E) Bupropion is a dopamine and norepinephrine reuptake inhibitor used as an antidepressant and as an aid for smoking cessation. The antipsychotics haloperidol and risperidone are dopamine antagonists used to treat psychosis or as adjuncts to mood stabilizers in the treatment of bipolar disorder. Although bupropion, haloperidol, and risperidone can increase neuromuscular irritability and the risk of seizures, none are typically associated with this patient's other presenting symptoms. (Choices C and F) Lamotrigine and valproic acid are anticonvulsants that are also used in the treatment of bipolar disorder. Lamotrigine is associated with Stevens-Johnson syndrome. Valproic acid may cause gastrointestinal symptoms, hepatitis, pancreatitis, and hepatic encephalopathy. Both medications would decrease rather than increase the risk of seizures. Educational objective: Concurrent use of thiazide diuretics-as well as ACE inhibitors, tetracyclines, metronidazole, and nonsteroidal anti-inflammatory drugs-and lithium can increase serum lithium levels and lead to symptoms of lithium toxicity, including gastrointestinal symptoms, confusion, ataxia, tremor, and seizures. References: Drug interactions with lithium: an update. (http://www.ncbi.nlm.nih.gov/pubmed/26936045) Drug-related admissions due to interaction with an old drug, lithium. (http://www.ncbi.nlm.nih.gov/pubmed/24579242)

A 73-Year-Old Man with Bipolar Disorder Is Brought to the Emergency