A 45-year-old female, known case of Irritable bowel syndrome presented with a poorly localized pain especially involving the axial skeleton. The pain was severe, associated with tenderness, and had been occurring for the past 4 months. She also repoed fatigue, stiffness, sleep disturbance, cognitive dysfunction, anxiety, and depression. Lab and radiographic studies were normal and didn’t reveal any abnormalities. All of the following drugs are approved for the above condition EXCEPT: –

**Core Concept**
The patient's symptoms are consistent with fibromyalgia, a chronic condition characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and cognitive dysfunction. Fibromyalgia is a complex disorder involving multiple neurotransmitter systems, including serotonin, dopamine, and substance P, which contribute to the development of pain and other symptoms.

**Why the Correct Answer is Right**
The patient's symptoms and lack of abnormalities on lab and radiographic studies are consistent with fibromyalgia. Fibromyalgia is diagnosed based on clinical criteria, including widespread pain index (WPI) and symptom severity scale (SSS). The treatment of fibromyalgia typically involves a combination of pharmacological and non-pharmacological interventions, including medications that target the serotonin and dopamine systems. **Option C** is correct because the medications listed below it are all approved for the treatment of fibromyalgia.

**Why Each Wrong Option is Incorrect**
**Option A:** Duloxetine is a serotonin-norepinephrine reuptake inhibitor (SNRI) that is approved for the treatment of fibromyalgia. It works by increasing the levels of serotonin and norepinephrine in the brain, which helps to reduce pain and other symptoms.

**Option B:** Milnacipran is another SNRI that is approved for the treatment of fibromyalgia. It also works by increasing the levels of serotonin and norepinephrine in the brain.

**Option D:** Pregabalin is an anticonvulsant medication that is approved for the treatment of fibromyalgia. It works by reducing the release of excitatory neurotransmitters, such as substance P, which contributes to the development of pain.

**Clinical Pearl / High-Yield Fact**
It's worth noting that fibromyalgia is often underdiagnosed and undertreated. A high index of suspicion is necessary to diagnose fibromyalgia, and a multidisciplinary approach to treatment is often the most effective way to manage symptoms.

**Correct Answer:** A.

✓ Correct Answer: D. Tetrabenazine