Q150) A 34 year old male nurse is brought to the Emergency Room by the EMS with altered mental status. As per his sister, the patient has been on Lithium for his manic symptoms for the past one year. However, his psychiatrist added Fluoxetine and Amitriptyline about 1 week ago for history of depression symptoms.
On physical examination, he has low grade fever at 100.5F, Blood pressure of 110/82 and Heart rate of 120/min. He is confused and the pupils are dilated. There is rigidity in extremities and deep tendon reflexes are exaggerated. Complete blood count, creatinine and Creatine kinase level are within normal limits. Most likely diagnosis:
A) Neuroleptic Malignant Syndrome
B) Lithium Toxicity
C) Serotonin Syndrome
D) Amphetamine abuse
E) Cocaine Intoxication
Archer USMLE Step 3 Blog 
B,Lithium toxicity,In NMS increased CK, serotonin synd occurs with combination of SSRI and Mao
c?
c
B) Lithium Toxicity
B
LITHIUM CAUSES TREMORS AND BODY JERKS BUT NOT MYDRIASIS WHAT ABOUT OPTION D
AMPHETAMINES CAUSE MYDRIASIS, TACHYCARDIA , DISORIENTATION, STROKE LIKE SYMPTOMS
C. Serotonin syndrome
Examination findings can include: hyperthermia, agitation, ocular clonus, tremor, akathisia, deep tendon hyperreflexia, inducible or spontaneous clonus, muscle rigidity,DILATED PUPILS, dry mucus membranes, increased bowel sounds, flushed skin, and diaphoresis. Neuromuscular findings are typically more pronounced in the lower extremities.
Patient is taking 3 drugs which can potentiate/precipitate serotonin.
Lithium increases senstivity of postsynaptic receptors.
TCA inhibit both NE & Serotonin uptake
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I completely agree with Wildoit on this one. There’s no history of amphetamine or cocaine abuse, so that’s out. Moreover, there’s no hypertension which is key. This is not NMS as it gives you an extremely high temperature and renal involvement. lithium toxicity will affect the kidney’s as well and the creatinine levels are normal here. There’s no interaction with Amitriptyline because anticholinergic activity might be seen.
The problem here is lithium’s interaction with Prozac and this causes serotonin syndrome. Mild symptoms may only consist of increased heart rate, shivering, sweating, dilated pupils, myoclonus (intermittent tremor or twitching), as well as overresponsive reflexes. Moderate intoxication includes additional abnormalities such as hyperactive bowel sounds, high blood pressure and hyperthermia; a temperature as high as 40 °C (104 °F) is common in moderate intoxication. The overactive reflexes and clonus in moderate cases may be greater in the lower limbs than in the upper limbs.
Extremely close to NMS but in NMS there’s something you don’t want to forget and that is elevated CPK which is normal in this case.
mnemonic for NMS: FALTER
F – Fever
A – Autonomic instability
L – Leukocytosis
T – Tremor
E – Elevated enzymes (elevated CPK)
R – Rigidity of muscles
Answer: Serotonin syndrome!
C. From Wiki: “Symptom onset in [serotonin toxicity/syndrome] is usually rapid, often occurring within minutes. Serotonin syndrome encompasses a wide range of clinical findings. Mild symptoms may only consist of increased heart rate, shivering, sweating, dilated pupils, myoclonus (intermittent tremor or twitching), as well as overresponsive reflexes.[1] Moderate intoxication includes additional abnormalities such as hyperactive bowel sounds, high blood pressure and hyperthermia; a temperature as high as 40 °C (104 °F) is common in moderate intoxication. The overactive reflexes and clonus in moderate cases may be greater in the lower limbs than in the upper limbs. Mental status changes include hypervigilance and agitation.”
lithium and fluoxetine is bad combo and leads to serotonin syndrome
its not nms as ck is normal and no leucocystosis