Alcohol May Trigger Neuropathy, Even in Those With Diabetes

Alcohol use may cause or accelerate neuropathy even in people with diabetes, two endocrinologists point out in a commentary.

So it's important to ascertain if a person with distal symmetrical polyneuropathy (DSP) uses alcohol excessively because neuropathic symptoms are unlikely to improve if that use continues.

And attempted treatment may be dangerous, as some of the most common drugs used to treat neuropathic symptoms can suppress respiration when combined with alcohol, Alabama endocrinologists David S.H. Bell, MB, and Edison Goncalves, MD, explain in their piece, recently published in Diabetes Therapy.

They note that diabetes is the most common cause of neuropathy, and alcohol the second-most common. In people with diabetes who drink, both may contribute to worsening neuropathy symptoms. Those symptoms — including numbness, tingling, pain, and early motor involvement of the toes — are nearly indistinguishable between neuropathy caused by diabetes and by alcohol.

But there is little overlap between the two mechanisms for the nerve damage, so the effects are likely to be additive, say Bell, of Southside Endocrinology, Irondale, Alabama, and Goncalves, of Grandview Endocrinology, Homewood, Alabama.

Yet, they note, "Patients with diabetes and DSP are routinely evaluated for etiologies other than diabetes, including vitamin B12 deficiency, paraproteinemia, hypothyroidism, and drug or autoimmune-induced neuropathy. However, the most common cause of DSP, next to that of diabetes, is alcohol intake, which is almost never evaluated."

Regardless of glycemic control, nerve damage will continue to progress if the patient doesn't stop drinking and if any thiamine deficiency isn't corrected, they add.

Bell, a retired professor of medicine at the University of Alabama, Birmingham, told Medscape Medical News, "I've come to the stage where I tell them, 'I'm not going to treat your pain unless you give up alcohol because it's dangerous and you're not going to get any better.'"

Asked to comment, Michael James Polydefkis, MD, director of the Cutaneous Nerve Lab and professor of neurology at Johns Hopkins Medicine, Baltimore, Maryland, told Medscape Medical News, "I agree with the commentary in principle."

He noted that smoking, high blood pressure, and high cholesterol can all worsen diabetic neuropathy, "so it makes sense that someone with diabetes who uses alcohol would have worse neuropathy. But we need more concrete data."

How Far Should You Go to Uncover a Patient's Drinking Habits?

Of course, patients don't always volunteer their drinking habits. And when asked about it, they typically underestimate. Bell and Goncalves report three cases with severe neuropathy in which the patients — two of the men with reasonably controlled type 2 diabetes taking metformin — had initially denied excess alcohol use but it was later discovered, in one case after death.

The third case was a woman with type 1 diabetes with no retinopathy or kidney problems but with severe neuropathy that had advanced to gastroparesis. Her heavy drinking was only revealed after it led to acute pancreatitis.

Because of that, the two endocrinologists recommend measuring urinary ethyl glucuronide (EtG) levels to assess the degree of alcohol intake in patients presenting with DSP. A metabolite of alcohol formed by glucuronidation, EtG is detectable in the urine for up to 90 hours after alcohol intake, and for longer periods in a hair sample.

Other tests, such as elevated liver enzymes (serum glutamic oxaloacetic transaminase [SGOT] higher than serum glutamic pyruvic transaminase [SGPT]), triglycerides, and uric acid, or decreased magnesium and folic acid levels will usually only be abnormal with very high alcohol intake.

Overall, they recommend "rigorous" screening including biomedical testing for alcohol use in all patients presenting with DSP, and in particular, painful DSP.

Polydefkis commented, "It's true that people often underestimate their alcohol use. We're kind of going on the honor system. I always discuss this with patients, as well as smoking. If they say they don't [drink or smoke], I say, 'Good, don't start.' If they drink alcohol, I tell them we don't know the threshold but that drinking a lot doesn't serve you well."

He doesn't support universal biochemical testing for alcohol use, though. "I guess I feel a bit differently in that I view my role as that I'm here to help the patient. If they don't tell me the truth, I'm not sure I need to embark on a bunch of tests to prove that."

However, he added, "certainly I could see instances where [further testing] might be helpful in understanding a patient's presentation...In a person who presents with very mild diabetes and a prominent neuropathy we should be suspicious that it's not just the diabetes...That might be a situation where I'd probe deeper for alcohol."

Danger: Neuropathy Medications and Alcohol Don't Mix

Prescribing medications to treat neuropathic symptoms, such as tricyclic antidepressants, antiepileptics, serotonin reuptake inhibitors, norepinephrine reuptake inhibitors, and analgesics can suppress respiration when combined with alcohol. The label for pregabalin, for example, tells patients to avoid consuming alcohol while taking it, as this might potentiate the impairment of motor skills and sedating effects of alcohol.

"You have to be aware that they're drinking if you prescribe them medication," Bell pointed out.

Polydefkis acknowledged, "That's a fair point. We need to do a better job about that."

Overall, Polydefkis said of the commentary, "I think it's provocative. I think we need more concrete data, but the authors' points have some merit."

Bell has been speaking for over 25 years about the dangers of heavy drinking and alcohol-induced hypoglycemia, even with lower amounts of alcohol, in those with diabetes.

He told Medscape Medical News, "Most doctors probably don't think about it...People with diabetes do drink."

Bell has reported disclosures with Amarin and Esperion. Goncalves has reported a disclosure with Novo Nordisk. Polydefkis has reported no relevant financial relationships.

Diabetes Ther. 2021;12:2631-2634. Full text

Miriam E. Tucker is a freelance journalist based in the Washington DC area. She is a regular contributor to Medscape, with other work appearing in the Washington Post, NPR's Shots blog, and Diabetes Forecast magazine. She is on Twitter @MiriamETucker.

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