Drug Allergies

Question 1

What are some examples of rashes induced by drugs?

Answer 1

1) Morbilliform
2) Hives
3) Photosensitive Reactions
4) Series Ones:

SJS/TEN, DRESS, Toxic Epidermal Necrolysis

Question 2

What are the low prevalence types of rashes caused induced by drugs? Concerns with these types of rashes?

Answer 2

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

Question 3

What is the most common form of a drug induced rash?

Answer 3

Most common form of drug induced rash

• Measles like reaction; maculopapular rash

Question 4

What are the common reasons for a morbilliform rash?

Answer 4

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

Question 5

Describe the prevalence of drug induced rashes

Answer 5

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

Question 6

Describe the clinical features of a drug eruption? How long can it take for a rash to appear?

Answer 6

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)

Question 7

Describe the prevalence morbilloiform rashes. Symptoms?

Answer 7

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

Question 8

When do morbilliform rashes develop? What area of the body is commonly affected?

Answer 8

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

Question 9

Describe the treatment of morbilliform drug eruptions?

Answer 9

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

Question 10

What is the second most common type of drug rash?

Answer 10

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

Question 11

What are some drugs that are known to cause urticarial rashes?

Answer 11

NSAID’s
ACE inhibitors
Antibiotics; especially penicillin
General ansthetics

Question 12

How can a morbilliform and a utricarial reaction be differentiated?

Answer 12

Not easy to differentiate hives and morbilliform reactions some times

Hives - Welts that move around

Morbilliform - Will not move around

Question 13

What is a common drug that can cause a rash and is likely to be labelled as an “allergy”? Reality?

Answer 13

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)

Question 14

What are the two different types of photo sensitivity drug reactions? What is the most common type?

Answer 14

Photo-toxic reactions (most common type)

Photo-allergic reactions

Question 15

Describe phototoxic reactions

Answer 15

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)

Question 16

Describe photoallergic reactions

Answer 16

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

Question 17

What are some causes of SJS?

Answer 17

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

Question 18

Is a rash a link to SJS?

Answer 18

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

Question 19

Is SJS more common than other drug-induced rashes? What is the prevalence in Canada?

Answer 19

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

Question 20

Describe Septra (trimethoprim-sulfamethoxazole) and its common adverse drug effects? Are these common?

Answer 20

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

Question 21

When does SJS occur with the causuative agent?

Answer 21

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

Question 22

What are the symptoms of SJS? Main ones to consider?

Answer 22

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

Question 23

What is a major red flag sx that can clue a pharamcists into SJS?

Answer 23

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

Question 24

Describe why identifying a case of SJS may be difficult? Example?

Answer 24

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

Question 25

Describe the severity of SJS

Answer 25

Life-threatning illness - Systemic Reaction occuring here - Involvement of the mucous membranes

Question 26

When should an individual see a physician for a skin rash?

Answer 26

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

Question 27

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?

Answer 27

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

Question 28

What do most references suggest if an individual has a rash after starting a new drug? Pharamcists role?

Answer 28

Most vreferences suggest disontinuing the new agenr - Legal over therapeutic Discontinue the agent p Contact the MD and discuss the situation

Question 29

When a pharamcist contacts a physician regarding a drug induced the rash, a physician willl....

Answer 29

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

Question 30

What are some caises of a morbiloiform rash?

Answer 30

Infections --> Measles, strep, sixth disease Drugs --> NSAIDs, antibiotics, etc.

Question 31

What are some causes of hives?

Answer 31

Infections, chemicals, latex, etc. Drugs (10%) / Foods (1%)

Question 32

Are hives a sign of a allergu?

Answer 32

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

Question 33

When can drug induced rash occur?

Answer 33

Can occur on the first dose or after many doses - Rashes may develop up to 6 weeks after starting certain types of medications

Question 34

Describe the prevalence of drug induced rashes?

Answer 34

Occurs in less than 5% of patients

Question 35

What should be done when an individual develops a drug induced rash?

Answer 35

Discontinue the agent is the most common move --> Legal Reasons Most reactions are mild and clear in a few days

Question 36

Describe the resolvement of a drug induced rash?

Answer 36

Can see mild skin peeling as the rash resolves

Question 37

What are some common agents that may lead to a drug induced rash?

Answer 37

Antibioticcs, NSAIDs, and ACEi - Never say rash when talking about side effects of NSAIDs

Question 38

What can happen at the next exposure of the drug?

Answer 38

No reaction Same Reaction Worse Reaction --> Rare scenario If a true drug allergy, will not get that drug anymore

Question 39

Describe the adverse effects of ibuprofen and its risk of a rash

Answer 39

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

Question 40

Describe a drug-induced rash with amoxicllin

Answer 40

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

Question 41

Describe a penicillin allergy

Answer 41

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

Question 42

Describe a pharmacists ideology regarding penicllin allergies:>

Answer 42

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

Question 43

What are some of the reasons an individual may believe that they are allergic to penicllin?

Answer 43

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

Question 44

What is a misconception that is common in the medical field?

Answer 44

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

Question 45

If anaphylaxis was suspected, what would be required if a rash was presnet?

Answer 45

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

Question 46

Describe the symptoms of anaphylaxis in regards to a drug induced rash

Answer 46

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

Question 47

How can a drug allergy be managed?

Answer 47

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"

Question 48

Use of 2nd gen anti-histamines in drug induced reactions

Answer 48

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

Question 49

What is a concern in elderly regarding sickness? Rash?

Answer 49

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

Question 50

Recap the major points of drug induced rashes

Answer 50

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