PIC QUESTION OF THE WEEK: 05/30/05 Q: Can a patient who developed a rash with omeprazole be treated with pantoprazole? A: Cross-reactivity among the proton-pump inhibitors (PPIs) has been documented in a limited number of patients. The product literature for many of the PPIs includes a contraindication or precaution against their use in patients with prior “hypersensitivity” to substituted benzimidazoles . All PPIs are benzimidazole analogs. Older agents such as omeprazole and lansoprazole do not have this warning in their labeling. The majority of cases associated with cross-reactivity involve patients experiencing anaphylactic reactions to these compounds. In two reports, patients developed classic signs and symptoms of anaphylaxis within 45 minutes after receiving single doses of lansoprazole. In both cases, the patients had similar, but milder reactions to omeprazole several months earlier. Some patients exhibiting urticaria, angioedema, and hypotension with omeprazole have subsequently been skin tested with omeprazole, lansoprazole, and pantoprazole. Skin tests (prick and intradermal) were positive to each of these PPIs. There is some evidence these immediate-type reactions may be mediated by IgE. Lastly, a patient has been described who developed a lichenoid eruption to omeprazole. Three weeks later, he was challenged with lansoprazole and a similar reaction developed. Several months afterward, the patient inadvertently received pantoprazole and had a recurrence of the lichenoid reaction. Based on the available literature, it would not seem prudent to re-challenge a patient with any PPI, especially if they have had a significant reaction to one in the past. References: • •
Natsch S, Vinks MH, Voogt AK, et al. Anaphylactic reactions to proton-pump inhibitors. Ann Pharmacother 2000;34:474-6. Bong JL, Lucke TW, Douglas WS. Lichenoid drug eruption with proton pump inhibitors. BMJ 2000;320:283.
John G. Lech, Pharm.D.