US Pharm. 2008;33(3):100.

Recently, a mother wrote to the Institute for Safe Medication Practices (ISMP) to express confusion about iron products and the relationship between ferrous sulfate and elemental iron. It was later discovered that her daughter was receiving more than the prescribed amount. Unfortunately, similar reports reveal that these issues contribute to many errors, which can be serious since overdoses may lead to severe gastrointestinal problems, liver damage, and death.

Unlike information presented in 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 think they need to take five tablets (5 x 65 mg = 325 mg). In addition, manufacturers do not express the strength on the front panel of the package in a standardized way. Some manufacturers label their products as "iron" and express the strength as elemental iron (e.g., iron 65 mg); some label products as the salt form (e.g., ferrous sulfate 325 mg), while others use ambiguous labeling. We have seen only a few examples where both strengths are prominently expressed on the front panel.

Errors involving ferrous sulfate liquids are often the result of confusion between two formulations. Fer-In-Sol drops contain 15 mg iron/0.6 mL, equivalent to ferrous sulfate 75 mg/0.6 mL, making it about three times more concentrated than the elixir, which contains 44 mg iron/5 mL, equivalent to ferrous sulfate 220 mg/5 mL. Recently, we heard from the mother of an anemic 1-year-old child. The physician wrote a prescription for "ferrous sulfate 220 mg/5 mL" with instructions to give "3/4 teaspoon twice daily." At the pharmacy, the mother was instructed to use Fer-In-Sol drops. When the bottle had been finished in less than seven days she became suspicious and consulted with a different pharmacist, who realized that the drops had mistakenly been recommended instead of the elixir. Subsequently, the child, who weighed 10 kg, received 190 mg of elemental iron per day for seven days instead of 66 mg per day--a three-fold overdose. Poison Control was contacted, and the child was taken to the hospital for evaluation. Fortunately, no serious harm resulted.

Safe Practice Recommendations
Since most iron supplements are available OTC, patients are often directed to the vitamin aisle to choose a product without a pharmacist's assistance. In order to minimize the likelihood of errors, consider the following:

• Practitioners should clearly express the dosage as milligrams of elemental iron in patient charts, as well as on prescriptions, pharmacy labels, and medication administration records.

• Pharmacists should clarify prescriptions for liquids that contain only the volume to be administered. Dosing instructions should include milligrams of elemental iron as well.

• Ideally, these products should be stored behind or near the pharmacy counter to capture an important counseling opportunity. Pharmacies could place signs near iron supplements to recommend that patients ask for assistance.

• Pharmacists should verify that the dosage falls within the guidelines for iron-replacement therapy for the patient's age and weight.

Educate staff and patients about the relationship between elemental iron and its salt forms. Products containing iron are available as ferrous salts (gluconate, sulfate, fumarate), which confer different bioavailability of elemental iron (12%, 20%, 33%, respectively).

• Ensure that patients understand how to measure the proper dose for liquids, and advise them to use only the measuring device included in the original packaging.

• Manufacturers should clearly express iron dosages as both the elemental iron and the iron salt on packaging. If unclear, pharmacists could place a pharmacy label with clarified instructions on the package. Pharmacists should try to avoid ordering poorly labeled products.

To comment on this article, contact editor@uspharmacist.com.