Antibiotic Stewardship/Basics

You shouldn't, oftentimes MIC is not tested to the exact number, just a less than or greater than, so we don't even know if one is really a lower MIC than another. Even when we have an exact number, they are not reliable, and may differ if more tests are done, so antibiotic descision making should be based on other factors.

Quinolones, tetracyclines, trimethoprim/sulfamethoxazole

Macrolides, tetracyclines, ampicillin, clindamycin, amox/clavulanate

Lower risk, about 2-5% chance of cross reactivity

lower risk, can be predicted with skin testing or oral dose challenging

Itching, rash, hives, angioedema, respiratory distress, cardiovascular findings

anaphylaxis

IgE

Hemolytic anemia
neutropenia
thrombocytopenia

cell destruction

IgG

Drug fever
Serum sickness
vasculitis

immune-complex deposition, with or without complement activation

IgG

contact dermatitis
maculopapular rash
contact dermatitis

Macrophage, eosinophil, or T-cell activation

stevens johnson syndrome
toxic epidermal necrolysis

neutrophil activation

The specific drug that triggered the reaction, may consider using other drugs in the same class

The triggering drug and the entire class of medications it is in

After 10 years, about 80% of patients will lose reactivity and may be considered for another trial

Correlates with side-chain similarity

very low, 1-2% overall
dependent on side-chains, no common side chains means no increased risk
Common R1 sidechain means ~40% crossreactivity in type I patients and ~20% in type IV

very low, 1-2%

No increased risk

Cefadroxil and cefprozil

Cefaclor and cephalexin

Ceftriaxone
cefotaxime
cefpodoxime
ceftizoxime

aztreonam

None, can be given to patients with beta lactam allergies with no increased risk

90-95%

Fluoroquinolones, tetracyclines