Why was escitalopram (Selective Serotonin Reuptake Inhibitor) stopped and duloxetine (Serotonin-Norepinephrine Reuptake Inhibitor) started in a patient with profound intellectual disabilities, intermittent explosive disorder, premenstrual dysphoric disorder, and anxiety disorder, who presented with tremor?

Duloxetine Was Substituted for Escitalopram to Manage Tremor

The neurologist recommended switching from escitalopram to duloxetine because escitalopram can cause or exacerbate tremor, while duloxetine may be more beneficial for both the patient's anxiety and tremor symptoms.

Relationship Between SSRIs and Tremor

• Tremor is one of the most common neurological adverse effects of Selective Serotonin Reuptake Inhibitors (SSRIs) like escitalopram 1, 2
• Escitalopram has been documented to cause or exacerbate movement disorders, including tremor and even Parkinsonism in some cases 3, 4
• SSRIs can cause tremor through serotonergically mediated inhibition of the dopaminergic system 2, 3
• About 63% of patients receiving second-generation antidepressants (including SSRIs) experience at least one adverse effect, with tremor being commonly reported 1

Benefits of Switching to Duloxetine (SNRI)

• Duloxetine, a Serotonin-Norepinephrine Reuptake Inhibitor (SNRI), has a different mechanism of action that may be less likely to cause or worsen tremor due to its noradrenergic effects 1
• SNRIs like duloxetine are effective for anxiety disorders, which is relevant for this patient with an anxiety disorder diagnosis 1
• Duloxetine has demonstrated efficacy in treating neuropathic pain conditions, which may be beneficial if the tremor has a neuropathic component 1
• The gradual titration schedule (20 mg → 40 mg → 60 mg → 120 mg) allows for monitoring of tolerability and effectiveness 5

Considerations for This Specific Patient

• The patient has multiple psychiatric diagnoses (profound intellectual disabilities, intermittent explosive disorder, premenstrual dysphoric disorder, and anxiety disorder) that require careful medication management 1
• The high dose of escitalopram (30 mg) being used exceeds typical recommended doses and may have increased the risk of adverse effects including tremor 6
• The patient is already on multiple psychotropic medications (lurasidone, olanzapine, diazepam), increasing the risk of drug interactions and side effects 1
• Patients with intellectual disabilities may be more sensitive to medication side effects and may have difficulty reporting symptoms 1

Potential Risks and Monitoring Needed

• Duloxetine can cause its own side effects, including nausea, dizziness, somnolence, and dry mouth 5
• SNRIs have been associated with increased blood pressure and pulse, requiring monitoring in this patient 1
• Risk of serotonin syndrome when switching between serotonergic medications necessitates the gradual cross-titration approach the neurologist prescribed 1, 6
• Both medications carry risks of discontinuation syndrome, explaining the slow taper off escitalopram while gradually introducing duloxetine 1, 5

Important Caveats and Precautions

• The switch should be closely monitored as duloxetine has its own potential adverse effects, including nausea (most common reason for discontinuation), increased blood pressure, and hepatic effects 1, 5
• Coordination between the neurologist and psychiatrist is essential since the patient is described as "relatively stable" on the current psychiatric medication regimen 1
• The high target dose of duloxetine (120 mg) is at the upper end of the therapeutic range and should be carefully evaluated for tolerability and efficacy 5
• If tremor persists or worsens on duloxetine, further neurological evaluation may be needed to rule out other causes of tremor 1