Many patients with diabetes have been told to take Metanx by their podiatrist or other doctor?
Metanx is an expensive supplement. It is not a “drug”.
Technically, Metanx is called a “medical food” by the FDA.
But Metanx is only available by prescription.
Metanx is supposed to be used only under medical supervision.
Metanx contains a form of three different B vitamins: B12, B6 and the B vitamin called folic acid. Metanx is taken by mouth.
Metanx typically is prescribed to help patients who have nerve damage from diabetes. This is called diabetic neuropathy. Many podiatrists are advising their patients to take Metanx to help reduce pain from diabetic neuropathy. There are several prescription medications available to relieve the pain from diabetic neuropathy.
A very effective and low cost medication for painful diabetic neuropathy is a tricyclic antidepressant. Tricyclic antidepressants or TCAs are available as low cost generics.
In low doses, I find that about 90% of my patients get relief from a TCA.
I usually prescribe 10-20 milligrams of imipramine at bedtime. The imipramine is taken every day not as needed. Reports describing the efficacy of imipramine date back to the 1980's.
Many docs fail to think of TCAs for neuropathic pain.
They are not promoted like the newer pricier brand name drugs are.
And many patients can stop the TCA after several months. The pain just seems to go away over time. But that does mean the nerves are healed.
Other drugs proven effective for painful diabetic neuropathy are far more costly but might work when imipramine does not.
Cymbalta is one of these. Cymbalta has many other proven benefits.
A more expensive drug chemically related to gabapentin is Lyrica.
But there is no good evidence that Lyrica is worth the extra cost over gabapentin when used to reduce pain caused by diabetic neuropathy.
Okay let’s get back to Metanx. How effective is Metanx?
Well first, you should know that the FDA does not approve or regulate medical foods like Metanx. So Pamlab, the manufacturer, is free to make many claims for this product.
Do randomized controlled trials show benefit with Metanx?
Do these studies compare Metanx to a cheap dietary supplement of the vitamins that you can get without a prescription?
Well most of the studies done with Metanx had no control arm. That means they were not rigorous well done studies.
And many were done by a single podiatrist in St. Louis.
That fact alone should make you a bit skeptical.
But just recently, a randomized controlled trial of Metanx was done that showed reduced pain in those given Metanx as compared to placebo. There appeared to be no improvement in nerve function in this study that only lasted 6 months. It is not known if Metanx is any better than just a cheap vitamin B12 supplement.
And the long term safety of folate supplements is not clear. Remember folate and vitamin B6 are in Metanx.
One large trial found an increase in cardiovascular events when folate and vitamin B6 were given in combination after a previous myocardial infarction (heart attack). Two other trials published in 2006 and 2008 with different types of patients did not show this. The forms of B6 and folate used in these studies are different from that in Metanx.
Some patients might benefit from Metanx because their vitamin B12 level improved and was actually slightly low to start with. B vitamins are important for nerve function and vitamin B12 deficiency is common, and much more common in those taking metformin, a drug commonly used for Type 2 Diabetes.
In fact, those who tended to feel better in this recent trial may have had larger drops in their level of a substance called methylmalonic acid or MMA for short. MMA tends to be high in those who lack Vitamin B12. Vitamin B12 supplementation brings the MMA back down to normal.
What this suggests is that just taking B12 might work just as well as Metanx.
A recent report found that some people may be B12 deficient even though the blood test suggests they are fine. This can be a challenging problem.
Recently I have been testing both MMA and vitamin B12 in my patients who have evidence of neuropathy. B12 deficiency can be missed if you just check the B12 level. But a level above 400 pg/ml is probably normal.
Of course, most neuropathy in people with diabetes is from the diabetes not from B12 deficiency but patients can have both.
To sum all this up, Metanx might be helpful to reduce pain from diabetic neuropathy but its long term safety is not clear and my guess is that it is no more effective than a cheap B12 supplement. Pain from diabetic neuropathy goes away over time in most patients and the pain improves with better glucose control. Low cost prescription medication often is very effective.
So, is Metanx worth it? Probably not.
Daniel Weiss MD CDE FACP PNS CPI