Neuropathy secondary to drugs

Definition

Neuropathy secondary to drugs is a condition where there is a loss of sensation (or movement) in a part of the body. It is associated with use of a medication that can damage nerves.

Causes, incidence, and risk factors

The damage is caused by toxic effects of certain medications on the peripheral nerves (the nerves not in the brain or spinal cord). There is usually evidence of damage to the axon part of the nerve cell, which blocks conduction of the nerve impulse through the cell.

Most commonly, there is involvement of multiple nerves (polyneuropathy) which usually appears as sensation changes that begin in outward areas of the body (distal) and progress toward the center of the body (proximal). Occasionally, there may also be changes in movement.

Many medications can be associated with the development of neuropathy, including:

• Heart or blood pressure medications
  o Amiodarone
  o Hydralazine
  o Perhexiline
  
• Drugs used to fight cancer
  o Vincristine
  o Cisplatin
  
• Drugs used to fight infections
  o Metronidazole (Flagyl)
  o Nitrofurantoin
  o Thalidomide (used to fight leprosy)
  o INH (isoniazid) - used against tuberculosis
  
• Drugs used to treat skin conditions (Dapsone)
  
• Anticonvulsants (Phenytoin)
  
• Anti-alcohol drugs (Disulfiram)
  

Symptoms

• Numbness, loss of sensation
  
• Tingling, abnormal sensations
  
• Sensation changes usually begin in the feet or hands and progress inward
  

Signs and tests
A neurological examination may show abnormalities. Blood levels of the medication may show toxic levels. Normal blood levels of certain drugs may be toxic in elderly or other highly susceptible persons.

Treatment

Treatment is based on the symptoms and their severity.

Medications may be used to control painful neuropathy. However, the use of medications is usually discouraged unless absolutely necessary. Over-the-counter analgesics may be helpful for mild pain. Narcotic analgesics, such as codeine, may be needed to control severe pain. Antidepressant medications, or anticonvulsants (such as carbamazepine or phenytoin), may be helpful for some types of nerve pain.