If it truly was serum sickness after amoxicillin clavulanate, I would recommend avoiding amoxicillin clavulanate for at least the next several years. After 2-3 years, an oral amoxicillin 250 mg challenge and 5 days of observation would be a safe way to determine current tolerance. There is no good data regarding the need to avoid other non-amino penicillins in the setting serum sickness. If another penicillin was needed it would probably be safe to do an oral penicillin 250 mg challenge with 5 days of observation. There is no need to avoid cephalosporins.
I hope this information is of help to you and your patient.
Eric Macy, MD, MS, FAAAAI