The Problem

A mother whose daughter received an overdose of an oral iron product because of her difficulty understanding OTC iron supplement labels contacted the Institute for Safe Medication Practices. The mother was confused about the relationship between ferrous sulfate and elemental iron, each of which appeared on the label. She explained that she spent over an hour trying to figure out how much her daughter was receiving before she realized her child was receiving more than prescribed. Similar reports from patients and health professionals indicate that confusion is not uncommon.

Unfortunately, manufacturers have no standardized way to express the strength on the front panel of cartons.As OTC dietary supplements, iron products are regulated by the FDA's Center for Food Safety and Applied Nutrition (CFSAN). Regulations require a "common or usual name" of the product on the front panel. This allows manufacturers to label their products as "Iron" and express the strength in terms of elemental iron (eg, Iron 65 mg), as the salt form (eg, Ferrous Sulfate 325 mg), or in ways that make it difficult to interpret whether the salt form or elemental iron strength is indicated. Wording that the product is a "dietary supplement" or "iron supplement" also must be on the label. Finally, the "Supplement Facts" portion of the product label must indicate the amount of "iron," which, according to a CFSAN representative, means elemental iron, contained in each dosage unit.

Unlike the information presented in the "Supplement Facts," prescribers often communicate doses for iron supplements in terms of the salt form, not as elemental iron, which contributes to confusion. Thus, if a prescriber tells a patient to take 325 mg of ferrous sulfate or 325 mg of "iron," patients may read the amount of elemental iron and figure they need to take 5 tablets (5 x 65 mg = 325 mg) for each dose. We have even heard from practitioners who have similarly misinterpreted iron supplement labels. For example, after receiving a product labeled "Iron (as ferrous sulfate) 65 mg," a nurse in a skilled nursing facility calculated that 5 tablets were needed for a single dose of ferrous sulfate 325 mg. Fortunately, she realized that 5 tablets per dose seemed odd, and a call to the facility's pharmacist helped prevent a serious error. Who knows how many errors may go undetected, though— leading to patients receiving unintended amounts of elemental iron.

Safe Practice Recommendations

Since most iron supplements are available over the counter, patients may purchase products in any number of places, including the pharmacy, without a pharmacist's assistance. In order to minimize the likelihood of errors with iron supplements, consider the following:

•Ideally, all dosages should be expressed in terms of milligrams of elemental iron. Because prescribers often express doses in terms of the ferrous salt form, however, while some package labeling indicates strength in terms of elemental iron, both should appear in all forms of communication (eg, prescriptions, pharmacy labels, manufacturer labels, drug references)—for example, ferrous sulfate 325 mg (elemental iron 65 mg).

•Ensure that package labels clearly express iron dosages. If unclear, provide a pharmacy label with proper patient instructions.

•Verify that the selected dosage falls within the guidelines for iron replacement therapy for the patient's age and weight

•Store iron supplements behind the pharmacy counter, and require a pharmacist to provide counseling regarding dosing instructions. If this is not possible, place products near the pharmacy checkout in plain view of the pharmacist to capture an important counseling opportunity. At minimum, use "shelf talkers" near these products that instruct patients to ask for a pharmacist's help when selecting iron supplements.

•Educate staff and patients that iron-containing products are available in salt forms such as ferrous gluconate, sulfate, and fumarate. Emphasize the difference between elemental iron and its salt forms.

•Stress the importance of keeping these products out of the reach of children. If an accidental ingestion occurs, recommend contacting the nearest poison control center (800-222-1222) immediately.

Dr. Gaunt is a medication safety analyst and the editor of ISMP Medication Safety Alert! Community/Ambulatory Care Edition.

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