Preservative-free drugs may still contain sulfites, making it essential for pharmacists to examine both active and inactive ingredients when dispensing drugs to all patients, but especially for those who are sensitive to sulfites.
Sulfites are often used in drugs, foods, and beverages as preservatives or antioxidants. The challenge with sulfites is that they can present safety concerns for patients who may be allergic to them.
In drugs...[sulfites] are used as antimicrobial preservatives, they are used as antioxidants to prevent the drugs from breaking down, from discoloring, and to make the drugs more stable,” said Helena Dummler, PharmD, Clinical Pharmacist in the Data Structure Group at First Databank, a drug knowledge-base publisher.
Some research has suggested there could be concerns with neurotoxicity when sulfites are used in the central nervous system, although Dummler said findings into this area have been inconsistent.
Despite these safety concerns, products that contain sulfites do not always have clear labeling. According to the FDA, products that contain a sulfite should include a warning statement as part of its labeling stating that the product contains a sulfite that “may cause allergic-type reactions including anaphylactic symptoms and life-threatening or less severe asthmatic episodes in certain susceptible people.”
“Labeling of sulfites can be tricky and that’s why it has become an issue for us of late,” Dummler said. “Drugs that are labeled as preservative-free can still contain sulfites. They might say that they are not used as preservatives; they are used as antioxidants. Or there could be trace amounts of sulfites that are residuals from the manufacturing of the drug,” she added.
Whether or not a drug gets labeled as preservative-free can also vary from one manufacturer to another, she said.
“If you look at two drug formulations that are exactly the same in terms of their active ingredients and their inactive ingredients one may say preservative-free on their labeling and the other may not,” she said.
Pharmacists need to be familiar with the kinds of drugs that may contain sulfites so they can clearly examine the ingredient list before treating patients, Dummler said.
Sulfites can be commonly found in epinephrine, phenylephrine, antibiotics, anesthetics, opioids, and eye drops.
Adverse Reactions Vary
Allergies to sulfites can range from mild to life threatening and cause anything from itching and dermatitis to anaphylaxis. Adverse allergic reactions are typically more of a concern in patients with asthma.
“In particular people who are on steroid therapy, or who are dependent on steroids, and people who have highly reactive airways might be more prone to the more serious reactions,” Dummler said.
Even drugs labeled as preservative-free may still contain ingredients that can function as preservatives in other formulations, she said.
“It’s always important to review the product labeling and the warning, especially if you are dealing with someone who has had an anaphylactic reaction to sulfite,” she said.
Dummler also recommended paying particular attention to drugs that are used in the central nervous system.
“It’s worth taking the extra step to look closely at the product labeling to make sure that it doesn’t contain any sulfites,” she said.
First Databank collects information about inactive ingredients of drugs and has a module on inactive ingredients that its customers can use and integrate into their electronic health record. The module triggers an alert when a drug is prescribed for someone allergic to sulfites.
Update 8/17: Fixed quote from Helena Dummler, to say "drugs labeled preservative-free may still contain ingredients that can function as preservatives in other formulations" from "drugs labeled as preservative-free may still contain ingredients that are being used as preservatives."