Drug Allergies & Adverse Reactions Flashcards
Type A reactions
dose-dependent and predictable
Type B reactions
not dose-dependent, and not predictable. Can be influenced by patient-specific factors. Ex. drug allergies, pseudoallergic reactions, drug intolerance, idiosyncratic reactions
True drug allergies can be classified into…
4 types
Type I reactions:
immediate (within 15-30 min of drug exposure). Ex. urticaria, bronchospasm, angioedema, anaphylaxis
Type II reactions:
minutes to hours after drug exposure. Ex. hemolytic anemia and thrombocytopenia
Type III reactions:
immune-complex reactions; occur 3-10 hour after drug exposure. Ex. drug-induced lupus erythematosus (DILE)
Type IV reactions:
delayed hypersensitivity reactions; can occur anywhere from 48 hours to several weeks after drug exposure. Ex. PPD skin test for TB (peaks at 48-72 hours)
A black boxed warning (BBW) indicates a:
risk of death or permanent disability from a drug (ex. increased risk of venous thromboembolism and death from stroke with raloxifene)
Histamine is released by…
mast cells and basophils
Contraindications indicate that..
the drug cannot be used in that patients (risk outweighs the benefit)
Adverse reactions (ADRs) refer to…
undesirable, uncomfortable or dangerous effects from a drug
Risk Evaluation and Mitigation Strategies (REMS) are…
risk management plants required by the FDA for some drugs (developed by the manufacturer and approved by the FDA) Ex. clozapine REMS, iPLEDGE for isotretinoin, and REMS to reduce the misuse of long-acting opioids
Medication Guides present important adverse events that can occur with over 300 medications and should be dispensed…
with the original Rx and with each refill. Required for many individual meds and some entire classes (including anticonvulsants, antidepressants, long-acting opioids, NSAIDs, ADHD stimulants, atomoxetine)
When an ADR occurs, the Naranjo Scale is used to…
help determine the likelihood that a drug caused an ADR. A score ≥ 9= definite ADR; 5-8= probable ADR; 1-4= possible ADR; 0= doubtful ADR
Side effects, adverse events, and allergies should be reported to the FDA’s MedWatch program, also known as..
FDA’s Adverse Event Reporting System (FAERS)
The FDA can require Phase IV (post-marketing safety surveillance programs) for…
approved drugs and biologics to collect/analyze the reports to better understand the safety profile in a real-world setting
If a FDA receive enough reports that a drug is linked to a particular problem, the manufacturer can…
be required to update the labeling (ex. package insert). In especially risky cases, a drug safety alert is issued to prescribers, usually before the labeling is changed.
Oseltamivir (Tamiflu) was initially released without any warning of unusual behavior in children. The FDA received enough reports that they issued a warning to prescribed in 2006. After many more reports, in 2008, the FDA…
required the manufacturer to update the prescribing information to include a precaution about hallucinations, confusion and other strange behavior in children
Electronic medical records allow for documentation of intolerances separate from allergies. Intolerances are less serious complaints, and the drug should be avoided if possible. For example…
a patient who had stomach upset with codeine (but not hydrocodone or other drugs in the morphine class)
Opioids cause a non-allergic release of histamine from…
mast cells in the skin, causing itching and hives in some patients. Pruritus can be reduced or avoided if the patient is premedicated with an antihistamine, such as diphenhydramine
Photosensitivity can happen when sunlight reacts with a drug in the skin and causes tissue damage that looks like a severe sunburn (usually within hours of sun exposure). A type IV (delayed hypersensitivity) reaction…
can also occur with sun exposure and some meds. It appears as a red, itchy rash that can spread to areas that were not exposed to sun and occurs within days of sun exposure.
When dispensing medications that can cause photosensitivity, it is important to…
counsel the patient and/or their caregivers to limit sun exposure and to used sunscreens that block both UVA and UVB radiation
Drugs most commonly associated with photosensitivity include:
- amiodarone
- diuretics (thiazide and loop)
- methotrexate
- oral and topical retinoids
- quinolones
- St. John’s Wort
- sulfa antibiotics
- tacrolimus
- tetracyclines
- voriconazole
Other drugs that can cause photosensitivity include:
- antihistamines (1st gen)
- carbamazepine
- chloroquine
- coal tar
- fluorouracil
- griseofulvin
- NSAIDs
- quinidine
- tigecycline