Beta Lactam Allergies

Question 1

How likely is beta-lactam allergy?

Answer 1

In a given group of 10,000 patients
1000 will report they have a pen allergy
<100 have true IgE-mediated pen allergy
1 to 3 will have cephalosporin cross reactivity
1 will have anaphylaxis when given penicillin

Question 2

What is a beta lactam allergy?

Answer 2

If you are allergy is to beta lactam ring, the patient will be allergic to all beta lactam

So also could be allergic to the side chain

Question 3

Cross sensitivity

Answer 3

Cephalosporin and penicillin cross-sensitivity rate often quoted as up to 10% ,however it is not that high; more like 1-3% or even less
Carbapenems have ~ 1% cross-reactivity with penicillins

Question 4

Reaction to beta lactam into 3 separate groups

Answer 4

Penicillin Adverse Effects
Severe Penicillin Adverse Effects
True IgE mediated allergy

Question 5

Penicillin Adverse Events

Answer 5

Diffuse non-itchy rash, GI upset, headache
Safe to give penicillins and cephalosporins

Question 6

How long does penicillin adverse events take to being and end?

Answer 6

Begin after 2-5 days
May last several days to a week

Question 7

Severe Penicillin Adverse Effects

Answer 7

Can be life threatening

Stevens-Johnson syndrome
toxic epidermal necrolysis(TENS)
Intestitial nephritis
Hemolytic anemia
Serum sickness
All beta lactam are contraindicated

Question 8

True IgE Mediated Allergy

Answer 8

Itchy Rash and Hives
Angioedema, hypotension, bronchospasm
Can be life-threatening
Usually occur < 1 hour
Anaphylaxis

Question 9

Management for Anaphylaxis

Answer 9

Stop the offending agent
ABC (Airways breathing circulation
CPR if required
Treat with epinephrine

Give O2, IV fluids, nebulized salbutmol, glucagon if patient on a beta blocker, IV corticosteroids, diphenhydramine, ranitidine

Question 10

Skin Test for beta Lactam allergy

Answer 10

If negative can safely give cephalosporins and penicillins
Positive - avoid penicillin
Choose cephalosporin with dissimilar side chains or use alternative agent
Or graded cephalosporin challenge
De labelling is important

Question 11

Sulfonamide drugs contain

Answer 11

SO2NH2

Question 12

Rates of Sulfa allergies

Answer 12

Antibiotic Sulfonamide 4.8%
Non antibiotic Sulfonamide 2%