Fixed drug eruption

What is a fixed medication? eruption?

A fixed drug rash is a allergic reaction to a medication that characteristically recurs at the same site or sites each time a particular medication is taken.

• The number of sites involved may increase over time.
• Usually only one medication is involved, although independent lesions from more than one medication have been described.
• Cross-sensitivity to related medications may occur, and there are occasional reports of same-site recurrences induced by medications that appear to be chemically unrelated.
• Sometimes the inducing drug can be re-administered without causing the symptoms to come back. patch(es), and there may be a refractory period during which no reaction can occur after the onset of the fixed drug eruption.

How does fixed drug rash occur?

It is unclear exactly how a fixed drug rash arises and why only certain areas of the skin are affected.

It is believed that a antigen of the active drug cytotoxic T cells at epidermis. These launch cytokines (inflammatory mediators), such as interferon-γ, granzyme B and perforin. Cytokines, with helper T cells and neutrophils, destroys local skin cells (keratinocytes and melanocytes) Cytotoxic T cells remain in the epidermis and release more cytokines when re-exposed to the causal drug.

What does fixed drug rash look like?

Fixed drug rash presents as well-defined round or oval patches of redness and swelling of the skin, sometimes surpassed by a blister. This then fades to a purple or brown color and the blister shrinks and peels off. In mucous membrane sites (lips, vulva, penis), extensive ulceration it can happen.

The hands and feet, lips, eyelids, genitals and perianal The areas are common sites.

Lesions usually develop between 30 minutes and 8 hours after taking the medication. At first, they are sometimes solitary, but with repeated attacks, new lesions may appear and existing lesions may increase in size.

As healing occurs, crust and climbing They are followed by a persistent dark brown color at the site. This may fade but often persists between attacks. Pigmentation It tends to be more extensive and pronounced in people with dark skin. Fixed drug pigmentation rashes fades when the offending drug is avoided.

Fixed non-pigmented rashes due to pseudoephedrine and piroxicam have been reported.

Local or general symptoms accompanying a fixed drug eruption are mild or absent.

Generalized bullous fixed drug rash

Sometimes a patient with fixed drug eruption may present with multiple sites simultaneously where there are bullas and erosions. These are often intertriginous sites. When it is extensive, the director differential diagnosis It's Stevens-Johnson. syndrome / / toxic epidermal necrolysis

Medications that cause a fixed drug rash

The number of drugs capable of causing fixed rashes is large. Most reactions are due to the following medications.

• Paracetamol/phenacetin and other pain relievers

• Tetracycline antibiotics; doxycycline, minocycline

• Sulfonamide antibiotics including trimethoprim + sulfamethoxazole, sulfasalazine
• Acetylsalicylic acid/aspirin

• Non-steroidal anti-inflammatory drugs (NSAID) including ibuprofen

• Sedatives including barbiturates, benzodiazepines and chlordiazepoxide
• Hyoscine butyl bromide
• Dapsone
• Phenolphthalein (an old-fashioned laxative for constipation)
• Quinine