A 52-year-old man with a history of schizoaffective disorder is admitted to the hospital for treatment of a lower extremity cellulitis. The patient does not appear to have any other acute medical illness. He is continued on his home medications-lithium, risperidone, and sertraline-and cephalosporin therapy is initiated to treat his infection. During the hospital stay, the patient also receives ibuprofen and acetaminophen for pain and lorazepam as needed for anxiety and insomnia. His infection improves over the next 10-14 days, but prior to discharge, he develops repeated episodes of vomiting and diarrhea. At the same time, the patient becomes tremulous and uncoordinated, which makes it difficult for him to walk without falling. In addition, he seems confused. Vital signs are normal. Physical examination shows fasciculations and bilateral tremor. Which of the following medications is most likely to have caused this patient's new symptoms?

Question

A 52-year-old man with a history of schizoaffective disorder is admitted to the hospital for treatment of a lower extremity cellulitis.  The patient does not appear to have any other acute medical illness.  He is continued on his home medications-lithium, risperidone, and sertraline-and cephalosporin therapy is initiated to treat his infection.  During the hospital stay, the patient also receives ibuprofen and acetaminophen for pain and lorazepam as needed for anxiety and insomnia.  His infection improves over the next 10-14 days, but prior to discharge, he develops repeated episodes of vomiting and diarrhea.  At the same time, the patient becomes tremulous and uncoordinated, which makes it difficult for him to walk without falling.  In addition, he seems confused.  Vital signs are normal.  Physical examination shows fasciculations and bilateral tremor.  Which of the following medications is most likely to have caused this patient's new symptoms?

Quizplus · Accepted Answer

11ec25c8_d5d8_1da3_bc81_f1fab2e945a8_MD0003_00 The new onset of severe gastrointestinal symptoms, confusion, ataxia, and tremor (and other symptoms of neuromuscular irritability) in a patient taking lithium suggests lithium toxicity. Lithium is a mood stabilizer used to treat bipolar disorder and schizoaffective disorder (bipolar type). It has a narrow therapeutic index and relies on adequate kidney function for its excretion. This patient likely developed lithium toxicity due to a drug interaction with ibuprofen. Concurrent use of nonsteroidal anti-inflammatory drugs (eg, ibuprofen) can cause a decrease in renal clearance of lithium and lead to elevated serum lithium levels and lithium toxicity. Other drugs that increase lithium levels include thiazide diuretics, ACE inhibitors, tetracyclines, and metronidazole. (Choice A) Acetaminophen may cause gastrointestinal symptoms and hepatic toxicity. However, it is not likely to cause adverse neurological effects such as ataxia, fasciculations, or tremor. (Choice C) Lorazepam toxicity may cause sedation, confusion, and gait disturbance. However, it would not lead to fasciculations and bilateral tremor. Alternatively, lorazepam withdrawal is unlikely to occur after 10-14 days of as-needed use. (Choice D) Risperidone, a second-generation antipsychotic, may cause galactorrhea, orthostasis, metabolic syndrome, and extrapyramidal symptoms. Gastrointestinal symptoms are unlikely. In rare cases, risperidone can cause neuroleptic malignant syndrome, characterized by autonomic instability, high fevers, delirium, and muscle rigidity. (Choice E) Sertraline, a selective serotonin reuptake inhibitor, may cause gastrointestinal symptoms, fasciculations, and tremor. However, it is unlikely to lead to confusion or ataxia in therapeutic doses. If combined with other serotonergic drugs, it can lead to serotonin syndrome, which is characterized by mental status changes, autonomic instability, hyperthermia, and neuromuscular irritability. Educational objective: The addition of nonsteroidal anti-inflammatory drugs (or thiazide diuretics, ACE inhibitors, tetracyclines, and metronidazole) to lithium can increase serum lithium levels and lead to symptoms of toxicity, including gastrointestinal symptoms, confusion, ataxia, and tremor. 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 52-Year-Old Man with a History of Schizoaffective Disorder Is