(718) Can Interaction Between Phenelzine and Olanzapine Trigger Neuroleptic Malignant Syndrome?

Introduction: Neuroleptic Malignant Syndrome(NMS) is a life threatening acute condition associated with the use of neuroleptic medications. Though rare, a few cases were reported of NMS developing as an adverse reaction after small doses of low potency 2nd gen antipsychotics. Early recognition and treatment are crucial. While the classic presentation after use of typical antipsychotics is well-documented, this report describes a case of NMS who was on phenelzine at home and was given Olanzapine inpatient leading to NMS.

Description: Patient is a 88y/o M with PMH of dementia presented with altered mental status and visual hallucinations. Pt was afebrile, vitals were stable other than mild tachycardia. Labs revealed Cr 1.96, WBC 9 and lactate of 3.96. Although no obvious source of infection, pt was treated for presumed sepsis with IV Abx. Given the pt's acute agitation he was given Zyprexa after which he was noted to have severe intermittent tremors but was withdrawing to painful stimuli, inconsistent with seizures. VBG revealed pH of 7.1,lactate 11.3 with rectal temps of 108 F and increased neck/ upper extremity rigidity. Given concern for NMS, rapid cooling was initiated and Dantrolene was given with significant improvement. EEG showed generalized background slowing and absence of alpha waves. CSF analysis revealed normal cell counts/glucose,protein, negative viral/bacterial/fungal CSF cultures. MRI brain was negative for infarct/hemorrhage/mass. However, given the delay of tx, pt's course was complicated by acute kidney failure necessitating dialysis and his clinical status deteriorated. Per pt goals of care discussed with family, he was placed on hospice care.

Discussion: Although NMS is more commonly reported with higher/longer doses of antipsychotics, it is not entirely impossible for it to develop after a single dose, especially in a patient already on an MAO inhibitor. ⁤⁤While serotonin syndrome is an acknowledged risk, NMS could theoretically occur due to alterations in dopamine metabolism or other complex interactions. The acute onset of symptoms on the administration of Olanzapine suggests that the medication may have played a pivotal role in triggering NMS. The case, therefore, illustrates a need for continued vigilance and assessment of patients who are prescribed MAOI and antipsychotics.