Drug Induced Skins Reactions

Question 1

What is an allergic reaction?

Answer 1

Independent of dose and may persist long after drug has been stopped - more severe if drug given again

Question 2

What is a toxic reaction?

Answer 2

Depends on dose - reactions subside when drug is stopped

Question 3

What causes drug induced skin reactions?

Answer 3

1. Genetic factors
2. Patients with hepatic, renal, SLE and AIDs - increased risk
3. Route of administration

Question 4

How would you diagnose drug induced skin reactions?

Answer 4

Timing of skin reactions - more than one drug makes it difficult

Question 5

What is an erythematous reaction?

Answer 5

1. Erythema - maculopapapular (rash with both raised and flat parts) or mobiliform (measle like rash)
2. Affects whole skin except face usually
3. Cause skin to become red, hot, burny and itchy
4. Most common

Question 6

What drugs cause erythematous skin reaction?

Answer 6

1. Penicillins
2. Cephalosporins
3. Sulphonamides
4. Thiazides
5. Gold
6. Furosemide
7. Anti TB drugs
8. Phenothiazines

Question 7

What is a fixed drug eruption?

Answer 7

1. An erythematous, dusky purple round or oval lesion with blisters or vesicles
2. Initially one lesion - then others
3. Appears within 24 hours of ingestion
4. Commonly affects hands , feet, penis, perinatal area but can be anywhere
5. Site is fixed
6. Drugs are the sole cause

Question 8

What drugs caused a fixed drug eruption?

Answer 8

Sulphonamides and barbiturates

Question 9

What is acute uticaria and angiodema?

Answer 9

Nettle rash - 36 hours after ingestion

Angiodema - vascular reaction causing increased permeability and fluid leakage

Stop drug and give antihistamine

Report to MHRA

Question 10

Where does uticaria and angiodema affect?

Answer 10

Tongue, lips, eyelids and genitalia

URT - can cause death

Unilateral or symmetrical

Question 11

What drugs cause uticaria/angiodema?

Answer 11

1. Ace inhibitors
2. Anaesthetics
3. Antibiotics
4. Dextrans
5. Enzymes
6. NSAID’s and opioids
7. Hydralazine
8. Radio-contrast media

Question 12

What is Steven Johnson syndrome?

Answer 12

Extensive erythema multiforme of face and trunk causing fever, malaise, myalgia and arthralgia

Stop - give fluids and systemic steroids

Question 13

What drugs cause Steven Johnson syndrome?

Answer 13

1. Allopurinol
2. Carbamazepine
3. Lamotrigine
4. Penicillins
5. Tetracyclines
6. Sulphonamides
7. NSAID’s

Question 14

What is a photosensitivity reaction?

Answer 14

Phototoxic - exaggerated sunburn, weeping and desquamation

Rash confined to area exposed to light

Question 15

What causes photosensitivity?

Answer 15

High doses of drug and sufficient light

Amiodarone

Question 16

How do you treat photosensitivity?

Answer 16

1. Use sunblock
2. Chlorpromazine