A 28-year-old male with a history of chronic DNP (2,4-dinitrophenol) abuse for weight loss presents with progressive weakness, paresthesias in both feet, and a core temperature of 39.2°C despite ambient temperature of 22°C. He reports taking DNP capsules irregularly over the past 6 months. Neurological examination reveals distal sensory loss and diminished ankle reflexes. What is the most appropriate immediate next step in management?

Explanation

## Management of Chronic DNP Uncoupler Toxicity ### Pathophysiology of DNP **Key Point:** DNP is a lipophilic weak acid that freely crosses the inner mitochondrial membrane. It accepts a proton in the matrix (where pH is low) and releases it in the intermembrane space (where pH is high), thereby dissipating the proton gradient without ATP synthesis. This uncoupling causes: - Uncontrolled heat generation (hyperthermia) - Severe metabolic derangement - Chronic peripheral neuropathy (distal, sensorimotor, dose- and duration-dependent) ### Clinical Features of Chronic DNP Toxicity | Feature | Acute | Chronic | |---------|-------|----------| | **Hyperthermia** | Severe, acute onset | Persistent, refractory | | **Sweating** | Profuse | Chronic diaphoresis | | **Neuropathy** | Absent | Distal sensorimotor, irreversible | | **Weight loss** | Rapid | Progressive | | **Mechanism** | Acute uncoupling | Chronic mitochondrial damage + axonal degeneration | ### Immediate Management Algorithm ```mermaid flowchart TD A[Chronic DNP Toxicity Presentation]:::outcome --> B[STOP DNP immediately]:::urgent B --> C[Initiate Cooling Measures]:::action C --> D[Admit for ICU/HDU Monitoring]:::action D --> E[Monitor Vital Signs, Core Temperature]:::action E --> F[Check Serum Electrolytes, CK, Myoglobin]:::action F --> G[IV Hydration + Urine Alkalinization if CK elevated]:::action G --> H[Supportive Care: Manage Neuropathy Symptoms]:::action H --> I[Counsel on Irreversibility of Nerve Damage]:::outcome ``` **High-Yield:** The **immediate priority in chronic DNP toxicity is cessation of the drug and aggressive cooling**, combined with close monitoring for rhabdomyolysis and acute kidney injury. There is no antidote; management is entirely supportive. ### Why NOT Thiamine (Option A)? **Warning:** While thiamine deficiency can cause peripheral neuropathy (Wernicke–Korsakoff syndrome), this patient's neuropathy is **DNP-induced** (from chronic uncoupling and mitochondrial damage), not nutritional. Thiamine supplementation, though not harmful, is not the primary intervention and delays the critical step of drug cessation and cooling. ### Why NOT EMG/NCS First (Option C)? **Clinical Pearl:** EMG/NCS findings (distal axonal sensorimotor neuropathy) will confirm the diagnosis, but this is a **confirmatory test, not a management priority**. The clinical picture is already diagnostic of DNP toxicity. Performing EMG/NCS delays urgent cooling and monitoring, which can be life-threatening in acute uncoupler crisis. ### Why NOT Corticosteroids (Option D)? **Warning:** Corticosteroids have no role in DNP neuropathy. The neuropathy is caused by **chronic axonal degeneration from mitochondrial uncoupling**, not inflammation. Moreover, corticosteroids can worsen hyperglycemia and increase infection risk in a critically ill patient. The neuropathy is largely **irreversible** once established; steroids will not halt progression. ### Correct Approach: Cessation + Cooling + Monitoring (Option B) 1. **Immediate cessation of DNP** — no tapering; abrupt discontinuation is necessary 2. **Aggressive cooling:** Ice packs, cooling blankets, cold IV fluids; target core temperature < 38°C 3. **ICU/HDU admission** for continuous monitoring 4. **Investigations:** - Serum electrolytes (K^+^, Na^+^, Mg^2+^) - Creatine kinase (CK) and myoglobin (risk of rhabdomyolysis) - Arterial blood gas (monitor for acidosis) - Renal function (AKI risk) 5. **Supportive care:** - IV hydration (target urine output 200–300 mL/h if CK elevated) - Urine alkalinization (sodium bicarbonate) if myoglobinuria present - Symptomatic management of neuropathy (gabapentin, pregabalin for pain) 6. **Counseling:** Inform patient that the neuropathy is **largely irreversible** and may progress even after DNP cessation **High-Yield:** DNP-induced neuropathy is a **dose- and duration-dependent axonal degeneration** that does not respond to anti-inflammatory agents. Early recognition and cessation can prevent further deterioration, but existing nerve damage is permanent. [cite:Harrison 21e Ch 476; Robbins 10e Ch 27]