Drug Allergies Flashcards
What is an adverse drug reaction?
Adverse drug reaction is a term that encompasses all unintended pharmacological effects of a drug when it is administered correctly and used at recommended doses. They are typically dose-related and ADR severity increases with higher doses/reduced clearance
How can adverse drug reactions be categorized?
ADRs are categorized into two types: predictable (Type A) and unpredictable (Type B) reactions
What are Type A reactions?
Type A are dose-dependent, related to the known pharmacologic actions fo the drug, can occur in any patient and can range from mild to severe
*Type A reactions are the most common and account for an estimated 80% of ADRs
What are type B reactions?
Type B reactions are generally not dose-dependent, are unrelated to the pharmacological actions of the drug and can be influenced by patient-specific factors.
What are some examples of type B reactions?
Drug allergies, pseudoallergic reactions, drug intolerances, idiosyncratic reactions
What does a drug allergy refer to?
Drug allergy refers to an immune-mediated response to a medication or excipient (inactive ingredient) and are classified into four types
What is a type I hypersensitivity reaction?
IgE mediated response and immediate (within 60 minutes of drug exposure). Severity ranges from minor local reactions to severe systemic reactions (e.g. urticaria, bronchospasm, angioedema and anaphylaxis)
What is a type II hypersensitivity reaction?
Antibody-mediated; occur several days (usually 5-8 days) after drug exposure (e.g. hemolytic anemia and thrombocytopenia)
What is a type III hypersensitivity reaction?
Immune-complex reactions; occur 1 or more weeks after drug exposure (e.g. drug-induced lupus erythematosus)
What is a type IV hypersensitivity reaction?
Cell-mediated or delayed hypersensitivity reactions; can occur anywhere from 48 to several weeks after drug exposure (e.g. PPd skin test for tuberculosis, SJS)
What is a boxed warning?
A boxed warning indicates a risk of death or permanent disability rom a drug
What are contraindications?
Contraindications indicate that the drug cannot be used in that patient. The risk will outweigh any possible benefit
What do warnings and precautions include?
Warnings and precautions include serious reactions that can result in death, hospitalization, medical intervention, disability or teratogenicity
What are adverse reactions?
Adverse reactions refer to undesirable, uncomfortable or dangerous effects from a drug. The risk-benefit assessment is patient-specific
What is risk evaluation and mitigation strategies (REMS)?
REMS are risk management plans required by the FDA for some drugs. They are developed by the manufacturer and approved by FDA to ensure the benefits of a drug outweigh the risks
What can a REMS program include?
REMS programs can include a medication guide or patient package insert, communication plan, elements to assure safe use or an implementation system
What are medication guides?
Medication guides present important adverse events that can occur with over 300 medications. MedGuides are FDA-approved patient handouts that are written in non-technical language and are considered part of the drug’s labeling. If a medication has a MedGuide, it should be dispensed with the original prescription and with each refill
What scale can be used if ADR occurs?
When an ADR occurs, the Naranjo Scale can help determine the likelihood that a drug caused the adverse drug reaction
What do the scores on the Naranjo scale represent?
A score > 9 = definite ADR; 5-8 = probable ADR; 1-4 = possible ADR; 0 = doubtful ADR
What is the pharmacist role when patients report an adverse drug reaction?
Pharmacists must ask the right questions in order to determine whether an adverse reaction is an intolerance or drug allergy
Where should side effects, adverse events and allergies be reported?
Side effects, adverse events and allergies should be reported to the FDA’s MedWatch program, which is called the FDA Adverse Event Reporting System (FAERs) and provides a central collection point for problems caused by drugs, biologics, medical devices, some dietary supplements and cosmetics
What is the purpose of Phase IV trials (post-marketing safety surveillance programs)?
The FDA can require phase IV trials for approved drugs and biologics, to collect and analyze the reports and better understand the drug safety profile in a real-world setting. Post-marketing reports also help identify side effects that occur less frequently
What can be done if the FDA receives enough reports that a drug is linked to a particular problem?
If the FDA receives enough reports that a drug is linked to a particular problem, the manufacturer can be required to update the labeling. In especially risky cases, a drug safety alert is issued to prescribers, usually before the labeling is changed
Is an ADR of stomach upset/nausea considered an intolerance or an allergy?
It is not an allergy and should not prevent drugs in the same class from being used. This is more accurately categorized as an intolerance
What kind of non-allergic adverse effect can opioids cause and how can it be treated?
Opioids cause a non-allergic release of histamine from mast cells on the skin, causing itching and hives in some patients. This type of reaction, if not severe. can be reduced or avoided if the patient is premedicated with an antihistamine
What is photosensitivity?
Photosensitivity can occur when sunlight reacts with a drug in the skin and causes tissue damage that looks like a severe sunburn on sun-exposed areas; this occurs within hours of sun exposure. A type IV reaction can also occur with sun exposure and some medications
How does photosensitivity present?
It appears as a red, itch rash that can spread to areas that were not exposed to sun and occurs within days of sun exposure
What are some key drugs that can cause photosensitivity?
Amiodarone, diuretics, Methotrexate, oral and topical retinoids, quinolones, St. John’s Wort, Sulfa antibiotics, Tacrolimus, Tetracyclines, Voriconazole
What is a key counseling point when dispensing a medication with photosensitivity?
It is important to advise the patient and/or their caregivers to limit sun exposure and to use sunscreens that block both UVA and UVB radiation
What is thrombotic thrombocytopenic purpura (TTP)?
TTP is a blood disorder in which clots form throughout the body. The clotting process consumes platelets and leads to bleeding under the skin and the formation of purpura (bruises) and petechiae (dots on the skin)
*TTP can be fatal and should be treated with plasma exchange
What are some key drugs associated with TTP?
Oral P2Y12 inhibitors, Sulfamethoxazole
What are some examples of severe skin reactions?
Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) and drug reaction with eosinophilia and systemic symptoms (DRESS)
What are key drugs that can cause severe skin conditions?
Abacavir, Allopurinol, Carbamazepine, Ethosuximide, Lamotrigine, Modafinil, Nevirapine, Penicillins, Phenytoin, Sulfamethoxazole
What is SJS and TEN?
SJS and TEN involve epidermal detachment and skin loss that is equivalent to third degree burns. SJS and TEN are commonly classified by the percent of skin detachment
When does SJS and TEN generally occur?
SJS and TEN generally occur 1-3 weeks after drug administration and almost always more than 72 hours after drug administration
How does SJS and TEN present?
These reactions can result in severe mucosal erosions, a high body temperature, major fluid loss and organ damage
What is the key to treat SJS and TEN?
The key to treating both is to stop the offending agent as soon as possible. In addition, patients will receive fluid and electrolyte replacement, wound care and pain medications. Systemic steroids are contraindicated in TEN, but may be used in SJS, thought benefit is controversial. Due to the severity of the mucosal involvement, antibiotics are often necessary to prevent or treat an infection
How does DRESS typically present?
DRESS can include a variety of skin eruptions accompanied by systemic symptoms such as fever, hepatic dysfunction, renal dysfunction and lymphadenopathy, but rarely involves mucosal surfaces
What does treatment for DRESS consist of?
Treatment consists of stopping the offending drug, although symptoms may continue to worsen for a period of time after the drug has been discontinued
What needs to occur for a true drug allergy to occur?
For a true drug allergy to occur, the person must have taken the drug previously. Initial exposure will cause sensitization, which primes the body to release excessive histamine the next time the individual is exposed to the drug. The result is a Type I hypersensitivity reaction.
What is an anaphylactoid reaction?
It is not IgE-mediated, but the clinical appearance and treatment are similar to that of anaphylaxis
How can a reaction without breathing difficulty sometimes be treated?
A reaction without breathing difficulty can sometimes be treated by stopping the offending drug
What are some examples of medications that can be used to treat allergic reactions?
- Antihistamines can be used to counteract the histamine release the causes itching, swelling and rash
- Systemic steroids, and sometimes NSAIDs, can be used to decrease swelling
- Severe swelling may necessitate a steroid injection
- Epinephrine is used to reverse bronchoconstriction if the patient is wheezing or has other signs of trouble breathing
What is anaphylaxis?
Anaphylaxis is a severe, life-threatening allergic reaction that usually happens within 1 hour of drug exposure, but may occur much more rapidly. Anaphylaxis can occur after an initial exposure and subsequent immune response, but some drugs can cause anaphylaxis with the first exposure
How does anaphylaxis typically present?
A patient experiencing anaphylaxis may have generalized urticaria (hives), swelling of the mouth and throat, difficult breathing or wheezing sounds, abdominal cramping or hypotension (which can cause dizziness, lightheadedness or loss of consciousness)
What should the patient and family be counseled on if anaphylaxis occurs?
An anaphylactic reaction requires immediate emergency medical care. The patient or family should be instructed to call 911 if anaphylaxis occurs.
Describe anaphylaxis treatment
Anaphylaxis treatment includes epinephrine injection +/- diphenhydramine +/- steroids +/- IV fluids. To avoid blocking the airway, nothing should be placed under the head or in the mouth
What should patients who have anaphylactic reactions have with them?
Patients who have had such a reaction should carry a single-use epinephrine auto-injector as they may be at future risk
*The patient’s emergency kit should also include emergency contact information and diphenhydramine tablets which should be taken only if there is no tongue/lip swelling
How is the EpiPen available as?
They are generally available as epinephrine 1 mg/mL in dosages of 0.3 mg (adult dose) or 0.15 mg (pediatric dose for patients 15-30 kg). Symjepi is only available in 0.3 mg (indicated for 30 kg and up) and Anvi-Q is also available in 0.1 mg (for patients weighing 7.5-14 kg)
What are some key counseling points for all epinephrine auto-injectors?
- Tell family, caregivers and others where the epinephrine auto-injector is kept and how to use it, as you may not be able to speak in an allergic emergency
- It is important to keep the thumb, fingers and hand away from the needle end of the device, as accidental injection can cause vasoconstriction and necrosis
- When injecting an uncooperative child, hold leg firmly to avoid bending or breaking the needle
- Skin infections can occur. Report any prolonged redness, swelling, warmth or tenderness at the injection site
What are some key counseling points specific to Symjepi?
- Pull off the cap, holding the syringe with the fingers (avoiding the needle)
- Inject in the middle of the outer thigh, hold needle firmly in place on the thigh for two seconds, then massage area for 10 seconds
- After injection, slide the safety guard over the needle
What are some key counseling points for Anvi-Q?
Pull off the outer case, then follow the voice instructions to administer. Hold the needle firmly in place on the thigh for five seconds
What are the two classes of medications that cause the most drug allergies?
Penicillins and sulfonamides
What is the most reliable way to determine if a person is truly allergic to a drug?
Patch testing by an allergist
What should be assumed if someone is allergic to one of the penicillins?
Anyone who is allergic to one of the penicillins should be presumed to be allergic to all penicillins and should avoid the entire group, unless they have been specifically evaluated by a healthcare provider
Can a person with a penicillin allergy take cephalosporins?
People with a history of penicillin allergy have a small risk of also having an allergic reaction to a cephalosporin or carbapenem. Risk of cross-reactivity is low, but it is prudent on the NAPLEX to avoid any beta-lactam with a stated allergy to another, unless there is an acceptable alternative agent
What is the exception on NAPLEX to avoid cephalosporin in patients with a stated penicillin allergy?
A notable exception is in acute otitis media. The AAP recommends use of 2nd or 3rd generation cephalosporins in patients with non-severe penicillin allergy, due to toxicities and decreased efficacy of alternative AOM therapies in children
What monobactam is considered safe in patients with penicillin allergies?
Aztreonam
What should be done in a pregnant patient or certain patients who have HIV who have a penicillin allergy and syphilis?
- Must test, and if positive, temporarily desensitize
- Penicillin is the only acceptable treatment in these patients
What medications can cause sulfa reaction?
Sulfa reactions are most commonly reported with sulfamethoxazole. Other drugs that should be avoided in these patients include sulfasalazine, sulfadiazine and sulfisoxazole
Which medications have warnings regarding patients with sulfa allergies?
The package labels for non-arylamine sulfonamides, sulfonylureas, acetazolamide, as well as cidofovir, darunavir, fosamprenavir and tipranavir contain warnings or contraindications for use in patients with a sulfa allergy, although they usually do not cross react with a sulfamethoxazole allergy
What medications have a low risk of cross reactivity with sulfamethoxazole?
The risk of cross-reactivity with sulfamethoxazole, thiazides and loop diuretics is very low.
*Recognize the possible interaction
What class of medications does not interact with sulfonamides?
Sulfite or sulfate allergies do not cross react with sulfonamides
What are the symptoms of drug sensitivity of NSAIDs?
A drug insensitivity can cause rhinitis, mild asthmatic-type reactions or skin reactions
What are symptoms of a true allergy of NSAIDs?
The patient will experience uritcaria, angioedema and occasionally anaphylaxis
What can contrast media cause?
Contrast media can cause anaphylactoid reactions and delayed skin reactions. Systemic steroids and antihistamines can be used to prevent reactions if contrast media is needed in a patient who has had a prior reaction
Why is it important for the pharmacist to be aware if a patient has a peanut allergy/
Peanuts and soy are in the same family and can have cross-reactivity. Soy is used in some medications
What is an important counseling point for parents of children who have peanut allergies?
Parents of children with peanut allergies should be CPR-trained and have ready access to an epinephrine auto-injector
What are some drugs to avoid with a peanut or soy allergy?
Clevidipine, propofol and progesterone
What medications should be avoided if a patient has a true allergy to eggs?
Clevidipine, propofol or the yellow fever vaccine
What is recommended for the influenza vaccine with patients who have an egg allergy?
ACIP states that even patients who have had more severe symptoms when consuming eggs can receive any indicated inactivated vaccine
*Flublok, which is made using recombinany techniques and contains no egg protein, is one option in patients with severe egg allergy
What should you do if a patient has a severe reaction to an influenza vaccine?
If a severe reaction to an influenza vaccines occurs, regardless of which ingredient is suspected, that patient should not receive further doses of any influenza vaccine formulation
What is the goal of penicillin skin testing?
The goal of penicillin skin testing is to identify patients who are at the greatest risk of type I hypersensitivity reaction if exposed to a systemic penicillin
What is in the penicillin skin test?
The penicillin skin test uses the components of penicillin that most often cause an immune (allergic) response. Pre-pen contains the major determinants of penicillin allergy and is used with very dilute solutions of penicillin G
How is the penicillin skin test performed?
A step-wise skin test is performed: a skin prick test followed by intradermal testing
What does a localized reaction around the pre-pen or penicillin G site indicate?
It indicates a high risk of a reaction to systemic penicllin and the patient should not receive it
What does it mean when a patient has a negative skin test?
A patient with a negative skin test can be considered to be at the same risk as a patient in the general population who hoes not report a penicillin allergy
What does the penicillin skin testing predict?
Skin testing only predicts an IgE-mediated reaction
What is the exception to when a medication cannot be re-challenged despite skin test results?
Regardless of skin test results, a patient should never be re-challenged with an agent that caused SJS or TEN
What is desensitization?
Desensitization is a step-wise process that begins by administering a very small dose of the medication and then incrementally increasing the dose at regular time intervals up to the target dose
What is the goal of desensitization?
This modifies the patient’s response to the medication and temporarily allows safe treatment
What is required with the desensitization process?
The desensitization procedure must take place in a medical setting where emergency care can be provided if a serious reaction occurs. Treatment with the agent must start immediately following the desensitization procedure and must not be interrupted
What happens if doses are missed during the desensitization period?
If doses are missed, the drug-free period allows the immune system to re-sensitize to the drug and serious hypersensitivity reactions (including anaphylaxis) could occur with subsequent doses
When should desensitization never be attempted?
Desensitization should never be attempted if an agent has previously caused SJS or TEN
