What is the Extent of Safety and Efficiency of Drug Desensitization on

Patients with Allergic Reactions?

Cindy Law

Dr. Mary Lee-Wong

What are Allergies?

An abnormal sensitivity to an allergen that is inhaled, eaten, or touched

An overreaction of a hypersensitive immune system

Misidentification of a harmless substance as harmful

Common Types of Allergies

Allergic rhinitis Food Medication Insect stings Latex chemical

Allergies and the Immune System

B-lymphocytes &T-lymphocytes

Lymphocytes identifies a foreign invader

Foreign antigens cause production of antibodies

5 types of immunoglobulins

Mast Cells and Basophils

Allergy Cascade

Anaphylaxis

Severe allergic reaction prominent in dermal and systemic signs

Common causes are food, medication, insect stings, and latex

symptoms may begin in as little as five to 15 minutes to up to two hours after exposure to the allergen

EpiPen

epinephrine is a synthetic version of a naturally occurring hormone also known as adrenaline

causes rapid constriction of blood vessels, reversing throat swelling, relaxing lung muscles to improve breathing, and stimulating the heartbeat.

Allergy Tests

Scratch test Diluted extract of the

possible allergen to the back or arm

Scratching the skin with the needle

Blood tests

Places and Symptoms of Reactions

The sensitized immune system produces antibodies against allergens which cause the release of histamines into bloodstream

Treatments

Avoidance Medication Immunotheraphy The injections help the immune system to

produce fewer IgE antibodies, while also stimulating the production of a blocking antibody IgG

Drug Desensitization

Drug Desensitization allows safe delivery of an antibiotic to a patient which has an IgE medicated sensitivity to the drug by administering it in small doses until a full therapeutic dose is clinically tolerated

The procedure entails risk of acute allergic reactions, including death

Drug Desensitization Protocols

1.    Skin test patient to determine degree of sensitivity:    a.    Dilute available drug solutions/suspension to 1/3 mg/ml.    b.    Prepare three tenfold dilutions.    c.    Perform prick-puncture testing with 1:1000 dilution    d.    If negative, serial intradermal tests (0.02 ml [2-4mm bleb] in duplicate) up to and including 3 mg/ml stock; discontinue testing when >8 m wheal is observed.  Test is positive if both duplicate wheals increase significantly (>2-3 mm) 20 min after placement compared with diluent control.2.    Prepare sufficient quantities of drug solution/suspension for desensitization regimen in half-log 10 dilutions (threefold and tenfold dilutions from       concentrate [1-3 mg/ml]).

Protocol Cont’d

1.    Establish baseline monitoring of patient in medical setting appropriate for patient's clinical conditions and the nature and severity of the prior reaction.       Start a secure intravenous infusion.2.    Starting dose: If skin test negative and test is unvalidated, begin with 0.1 ml of 1/3 microgram/ml solution/suspension; if skin test positive, begin 100-fold below the dose producing a midpint (5-8 mm wheal) reaction.3.    Route; oral by ingestion or ng tube in 30 ml water; parenteral by intradermal (<0.2 ml), SC (0.2-0.6 ml), or intramuscular (>0.6 ml) injection.

Protocol Cont’d

4.    Dosing interval: 15-20 min for parenteral doses; 20-30 min for oral dosing.  Repeat dose for mild systemic reaction: drop back two doses (tenfold) for moderate reactions, further for any reactions producing hemodynamic changes.5.    Dose escalation; half-log 10 (-threefold) increments; e.g., 1 g, 3 g, 10 g, 30 g, 100 g, etc.6.    If IV therapy is indicated, begin infusion to deliver a dose equivalent to the last oral/parenteral dose slowly over 1 hour. Double the infusion rate every       hour until target therapeutic dosing is achieved.

Penicillin Drug Desensitization

Background: – A 32 year old female is pregnant and is

diagnosed with syphilis – Penicillin is the ideal antibiotic to treating – The mother is allergic to penicillin – Her obstetric history included one vaginal delivery

at term and four subsequent spontaneous abortions at 12 to 16 weeks.

Bibliography

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Special Thanks to:

Harlem Children Society Dr. Sat Dr.Mary Lee-Wong Beth Israel Medical Center