Updated: Jun 28, 2020
When people think of the colour “red”, bad things come to mind, possibly due to an association with blood. For example, blood in stool or urine may be a red flag for referral. Red colour may be a sign of inflammation or infection as well, such as in diaper dermatitis and cellulitis.
As pharmacists, we are trained to look for drug-induced causes as part of their patient workup. Here, we are going to highlight the most common drug-induced causes which feature the colour red or orange.
1) Phenazopyridine: A dye used as an analgesic for urinary tract infection related symptoms such as burning, itching and pain. This medication can cause a red-orange discolouration of urine, which is harmless, but may cause a great deal of concern in patients who may mistaken it for blood if not notified in advance.
2) Rifampin and Isoniazid: Used for many infections, including tuberculosis or resistant infections. These medications cause a red-orange colour in everything: tears, sweat and urine.
3) Doxorubicin: Known as the “Red Devil”, it is used as anticancer therapeutic. Based on its nickname, it literally is a red liquid which appears in the urine as a red colour.
1) Topical medications: Minor irritations are always possible when using topical creams and monographs often mention redness or rash as adverse effects. Particularly with acne medications, the acne may get worse before it gets better. Example: Topical retinoids
2) Fluorouracil: Many chemotherapeutic agents can cause non-specific damage to skin; for example, topical and oral formulations of fluorouracil cause skin inflammation. For topical fluorouracil, make sure to counsel for redness, sores, crusts and peeling. Patients mistaken this for an allergic reaction. This is normal and expected in the treatment course of skin conditions such as actinic keratoses. It will get significantly worse before it gets better!
3) Blood thinners: Due to their mechanism of action, patients may expect to see unusual bruising, which may be a concern. Example: Warfarin
Are there any drug-induced red colours that you can think of? Feel free to comment and share!