COMPREHENSIVE CARE CLINIC: DIABETES: Diabetic Peripheral Neuropathy: Prevention Is the Best Cure

Pharmacy Times, Volume 0,0

Diabetic neuropathies are a family of nerve disordersthat are a long-term complication of diabetes. Thehighest rates of neuropathy are found in peoplewho have poor glucose control and have had the disease formore than 25 years.1 Cigarette smoking, alcohol consumption,age, height, and high cholesterol levels also are independentrisk factors for neuropathy.2

Diabetic neuropathy affects sensory, autonomic, andmotor neurons. Every organ system in the body is vulnerableto damage. The lower extremities are most commonlyaffected. The heart, gastrointestinal tract, and genitourinarysystem are commonly affected as well, however.

Most health care providers can easily recognize diabeticperipheral neuropathy, which is characterized by symptomsranging from slight changes in sensation to the excruciatingpain associated with focal neuropathy. The disease developsslowly and begins with a painless loss or change of sensation.The pattern of neuropathy begins in fingers and toesand progresses to a "glove and stocking" distribution.3Patients may complain of burning, tingling, aching, numbness,sharp pain, or cold sensation. These painful symptomsoccur in a minority of patients (11%-32%).4 The majority ofpatients experience a progressive lack of ability to feel painor judge temperature. These problems can lead to limbamputation because of nonhealing foot ulcers.

Focal neuropathy appears suddenly and affects specificnerves, usually in the head, torso, or leg. It is very painfuland unpredictable. Yet, it usually improves by itself over aperiod of weeks or months and does not cause long-termdamage.

Treatment of neuropathy is notoriously difficult. Thereare 3 facets to treatment of diabetic neuropathy: primaryprevention, symptom management, and disease modification.Prevention of the disease is critical. Prevention can beaccomplished with optimal control of blood sugar and managementof modifiable risk factors such as smoking, weight,and hypertension. The Diabetes Control and ComplicationsTrial and the UK Prospective Diabetes Study demonstrated amarked reduction in neuropathic complications with tightglucose control.5,6

Treatments designed to control symptoms often turn intopolypharmacy nightmares and are only moderately effective.These medication regimens may include tricyclic antidepressants;tramadol; anticonvulsives such as gabapentin,carbamazepine, and lamotrigine; selective serotonin reuptakeinhibitors; bupropion; venlafaxine; and various narcotics.All of these agents have the potential for significantside effects and drug interactions.

Topical agents such as capsaicin cream and isosorbidedinitrate (ISDN) spray have been shown to be useful in painmanagement, although capsaicin cream must be used frequentlyand causes a burning sensation that may be intolerablein people who are already in pain. ISDN spray is notavailable in the United States.

OTC treatments such as NSAIDs have demonstrated efficacyin patients who rated their pain as "moderate." Thesedrugs must be used carefully, however, due to the possibilityof renal impairment in a population that is already at highrisk for this complication. They are not generally used asmonotherapy for diabetic neuropathy.

Complementary and alternative therapies also have beenstudied for peripheral neuropathy, with varying degrees ofsuccess. Electrostimulation, used transcutaneously or percutaneously,has had positive results in clinical trials. Yet, thetrials had very strict exclusion criteria, which prohibited alarge segment of the diabetic population from participating.7

Thioctic acid (also known as alpha-lipoic acid) has beenshown to be useful for short-term relief of neuropathy. Itrequires daily 30-minute intravenous infusions, however—which may limit its usefulness.1 Herbal manufacturers arepromoting this compound in oral preparations, but theseproducts are unlikely to be useful, given that the half-life ofthioctic acid is 2 to 4 minutes.

Carnitine supplementation proved beneficial in 2 recenttrials. Patients who took 1000 mg 3 times daily reported significantimprovement in pain after 52 weeks of treatment. Ittook a minimum of 26 weeks, however, to notice anyimprovement—which might lead patients to discontinuetherapy prior to an adequate trial.8

Primary prevention is the most important part of diabeticneuropathy treatment. This aim can be achieved by optimalglucose control and modification of other risk factors.

Dr. Garrett is a clinical pharmacist practitioner at Cornerstone HealthCare in High Point, NC.

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