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by Sarah Johnston Miller, Pharm.D., BCNSP

(Note from Dr. Wes Wilson: Looking at this question, I felt it would be wise to refer it to a pharmacist who is actively involved in both patient care and in teaching students about such problems. Dr. Sarah Miller is Professor of Clinical Pharmacy at the University of Montana, and is also a consultant at St. Patrick Hospital in Missoula, Montana. Her answer should be helpful.)

Q: Which nonprescription drug products for treatment of common cold symptoms should a person with diabetes avoid?

A: There is some concern about the effect some nonprescription (over-the-counter) medications may have on blood sugar control. The diabetic patient should always remember that, in general, "sick days" may be associated with fluctuations in blood sugar. This may be related to the stress of being sick, or to changes in dietary intake during illness. Your nonprescription medications may not be at fault at all--but it pays to know. A severe bout of the common cold (a viral illness) could certainly produce "sick days," elevated blood sugars--without any effects from your nonprescription or other medications. When you're sick, test your blood more often.

Textbooks may list quite a few classes of potentially-problematic medications, though many of these are in reality not very significant. Regardless, the diabetic patient should always contact their health care provider (physician, diabetes educator, or pharmacist) prior to taking any new nonprescription medication. This includes "lternative"remedies purchased at the health food store or elsewhere; "natural" does not mean "safe from interactions!"

You should be cautious that many nonprescription medications, including those targeting symptoms of the common cold, contain multiple ingredients. Another caution relates to the "branding" of products. Don't assume that all products carrying the same name (like "Robitussin") contain the same ingredients. For example, the content of Robitussin differs from that of Robitussin CF, which differs from that of Robitussin PM. In addition, the diabetic patient should be aware many nonprescription medications for the common cold (especially liquid medications and cough drops) contain sugar. Many sugar-free alternatives are available, and these may be better options for the diabetic patient.

Classes of nonprescription medications most commonly utilized to relieve symptoms of the common cold include decongestants, antihistamines, analgesics/antipyretics, antitussives, and expectorants. I will briefly discuss potential effects on blood sugar of some representatives of these classes.

Decongestants relieve the nasal stuffiness and congestion characteristic of the common cold. In oral form, the most common decongestants are pseudoephedrine (Sudafed) and phenylephrine. Oral decongestants as a category have the most potential for affecting your blood sugar control. They can increase blood sugar by preventing insulin secretion, by decreasing glucose uptake into peripheral tissues, and by stimulating glycogen (the body's own stored glucose reserve) breakdown. Diabetic patients should definitely check with their health care providers before using an oral decongestant.

Decongestants are also available for direct administration (spray or drops) into the nose. These include oxymetazoline (Afrin), phenylephrine (Neo-Synephrine), and xylometazoline (Otrivin). Since these nasal sprays are less fully absorbed into the bloodstream than are the oral agents, they should have less effect on blood sugar levels. However, such sprays should not be used for more than three to five days at a time, as prolonged use can worsen nasal congestion.

Antihistamines, more commonly used to treat allergic rhinitis, may have some limited benefit against the common cold, as they decrease runny nose and sneezing. Common nonprescription antihistamines include diphenhydramine (Benedryl Allergy Tablets), chlorpheniramine (Chlor-Trimeton Allergy Tablets) and loratadine (Claritin). This class of drugs has no effect on blood sugar.

Analgesics are used for aches and pains associated with the common cold, and antipyretics address fever. Aspirin, acetaminophen (Tylenol), ibuprofen (Advil), naproxen (Aleve) and ketoprofen (Orudis) are nonprescription members of this category.

Low dose aspirin (up to 325mg per day) is recommended for diabetic patients, to help prevent cardiovascular disease. Very high dosages of aspirin and other salicylate drugs can cause hypoglycemia, and should thus be avoided by diabetic patients. Aspirin should not be given in any dosage to children who have a viral infection, as it may precipitate a severe illness known as Reye's syndrome. Acetaminophen is probably the safest analgesic/antipyretic for diabetic patients. Ibuprofen, naproxen, and ketoprofen do not have significant effects on blood sugar, but should be used with caution by patients who have renal insufficiency.

Antitussive agents help suppress cough. The most common active ingredient in this class is dextromethorphan. Diphenhydramine, an antihistamine, described above, is also an approved antitussive, though considered "second line" for cough. Codeine is available by prescription in some states, without prescription in others. None of these cough suppressant medications significantly affect blood sugar control.

The final major category of agents used to treat symptoms of the common cold is the expectorants. These medications loosen respiratory tract secretions and make coughs more productive. The most common active ingredient in this category is guaifenesin--which has no effect on blood sugar control.

When considering nonprescription medications, another issue of concern is whether or not they interact with other medications (especially prescription meds) the individual is already taking. Though many interactions listed in the references are clinically insignificant, a few can be significant, or even life threatening. If you are taking medications for diabetes, or to deal with a diabetes complication such as heart disease, or even treatment for depression, check with your doctor, diabetes educator and pharmacist regarding possible interactions between these medications, any "alternative/herbal" substances you might be taking, and nonprescription medications used to relieve symptoms of the common cold.