Introduction
They are common
Only about 2% of all drug induced skin reactions are severe and few are very fatal
They account for 30% of all reported
... [Show More] ADRs
They affect patients’ self confidence and future compliance with medication
Diagnosis
It is often difficult to diagnose these ADRs because:
Same drugs may produce different reactions in different patients
Almost any drug can affect the skin
Unrelated drugs can produce the same skin reaction
Many reactions cannot be distinguished from naturally occurring eruptions
Patient history taking and examination
Check that the reaction is not due to a specific skin condition
Take accurate medication history including OTC, herbal and homeopathic preparations and any injections. Record both generic and brand names of medicines
History.....
Ask patient of any history of sensitivity or allergy
Ascertain the time course of eruption in relation to drug use
Note whether the appearance of the rash is typical of any classic drug induced eruption
Treatment
Withdraw offending drug
In some cases dose reduction is sufficient
In photosensitive reactions the drug may be continued but the patient should be advised to avoid the sun and use sunscreen
Rx
In mild cases the rash may be treated with oral antihistamines
In severe cases which are life threatening, early diagnosis with early recognition and withdrawal of all causative agents is essential.
COMMON DRUG INDUCED DISORDERSErythrematous/ Exanthematous reactions
Most common type of drug induced skin reaction
The rash is characterised by erythrema (reddening) of the skin
It may be mobiliform (resembling measles) or maculopapular ie consisting of macules and papules
Macules are flat areas while papules are raised lesions less than 1 cm diameter
Erythrematous...
The rash is bright red in colour
The skin may feel hot, itchy or burning
The whole skin surface may be involved but the face is often spared
Erythrematous...
The rash may disappear even with continuation of drug, but if its itchy, it is unlikely to disappear
In severe cases erythroderma may follow, where erythrema persists with scaling, lymphadenopathy, pyrexia, thirst and shivering, with heat and fluid loss from the skin
Mechanism
Usually allergy but many other mechanisms may be involved
Allergic reactions can occur early or late in therapy
Early reactions present within 2-3 days of drug administration and usually occur in previously exposed patients
Mechanism
Late reactions can present 9 days after therapy and can occur as late as 3 weeks after initiation of therapy and continue 3 weeks after cessation of therapy
Drugs associated with erythrematous reactions
Treatment:
Withdraw drug
Treat associated itching with antihistamines
Erythroderma and exfoliative dermatitis
Erythroderma is a widespread erythrematous rash
Exfoliative dermatitis is desquamation of skin
It is usually severe
Systemic symptoms like hypothermia, fluid and electrolyte loss and infection are present
Drugs that cause erythroderma and exfoliative dermatitis
Pruritis
Itching
Drugs can induce pruritis on their own or as a result of other cutaneous reactions
The mechanism of causation of pruritis is unknown for most drugs but it may be central or peripheral or both
Severe pruritis can cause lesions [Show Less]