Requirements before proceeding:
- The patient should have a proven history of an immediate-type drug allergy
- AND There are NO acceptable alternate drugs. Requirements before proceeding:
Immediate reactions: Occur within one hour of exposure. Reactions include flushing, pruritus, urticaria, shortness of breath, chest tightness, angioedema, N& V, hypotension, etc. Delayed-reactions occur > 1 hour after exposure.
Contraindications to desensitization: Never attempt desensitization in patients with extreme allergic responses such as Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiform or similar reactions that include desquamation on skin blistering component. Also avoid desensitization in patients with a history of the following types of reactions: hepatitis, nephritis, serum sickness reactions.
Ideally, only highly-trained specialists with experience with desensitization procedures should perform the technique.
The patients with a history of more severe reactions other than those mentioned above may require a lengthy desensitization procedure that is initiated with a much lower concentration that is used by this program.
It is possible that late-occurring reactions may occur after desensitization with prolonged therapy with the offending agent such as serum sickness, hemolytic anemia, and nephritis.
REMEMBER that a desensitization procedure brings about a TEMPORARY tolerance. Interruptions in therapy or after discontinuation of therapy, the patient’s hypersensitivity may return QUICKLY.
Most routes can be used for a desensitization procedure including IV, oral, and subcutaneous. The final route of administration can deviate from the initial route used for desensitization. Example: IV desensitization procedure –> oral therapy thereafter.
The desensitization procedure may have to be aborted for severe reactions including intractable hypotension or laryngeal edema that does not immediately respond to therapy with epinephrine. As mentioned earlier experience with the desensitization process is imperative.