This was a case I came across recently where duloxetine was added to a patient’s regimen. The provider did not adequately assess the medication and recognize that the patient was already taking an SNRI in Effexor. This led to a case of duplicate SNRI therapy. Here’s the case:
Linda M., a 58-year-old female, has the following background info;
Past Medical History:
- Major depressive disorder
- Generalized anxiety disorder
- Diabetic peripheral neuropathy
- Hypertension
- Osteoarthritis
- Insomnia
Allergies:
- NKDA
Current Medication List:
- Venlafaxine XR 150 mg PO daily (for depression/anxiety; stable for 3 years)
- Duloxetine 30 mg PO daily (started 2 weeks ago for neuropathic pain)
- Metformin 1000 mg PO BID
- Lisinopril 20 mg PO daily
- Hydrochlorothiazide 25 mg PO daily
- Acetaminophen 1000 mg PO TID PRN pain
- Gabapentin 300 mg PO TID
- Trazodone 50 mg PO at bedtime
- Atorvastatin 40 mg PO nightly
Recent Clinical Encounter:
Linda was seen by her primary care provider for worsening burning pain in her feet related to diabetic neuropathy. Duloxetine 30 mg daily was initiated for neuropathic pain management. Her existing venlafaxine XR therapy was not adjusted or discontinued.
Current Symptoms (2 weeks later):
- Increased sweating
- Restlessness and mild tremor
- Nausea
- Headache
- Blood pressure elevated at 156/92 mmHg (previously well controlled)
Assessment:
The patient is receiving duplicate SNRI therapy (venlafaxine + duloxetine). Both medications increase serotonin and norepinephrine levels, placing the patient at increased risk for serotonin toxicity, hypertension, and additive adverse effects without clear additional benefit.
Drug Therapy Problem Identified:
- Unnecessary duplicate SNRI therapy: Two SNRIs prescribed concurrently
- Safety concern: Increased risk of serotonin syndrome and blood pressure elevation
Recommended Intervention:
- Discontinue one SNRI (most commonly taper and discontinue venlafaxine if duloxetine is preferred for neuropathic pain); I would have likely initially reduced the venlafaxine XR to 75 mg daily when duloxetine was started. Recall that venlafaxine is one of the worst antidepressants as far as withdrawal symptoms when reducing or discontinuing (excellent board exam nugget)
- Monitor blood pressure and symptoms
- Educate patient on signs of serotonin syndrome
Teaching Pearl:
When adding medications for comorbid conditions (e.g., neuropathic pain), always reassess existing therapy to avoid therapeutic duplication, especially within the same pharmacologic class.
0 Comments