Drug allergies and beta-lactam allergies

Question 1

Are true antibiotic allergies or reported antibiotic allergies more common?

Answer 1

reported antibiotic allergies are more common

Question 2

What can be said about patients with antibiotic allergies who are prescribed a new AB prescription?

Answer 2

AB allergies are usually from the past, so they will generally not have signs or symptoms of allergy

Question 3

How likely are beta-lactam allergies?

Answer 3

In 10,000 pt
1000 will report a pen allergy
Less than 100 will have a true IgE-mediated pen allergy
1-3 will have cephalosporin cross reactivity
1 will have anaphylaxis when given penicillin

Question 4

What can be said if a patient is allergic to the beta-lactam ring structure? How about a a side chain of a penicillin or other antibiotic?

Answer 4

If the bet-lactam ring , then the patient will be allergic to all beta-lactams
If only a side chain, then only allergic to drugs with the same side chain (can switch to another AB)

Question 5

What is the cross-reactivity rate of carbapenems with penicillins?

Answer 5

1%

Question 6

What are the three beta-lactam reactions?

Answer 6

Penicillin adverse events
Severe penicillin adverse effects
True IgE mediated allergy

Question 7

Explain penicillin adverse events. What occurs?

Answer 7

Diffuse non-itchy rash, GI upset, headache
The rash occurs in less than 10% of pt

usually occur after 2-5 days of therapy
May last several days up to a week

Not IgE mediated (so not allergic- there is a separate category for IgE)

It is safe to give penicillin and cephalosporins to these pt

Question 8

Explain penicillin adverse events. What occurs?

Answer 8

Diffuse non-itchy rash, GI upset, headache
The rash occurs in less than 10% of pt

usually occur after 2-5 days of therapy
May last several days up to a week

Not IgE mediated (so not allergic- there is a separate category for IgE)

It is safe to give penicillin and cephalosporins to these pt

Question 9

Explain severe penicillin adverse effects.

Answer 9

SJS, TENS, interstitial nephritis, hemolytic anemia, serum sickness

Not IgE mediated

All beta-lactams are contraindicated (can’t use any in this family)

Skin-testing and desensitization are not recommended as the pt will react poorly

Question 10

What is a true IgE mediated allergy?

Answer 10

This occurs in 1:10,000 patients

Itchy rash or hives (very itchy)
Angioedema, hypotension, bronchospasm
Can be life-threatening
Occurs in less than 1 hour after the dose
Pt goes into anaphylaxis

Question 11

What to do in allergic reactions to penicillin?

Answer 11

Stop the offending agent, stop the drug
ABC- assess airway, breathing, and circulation - support the airway
CPR if needed
Use an epipen (epinephrine 1:1,000) - IM
Oxygen, IV, nebulized salbutamol (bronchodilation), glucagon if pt on BB, IV corticosteroids, diphenhydramine, ranitidine

Question 12

What is the epipen dosing?

Answer 12

Adults 0.3-0.5mg/kg
Children 0.01 mg/kg

every 5-15 minutes up to 3 injections

Question 13

Explain skin testing

Answer 13

Tells us if the patient is allergic or not

if negative, can safely give cephs and pens
if positive, then avoid pens, but choose a cephalosporin with a different side chain

Question 14

What do you do if there are no alternatives for a positive skin test?

Answer 14

induction of drug tolerance aka desensitization

Question 15

What is desensitization? What is the dosage form needed to perform?

Answer 15

Use small amounts of the drug, and keep up with it to induce tolerance in the pt
If there is stoppage at any point, then the patient will be allergic again
Oral > IV

Question 16

Why is de-labelling important?

Answer 16

So that the patient can receive the care they need
Pt don’t like to remove their pen allergies on their file if it is already there

Question 17

What is the part of sulfonamide drugs that are responsible for sulfa allergies?

Answer 17

SO2NH2 (arylamine at the N4 position or the N-containing ring attached to N1 Nitrogen of the sulfonamide group)

Question 18

What are some examples of drugs that contain SO2NH2?

Answer 18

AB, thiazide and loop diuretics, oral hypoglycemic, COX-2 inhibitors, carbonic anhydrase inhibitors
Antivirals, probenecid, tamsulosin, triptans, zonisamide

Question 19

What are the rates of allergic reactions of AB sulfonamides and non-AB sulfonamides?

Answer 19

4.8% and 2%

Question 20

True or false: It is likely that there will be cross reactivity between sulfonamide antibiotics and non-antibiotics

Answer 20

False

Question 21

What is seen in Sulfa allergies?

Answer 21

Delayed cutaneous reactions are common
-Fever followed by rash - morbilliform or maculopapular
- May result in SJS or TENS

IgE mediated rxns are rare such as anaphylaxis

Question 22

What is important to gather as HCP for AB and sulfa allergies?

Answer 22

Get the pt detailed allergy history by asking them questions about their rxns