Drug Allergies Flashcards
What are some types of drug-induced drugs?
Morbilliform (“measles-like”)
Hives
Photo-sensitive reactions
Severe rashes (SJS/TEN, DRESS, Toxic Epidermal Necrolysis)
What are morbilliform drug rashes?
They are the most common form of drug rash (up to 90% of cases). It is a maculopapular rash and can be caused by all types of drugs, but antibiotics are the most common group. The presentation of a morbilliform rash is pretty vague in terms of cause, but most rashes of this type in adults are usually caused by a reaction to drugs
How many new prescriptions result in drug reactions?
About 2% of new prescriptions cause a drug reaction. In this 2%, 95% of rashes are morbilliform.
Most reactions are to drugs like penicillins, cephalosporins, sulfonamide, allopurinol, NSAIDs
How does a morbilliform rash develop?
On first exposure to a new drug, morbilliform rashes usually take 1-2 weeks after starting drug therapy to erupt. Rashes develop on subsequent exposures in 1-3 days.
Morbilliform rashes usually first appear on the trunk and then spread to the limbs and neck. The distribution of a morbilliform rash is bilateral and symmetrical
Sometimes the rash is accompanied by a fever and itch, tricking HCPs to think infection when its actually a drug reaction
How to treat morbilliform rashes?
The most important thing to do is determine which drug is causing the reaction and discontinue it.
Follow this action with the following:
Monitor the patient carefully in case of complications
Apply emollients and potent topical steroid creams
Consider wet wraps for very red, inflamed skin
The rash should begin to improve within 48 hours and clear up within 1-2 weeks
Are antihistamines effective in treating morbilliform rashes?
They are not very helpful, but they are given to patients regardless
Are drug rashes very itchy?
No, drug rashes generally do not tend to cause any other symptoms besides their appearance, though some are accompanied by itching or tenderness. The itch is far less compared to hives.
What should pharmacists do if morbilliform rashes form blisters or pus-filled lesions?
This needs MD referral for closer inspection as it could be something more worrisome than a drug-induced rash
What are urticarial rashes?
Urticaria is another word for hives. Hives are the second most common type of drug rash (5-10% of drug reactions). Hives are small, pale red pumps that can form larger patches. Hives also tend to be very itchy, unlike morbilliform rashes.
What is the difference between phototoxic and photoallergic reactions?
Phototoxic reactions:
The drug may become activated following exposure to sunlight and cause damage to the skin. The skin appears like a sunburn due to the irritation caused by the activated drug. A phototoxic reaction typically clears up once the drug is discontinued and has been cleared from the body, even after re-exposure to light
Photoallergic reactions:
The drug’s physical structure is altered by UV light in a way that the immune system sees it as an antigen. The inflammatory response kicks in and causes a rash that somewhat resembles eczema.
What is Stevens-Johnson Syndrome (SJS)?
SJS is a rare disease, affecting 1 to 2 per million people yearly. It is characterized by painful skin rash in addition to flu-like symptoms. The rash further develops into large blisters that eventually leave painful sores after bursting. Rashes in SJS usually involve the skin, lips, mouth, eyes, and genitals
SJS is life-threatening, so hospitalization is needed
When should patients see a physician regarding any rash?
High temperature indicating an infection or allergic reaction
The rash is very painful
Fluid-filled blisters or open sores
Signs of infection, such as pus, swelling, crusting, warmth, or extreme pain
If breathing becomes difficult, your throat tightens or your tongue is swelling, these are signs of an anaphylactic reaction
Do people with drug-induced rashes have other symptoms?
No, the only symptoms present are for the condition being treated
Are most drug-induced rashes allergic?
No, most are simple rashes (10x more rashes vs. true allergies), but we still give an EpiPen especially if things like angiodema are present (legalistic requirements)
When should drugs that cause reactions be discontinued?
It really depends on how involved the rash has become.
In low level rashes, we advise patients to power through the treatment cycle
