Choosing Medications For Painful Diabetic Neuropathy

Author(s): 
By Matt Rampetsreiter, DPM, and Raymond Abdo, DPM

When using gabapentin, you should initiate treatment with a test dose of 100 mg for elderly patients and gradually increase the dosage by 100 to 300 mg every three to five days. The median effective daily dose ranges between 900 to 1,200 mg but some patients may require a higher dosage. However, one should reduce the dose and frequency for patients with impaired renal function since the medication is eliminated unchanged through the kidneys.4
The most common adverse effects include dizziness, somnolence, fatigue and nystagmus. These side effects usually only last for the initial two to three weeks of therapy.
Gabapentin is a very effective drug with minimal propensity to interact with other drugs. We have found this agent to be of benefit in amputees complaining of phantom pain, especially after they have undergone transmetatarsal amputations.

A Closer Look At The Potential Of Foltx, Folgard And Tramadol
Foltx is a combination of three co-factors: folic acid, cobalamin (vitamin B12) and pyridoxine (vitamin B6). Folgard is a very similar agent but with different amounts of the co-factors. We are very excited about these medications and have increasingly prescribed them as our first drugs of choice.
Foltx was originally made to treat elevated homocysteine levels in patients who are at increased risk for heart disease. Factors causing increased homocysteine levels include smoking, chronic high alcohol consumption, post-myocardial infarction, post-stroke and increasing age. It is also indicated for homocystinuria, dialysis, ESRF, peripheral vascular disease (PVD) and coronary artery disease (CAD).
There are relatively few side effects or drug interactions with Foltx. However, one should avoid giving pyridoxine to patients receiving levodopa as pyridoxine antagonizes this drug. Also keep in mind that concurrent use of phenytoin and folic acid may result in decreased phenytoin efficacy.
We have had very good results in treating diabetic neuropathy with Foltx. Patients usually start feeling positive effects in about six weeks. If patients are unable to afford the medication, we put them on a vitamin B complex pill.
Tramadol (Ultram) is a central-acting, non-narcotic analgesic that inhibits noradrenaline and serotonin uptake. Tramadol was evaluated in a multicenter clinical trial of 131 patients with painful diabetic neuropathy.8 The patients who received a daily dose of 210 mg had significant pain relief compared to the placebo. Side effects included dizziness, nausea, headache and somnolence.
When using Tramadol, one should initiate treatment at 50 mg/day and increase it by 50 mg a day.1 There does not appear to be an upper ceiling on dosage and reports of higher dose levels increasing efficacy are still pending.

Only Consider These Drugs When Other Medications Fail
Mexiletine is an antiarrhythmic drug that has been evaluated in three clinical trials for patients with painful diabetic neuropathy.
In one study, patients who received the highest dosage of mexiletine (675 mg/day) garnered significant nighttime pain relief.5 The other two clinical trials did not show any significant improvement between the placebo and mexiletine.6,7 However, the patients with predominantly stabbing or burning pain had a better response to mexiletine.
The effective daily dosages range between 450 to 675 mg/day. Common side effects include gastrointestinal disturbances, dizziness, tremors, palpitations, chest pain and headache. Given these potential side effects, obtaining a baseline EKG is required before initiating therapy. One should reserve this drug for patients who do not respond to therapy with safer profile drugs.
In regard to opioid therapy, neuropathic pain is not particularly responsive to it and there have been no definitive studies advocating opioids for diabetic neuropathy. However, many physicians place their patients on opioids for chronic longstanding pain. Be advised that chronic usage may cause constipation, nausea and sedation in elderly patients.
In one study, oxycodone was evaluated for post-herpetic neuralgia.9 Compared to the placebo, oxycodone resulted in reductions of persistent pain, allodynia and paroxysmal pain. However, when it comes to treating chronic pain, one should first utilize other drugs with safer profiles.

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