Chapter 77: Drug Allergies & Adverse Drug Reactions Flashcards
What is an ADR
unintended pharmacologic effect
ADRs are categorized into which two types
Type A: predictable (most ADRs)
Type B: unpredictable
ADRs are different from medication erros because…
the drug is being administered correctly (dose, indication, etc) and someone then has an ADR
Type A reactions are dependent on
dose
account for 80% of ADRs
Type B reactions depend on ____ and include
patient specific factors (unrelated to pharmacologic mechanism)
- idiosyncratic reactions (e.g., SJS)
- pseudoallergic reactions (e.g., redman syndrome with rapid vanco infusion, itching after opioid administration)
- Drug intolerances (e.g., nausea with codeine)
- Drug allergies (immune mediated responses)
Type I allergic reactions occur how long after drug exposure
within 60 min
Ex) urticaria, bronchospasm, angioedema, anaphylaxis
Type II allergic reactions occur how long after drug exposure
Several days (5-8 days)
Ex) hemolytic anemia and thrombocytopenia
Type III allergic reactions occur how long after drug exposure
immune complexes ≥ 1 week
Ex) DILE
Type IV allergic reactions occur how long after drug exposure
48 hours to several weeks
Ex) SJS
REMS are developed by ____ and approved by ____ to ensure the benefits of the drug outweighs the risk
examples
Manufacturer
FDA
clozapine REMS, isotretinoin IPLEDGE
T/F: if a medication has a MedGuide, it only needs to be dispensed with the original Rx and it’s optional to dispense it with each refill
False - it must be dispensed with the original rx and each refill
When an ADR occurs, which scale can help determine the likelihood that a drug caused an adverse reaction
Naranjo Scale
0 = doubtful ADR; ≥9 = definite ADR
SE, adverse events and allergies should be reported to the ____
FDAs MedWatch program, which is called the FDA Adverse Event Reporting System (FAERS)
Post-marketing safety surveillance programs is also known as
Phase IV trials
upset stomach/nausea is ____
an intolerance, not an allergy
When dispensing medications that can cause photosensitivity, it is important to advise patients to use sunscreens that block both UVA and UVB, which are labeled as
Broad-spectrum
Drugs most commonly associated with photosensitivity
Amiodarone Diuretics (thiazide and loop) MTX Oral and topical retinoids Quinolones St. John's Wort Sulfa antibiotics Tacrolimus Tetracyclines Voriconazole
What is TTP
a blood disorder in which clots form throughout the body
Key drugs associated with TTP
Oral P2Y12 inhibitors (e.g., Plavix)
Sulfamethoxazole
What is the key to treating SJS and TEN
stop the offending drug
then fluid and electrolyte replacement, woudn care, pain medications
Which medications are CI in TEN, but may be used in SJS
Systemic steroids
DRESS management
stop offending agent
Anaphylaxis occurs within what time frame of drug exposure
seconds to minutes
Treatment for anaphylaxis
Epinephrine injection +/- Benadryl +/- steroids +/- IV fluids
Key drugs that are commonly associated with severe skin reactions
Abacavir Allopurinol Carbamazepine Ethosuximide Lamotrigine Modafinil Nevirapine PCNs Phenytoin SMX
Dose for EpiPen
1 mg/mL
Where should EpiPen be injected
into the middle of the outer thigh
At what angle should an EpiPen be injected
90 degree only
How long should the EpiPen needle be held in place when injecting
3 seconds
After removing the EpiPen needle, how long should you massage the area for
10 seconds
T/F: to know you have injected the full amount of EpiPen, there should be no liquid in the device after using
False - there may be liquid remaining in the device after injection
T/F: A second dose of EpiPen can be given in the opposite leg if needed prior to arrival of medical help
True
T/F: EpiPen CANNOT be injected through clothing
False - it can
On the NAPLEX, if a patient is allergic to PCNs, all PCN classes should be avoided, with the exception of:
Acute otitis media; use of a 2nd or 3rd gen cephalosporin in patients with non-severe PCN allergy (cefdinir, cefpodoxime, ceftriaxone, or cefuroxime)
Which medication is considered safe in patients with PCN allergies
Aztreonam
In which disease state should a pregnant person or a person with HIV & a PCN allergy be desensitized and still receive PCN
Syphilis - PCN G Benzathine (Bicillin LA)
Which drugs/classes contain a warning or CI for use in patients with sulfa allergies
Thiazide & loop diuretics Sulfonylureas Acetazolomide Zonisamide Celecoxib Darunavir
T/F: Sulfite or sulfate allergies cross react with sulfonamides
False - they do not cross react
Contrast media used in CT scans can cause
Anaphylactoid reactions and delayed skin reactions
Drugs to avoid with a peanut or soy allergy
Clevidipine
Propofol
Patients who have true allergy to eggs should avoid which drugs
Clevidipine
Propofol
Yellow Fever vaccine
T/F: if a severe reaction occurs to an influenza vaccine, regardless of which ingredient is suspected, the patient should not receive further doses of any influenza vaccine formulation
True
if egg allergy, no matter how severe, can get any flu vaccine indicated
What is the most common drug allergy in the US
PCN allergy
What is the goal of penicillin skin testing
To identify patients who are at the greatest risk of a Type I hypersensitivity reaction
Skin testing only predicts what kind of reaction
IgE-mediated
How is desensitization done
A very small dose of the medication is administered and the dose is increased in increments at regular time intervals up to the target dose
What happens if doses are missed during desensitization
The drug-free period allows the immune system to re-sensitize to the drug and serious hypersensitivity reactions could occur with subsequent doses
Desensitization should NEVER be attempted if an agent has previously caused which reactions
SJS or TEN
