Guidelines
Reactions During Desensitization

Reactions During Desensitization

Reactions During Desensitization

While there have been no fatal reactions reported during desensitization, mild hypersensitivity reactions can occur in up to one-third of patients

Mild reactions:

  • The vast majority of patients who suffer mild reactions during desensitization can go on to complete the procedure
  • In cases of mild reactions, the desensitization procedure should be temporarily interrupted, and the reactions should be treated
  • Simply interrupting the desensitization, with no treatment, can resolve up to 90% of mild reactions
  • If reactions subside, or do not progress, the desensitization procedure can be restarted, going back one or two steps preceding the dose that caused the reaction, with or without adding intermediate dosing increments

In the very unlikely event of a severe systemic reaction, the desensitization procedure should be immediately discontinued, and the reactions should be treated immediately

Reaction Types & Action to Take

If mild SKIN reaction (i.e. erythema, rash, pruritis, urticaria) WITHOUT systemic reaction, administer:

  • Cetirizine 20 mg PO x 1 dose
  • Ranitidine 150 mg PO x 1 dose (or famotidine 20 mg PO x1 dose if ranitidine unavailable)

HOLD desensitization and contact the prescriber

If SYSTEMIC reaction (i.e. hypotension, wheezing, bronchospasm, angioedema), administer:

  • EPINEPHrine 0.3 mg IM x 1 dose STAT
  • DiphenhydrAMINE 50 mg IV direct x 1 dose
  • MethylPREDNISolone 125 mg IV x 1 dose
  • Salbutamol 4-8 puffs with aerochamber (if respiratory involvement)

Immediately STOP desensitization and contact the prescriber STAT

  • It is important to note that in patients with syphilis, treatment with penicillin can induce a Jarisch-Herxheimer reaction (fever, chills, myalgia, flushing and skin rash)
  • This reaction, which is often falsely diagnosed as a drug allergy, is thought to result from the rapid release of endotoxins and lipoproteins during the death of spirochetes
  • Jarisch-Herxheimer reactions begin approximately 4 hours after initiating penicillin, will peak at approximately 8 hours, and tend to subside within 16 hours