Drug Allergies Flashcards
What are some examples of rashes induced by drugs?
1) Morbilliform
2) Hives
3) Photosensitive Reactions
4) Series Ones:
SJS/TEN, DRESS, Toxic Epidermal Necrolysis
What are the low prevalence types of rashes caused induced by drugs? Concerns with these types of rashes?
Photosensitive - Low level; not a prevalent player
Problem - SJS, TENs and DRESS
–> Rare; however, serious
Legal over therapeutic
Prevalence of SJS and its risk gets blown out of proportion
What is the most common form of a drug induced rash?
Most common form of drug induced rash
- Measles like reaction; maculopapular rash
What are the common reasons for a morbilliform rash?
A morbilliform rash in adults tends to usually be due to a drug
In a child, a morbilliform rash is more liekly to be viral in origin
Describe the prevalence of drug induced rashes
About 2% of prescription new drugs cause a drug eruption rash
ABout 95% of these are mobilliform drug eruptions
Drug induced rashes are not that common
- MAy not be the most ideological factor
Describe the clinical features of a drug eruption? How long can it take for a rash to appear?
Drug induced rashes tend to cause no other symptoms besides their appearence, although some are accompanied by itching and tenderness
- Far less itchy than hives
It can take a drug up to two weeks yo cause a rash (this makes linking the drug to the rash difficult)
Describe the prevalence morbilloiform rashes. Symptoms?
Most common type of drug induced rash making up to 90% of cases
Marked by small lesions on redenned skin –> lesions can be flat or raised
May also notice blisters and pus-filled lesions
- If this happens, all pharmacists would be worried and would suspect something far more worrisome than a simple-drug induced rash - Done Here
When do morbilliform rashes develop? What area of the body is commonly affected?
Morbilliform rash usually appears 1-2 weeks after starting a drug, but it may occur up to 1 week after stopping the drug
It is very rare for a drug that has been taking for months and years to cause a morbilliform drug eruption
Morbilliform drug eruption usually first appears on the trunk and then spreads to the limbs and the neck
Maculopapular Rash
Describe the treatment of morbilliform drug eruptions?
Most important thing is to identify the causative drug and if possible stop it (Most common suggestion)
ANti-histamines are often prescribed but are not helpful
If 100% an allergy, educate patient on the danger of re-exposure to the same medication; however, if not known if true allergy this is overly cautious
If the drug is important, more likely to stick the rash out as rash will go way - A lot of the reactions are not allergic in nature
Assuming 100% allergic –> legal aspect over therapeutic
What is the second most common type of drug rash?
Utricaria/Hives
Second most common type of drug rash. 9Distanr second place)
- Small, pale red bumps that can form larger patches and are very itchy
Can be hard to differentiate between hives and morbilliform reactions
What are some drugs that are known to cause urticarial rashes?
NSAID’s
ACE inhibitors
Antibiotics; especially penicillin
General ansthetics
How can a morbilliform and a utricarial reaction be differentiated?
Not easy to differentiate hives and morbilliform reactions some times
Hives - Welts that move around
Morbilliform - Will not move around
What is a common drug that can cause a rash and is likely to be labelled as an “allergy”? Reality?
Antimicrobial sulfonamides are the second most frequent cause of allergic drug reactions
–> Less than 5%; often benign
- Will be labelled as a sulfa allergy
Illness that the antibiotic is being used to treat is more likely to be causing the reaction than the drug itself - Cannot be sure (legal)
What are the two different types of photo sensitivity drug reactions? What is the most common type?
Photo-toxic reactions (most common type)
Photo-allergic reactions
Describe phototoxic reactions
Most common type of photosensitivity reaction
- Skin reaction occurs minutes to hours after exposure to agent and light
- Appears as an exaggerated sun burn reaction (swelling and reddening) - looks like a sunburn
- Vesicles and bullae may occur in svere reactions
- The reactions is limited to sun-exposed skin
- Non-toxic rash
- Less common - skin may change colour (e.g. blue-green with amiodarojne)
Describe photoallergic reactions
Eczemayous itchy type reaction that occurs 24-72 hours after exposure to an agent
May spread to areas that have not been sun exposed
Hyperpigmentation does not occur
Drug and sun together - Drug allergy induced by the sun - Splotchy appearence
What are some causes of SJS?
More thna 100 drugs can cause SJS, most common are:
1) Medicines for gout especially allopurinol
2) Pain relievers such as acetaminopgen, ibuprofen and naproxen
3) Sulf antibiotics –> BActrim and septra
4) Medicines used to treat seizures and/or mental illness
Is a rash a link to SJS?
No
- Rash is not linked to the dvelopment of SJS
Morbiliform and haves reactions happen 3% of the time
Is it a pre-cursor to anaphylaxis? Unlikley; however, need to stop the drug as legal over therapeutic
Is SJS more common than other drug-induced rashes? What is the prevalence in Canada?
A drug induced rash (morbiliform and hives) is far more common than SJS
In Canada, SJS/TEN is a rarer disease that affectes 1-2 mkillion people per year
Describe Septra (trimethoprim-sulfamethoxazole) and its common adverse drug effects? Are these common?
Gastrointestinal - 3-4% –> Nauseau, vomitting, annorexia
Dermatologic/Immunologic –> 3-4%
- Sensitivity reactions (utricaria, rash)
When mild-moderate rashes occur, it is usually after 7-14 days of therapy
These are usually erythemous, maculopapular, morbiliform and/or pruritic
When does SJS occur with the causuative agent?
The typical course of SJS begins within 8 weeks (usually 4 to 30 days) following the first exposure to the causative agent
Only in very rare cases where an inadvertent rechallenge occurs do symptoms appear within hours
What are the symptoms of SJS? Main ones to consider?
Initial:
Skin pain is the most common symptom of SJS
Flu-like symptoms are usually also presnet during the intial stages and may include:
- Malaise
- High temperature of 38 C and above
- Headache
- Joint PAin
- Cough
After a few days a rash appears, which consisrts of individual blemishes that may look like a target - darker in the middle and lighter on the outside
The rash isn’t usually itchy, and spreads over a number of hours or days
Large blisters develop on the skin, which leave painful sores after bursting
What is a major red flag sx that can clue a pharamcists into SJS?
Skin pain hsould not be occuring with hives, and morbilliform
Start hearing skin pain in addition to what is going on –> REd Flag
starts to look like necrotizing fascitis
Condition is not causing SJS; the drug is causing it
Describe why identifying a case of SJS may be difficult? Example?
The drug was given for a reason
Ibuprofen
- Could be given to an individual with flu like symptoms, feeling unwell, a headache and some fever
- QUite similar to the early symptoms of SJS
- Since SJS is rarer, most of us would keep attributing them t the intial issue and not the drug
Even the start of a rash would make us think of a morbiliform reaction, not SJS
But in seeing SKin pain, then the rash strating to look atypical, one might start to suspect SJS
Describe the severity of SJS
Life-threatning illness
- Systemic Reaction occuring here
- Involvement of the mucous membranes
When should an individual see a physician for a skin rash?
Most skin reactions are not l9ife-thretning
If you experience any of the following sx, see MD:
1) Covering the entire body
2) Rash is very painful
3) Fluid filled blisters or open sores
If your breathing becomes difficut, your throat tightens or your tongue is swelling, it’s a clear sign ypour skin rash is due to an allergic reaction –> EMERG
An individual has a new rash from a drug started a week ago, what is the rash likely to be and what may be causing it?
If due to a drug, the reaction will most often be morbiliform in appearence
If the person was also sick in the last few days, that could be the reason for the rash and not the drug
–> Especially in kids - often the virus
- 95% morbiliform, 5% hives
What do most references suggest if an individual has a rash after starting a new drug? Pharamcists role?
Most vreferences suggest disontinuing the new agenr
- Legal over therapeutic
Discontinue the agent p Contact the MD and discuss the situation
When a pharamcist contacts a physician regarding a drug induced the rash, a physician willl….
MD will decide how important it is to re-visit that agent OR make a change
An anticonvuslant may get different attention than an antibiotic
What are some caises of a morbiloiform rash?
Infections –> Measles, strep, sixth disease
Drugs –> NSAIDs, antibiotics, etc.
What are some causes of hives?
Infections, chemicals, latex, etc.
Drugs (10%) / Foods (1%)
Are hives a sign of a allergu?
Hives are generally not a sign of an allergy
Hives can be a sign of allergy as a precursor to anaphylaxis; however, most are not a sign of an allergy
When can drug induced rash occur?
Can occur on the first dose or after many doses
- Rashes may develop up to 6 weeks after starting certain types of medications
Describe the prevalence of drug induced rashes?
Occurs in less than 5% of patients
What should be done when an individual develops a drug induced rash?
Discontinue the agent is the most common move
–> Legal Reasons
Most reactions are mild and clear in a few days
Describe the resolvement of a drug induced rash?
Can see mild skin peeling as the rash resolves
What are some common agents that may lead to a drug induced rash?
Antibioticcs, NSAIDs, and ACEi
- Never say rash when talking about side effects of NSAIDs
What can happen at the next exposure of the drug?
No reaction
Same Reaction
Worse Reaction –> Rare scenario
If a true drug allergy, will not get that drug anymore
Describe the adverse effects of ibuprofen and its risk of a rash
Allergic –> Incidence less than 1% –> Anaphylaxis
Dermatologic –> 3-9% –> MAculopapular rash pruritis (1-3%), les sthan 1% (utricaria)
10% will get a rash from Ibuprofen, anaphlaxis is 1%
–> 10 fold increase as an exqample
Describe a drug-induced rash with amoxicllin
A morbiliform, erthymeous, urtricraial rash may occur
A maculopapular rash may occur in some patients after 3-14 days of therapy with amoxicllin (not a drug allergy)
–> trunk and then periphery
The rash will subside after 1-2 weeks with continued tx or after 1-7 days if the drug is disontinued
Rash < 10% - Amoxicillin rash is more common during a viral illness and should not be consiodered an allergy –> Rash is up to 10-fold more common in people with HIV infection, and extemely common in mono
Describe a penicillin allergy
Penicillin is the most commonly reported allergy
–> 9 out of 10 patients are not truly allergic
Most patients will lose their penicllin allergy after 10 years
Describe a pharmacists ideology regarding penicllin allergies:>
Only 10% of those people are truly penicllin allergic
9/10 people who think they have a penicllin allergy are avoiding it for no reason and can tolerate penicllin-based antibiotics
Evn in people witha documented allergy to penicllin, only 20% are still allergic 10 years after their iniyial allergic reactio
What are some of the reasons an individual may believe that they are allergic to penicllin?
People might believe they are allergic to penicllin for a variety of resons:
1) Side effects such as nauseau and diarhhea were often confused with allergic reactiobs
2) Symptoms of the infection being treated, such as a rash, could be considered an allergic reaction
3) Allergy reported years ago, perhaps ub childhood, has settled down but the perception of an allergy remained
What is a misconception that is common in the medical field?
RAsh = Allergic RAsh
Often combine them when this not true –> RAsh is only one system –> When anotehr system become sinvolved thats when we begin to worry
Rash is just one system and isnt enough to be an allergic reaction
Rash does not mean anaphylaxis
If anaphylaxis was suspected, what would be required if a rash was presnet?
Rash plus involvement of a second system
Anaphylaxis woulod likely develop just seconds after exposure to the allergen –> Swelling of airway, inability to breathe, sudden and severe drop in blood pressure
Describe the symptoms of anaphylaxis in regards to a drug induced rash
SIgns and symptoms of anaphylacis include:
Skin RAsh - Usually first visible sx of anaphylaxis and usually appears on the skin adn gets red
–> Rash often alters skin texture, leading to roughness or scaling –> ONLY ONE SYSTEM
Rapid and weak pulse
N/V
How can a drug allergy be managed?
If allergic to drug - D/c
Anti-histamines - USe 2nd generation antihistamunes
Corticosteroids
Tx of Anaphylaxis - EPipnephrine
Drug rechallenges are rare –> ANti-epileptics often require rgem
Rare to say to say to someone “you have a drug allergy”
Use of 2nd gen anti-histamines in drug induced reactions
Relieve symptoms associated with hives or morbiliform drug eruption
There is a debate on the value of anti-histamines for drug-related rashes, but if one is used, 2nd generation antihistamines are the choice
What is a concern in elderly regarding sickness? Rash?
Double Sickening
When someone’s symptoms worsen again after they initially seem to be recovering from a cold
- RED FLAG
- ALso a red flag for SJS –> also red flag: painful skin
Recap the major points of drug induced rashes
Generally other symptoms will not be presnet
–> Except for what the drug was given for and maybe some itch
ADR = 2%
The majority do not move on in sverity
Most are not an allergy –> legal trumps therapeutic
Will likely discontinue the agent with large vo,lume (e.g. trunk) and nnot if isolated (e.g. just on hand)
Children with respiratory infections… add on a new drug… now a rash
–> Most liekly due to the infection
