Polyneuropathies caused by drugs

1. Big picture

Drug-induced polyneuropathy is an acquired toxic polyneuropathy caused by medications that damage peripheral nerves. In the exam, it belongs to the broader group of subacute sensory or sensorimotor polyneuropathies, together with toxic chemicals, vitamin deficiencies, uremia, vasculitis, sarcoidosis, and critical illness polyneuropathy.

The most important idea is simple:

A patient develops distal, symmetric numbness, burning pain, tingling, reduced ankle reflexes, and sometimes weakness after starting or accumulating a neurotoxic drug.

The lecture specifically lists vincristine, isoniazid, and nitrofurantoin as drug causes. For clinical practice and oral exam reasoning, also remember common modern neurotoxic drugs such as platinum chemotherapy, taxanes, bortezomib, thalidomide, metronidazole, linezolid, amiodarone, and some antiretrovirals.

The examiner usually wants you to recognize:

• the stocking–glove pattern,

• the temporal relationship to medication exposure,

• the difference between toxic axonal neuropathy and immune/inflammatory neuropathy,

• and the main management principle: stop, reduce, or replace the offending drug when possible.