Diabetic Neuropathy

See Also

Epidemiology

Occurs in Type I and Type II Diabetes Mellitus
Occurs in 42% of Type II Diabetes Mellitus
1. Onset within 10 years of disease
2. Higher risk with higher Glycosylated Hemoglobin
3. Partanen (1995) N Engl J Med 333:89-94 [PubMed]

Types

Diagnosis

See also Peripheral Neuropathy Testing

Differential Diagnosis

See Leg Pain
See Autonomic Neuropathy
Peripheral Polyneuropathy
1. Vitamin B12 Deficiency
  1. Especially when using Metformin
2. Folic Acid Deficiency
3. Iron Deficiency Anemia
4. Hypothyroidism
5. Uremia
6. Chemical Toxin exposure (heavy metal toxicity)
7. Alcohol Abuse
8. Sarcoidosis
9. Leprosy
10. Periarteritis nodosum
11. Systemic Lupus Erythematosus
12. Leukemia
Other important causes of Leg Pain
1. Lumbar Disc Disease with radiculopathy
2. Lumbar central spinal stenosis
3. Claudication
4. Night Cramps
5. Restless Leg Syndrome
6. Degenerative Joint Disease
  1. Hip Osteoarthritis
  2. Knee Osteoarthritis
  3. Ankle Osteoarthritis

Complications (of distal symmetric Polyneuropathy)

See Charcot Foot
See Foot Wound
See Suspected Osteomyelitis in Diabetes Mellitus
See Peripheral Neuropathy Tremor

Management
Approach

See dosing regimens in next section
Step 1
1. See prevention below for diabetes care optimization including glycemic control
2. Set realistic patient expectations (e.g. 30-50% symptom improvement with medications)
3. Evaluate for other causes of Peripheral Neuropathy (see differential diagnosis above)
Step 2
1. Tricyclic Antidepressants (e.g. Amitriptyline, Nortriptyline, Desipramine): NNT 2-4
Step 3
1. Anticonvulsants (e.g. Gabapentin, Pregabalin): NNT 3-8
Step 4
1. Serotonin-Norepinephrine reuptake inhibitors (e.g. Duloxetine, Venlafaxine): NNT 4-11
Step 5
1. Reconsider differential diagnosis
2. Chronic Analgesics (Opioids, Tramadol)
3. Consider SSRI (e.g. Escitalopram), although lack of adequate studies to support use
4. Consider pain management referral
Adjuncts (add at any point)
1. Topical Lidocaine (Lidoderm 5% patch) or the OTC, less expensive Lidocare 4% patch (but still expensive!)
2. Capsaicin 0.075% cream (often intolerable due to burning)
3. Transcutaneous electrical nerve stimulation (TENS)
4. Isosorbide Dinitrate spray 30 mg applied to bottom of feet at bedtime
5. Acupuncture (no large, high quality studies in Diabetic Neuropathy to support use)

Management
Medications for Painful Peripheral Neuropathy

Tricyclic Antidepressants
1. May be more effective in burning, steady pain
2. Avoid in the elderly due to strong Anticholinergic effects (see Beers List)
3. Amitriptyline (Elavil) or Nortriptyline (Pamelor)
  1. Started at 10-30 mg at bedtime
  2. Increase to 50-75 mg (maximum 150 mg) at bedtime
4. Desipramine (Norpramin) starting at 25 mg at bedtime
Anticonvulsants
1. May be more effective in sharp lancinating pain
2. Gabapentin (Neurontin)
  1. Adjust for renal dysfunction
  2. Start at 100 mg at bedtime to 100 mg orally three time daily
  3. Advance to 300 orally three times daily (maximum 1200 mg three times daily)
3. Pregabalin (Lyrica)
  1. Very similar to Gabapentin, but no generic yet available and expensive
  2. More convenient dosing (twice daily), and no Renal Dosing adjustment as contrasted with Gabapentin
  3. Start at 50 mg orally two to three times daily
  4. Titrate to 100 mg orally three times daily or 150 mg twice daily (maximum 300 mg twice daily)
4. Other agents
  1. Other anticonvulsants (including Carbamazepine, Topiramate) do not have adequate evidence to support use
Serotonin-Norepinephrine Reuptake Inhibitors
1. Duloxetine (Cymbalta)
  1. Start at 20 mg twice daily
  2. Advance to 60 mg daily (or divided 30 mg twice daily)
2. Venlafaxine (Effexor)
  1. Extended release (preferred): Venlafaxine XR 37.5 mg daily (titrate to 225 mg daily)
  2. Regular (generic): Venlafaxine 37.5 mg twice daily (titrate to 225 mg divided twice daily)
Topical pain management
1. TENS Unit
2. Lidocaine 5% patch (Lidoderm) up to 3 patches applied daily to affected area (applied for no more than 12 hours daily)
3. Capsaicin 0.075% cream applied to affected area twice daily (start with small amount and slowly increase)
4. Isosorbide Dinitrate spray 30 mg applied to bottom of feet at bedtime
Analgesics
1. NSAIDS are not typically recommended in Diabetes Mellitus
  1. Risk of renal, gastrointestinal and cardiovascular risks
2. Tramadol (Ultram)
  1. See Tramadol for precautions (lower efficacy with adverse effect risk)
3. Opioids (avoid unless no other option available)

Prevention

See Diabetic Foot Care
Optimize Diabetes Mellitus management (Hemoglobin A1C <7-8%)
Optimize Hypertension and Hyperlipidemia Management

References