Scaly Rashes, Gabapentin overuse

Thanks Bruce for a great case! This is a patient with an extensive medication list who presented with a diffuse subacute progressive scaly and vesicular rash ultimately thought to be drug induced psoriasis from lisinopril.

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Main points:

  • 1) Lidocaine patches are a good first line for postherpetic neuralgia, especially in patients who could potentially not do well with the side effects of systemic gabapentinoid drugs.
  • 2) A 30g container of steroid generally covers the entire body surface area once. Therefore, think about how much you should prescribe when you want to start a topical steroid on a patient.
  • 3) In patients with a pruritic scaly rash that is otherwise well appearing, it is reasonable to trial a topical antifungal and if that does not work a topical steroid. If the topical steroid is started first and the rash is fungal, it could make the rash much worse.

Want to learn more?

Postherpetic neuralgia

Here is an excellent review article on postherpetic neuralgia, including a great table comparing topical and oral therapies. We discussed today that there has been a rise in sales of gabapentinoids in the era of the opioid epidemic and we should use these drugs judiciously and try to move away from a pharmacological approach to treating chronic pain.

Ddx scaly rash

Here are previous reports with differentials on morbiliform drug eruptions and papular drug rashes.

In addition to evaluating for infectious, autoimmune, malignant and drug causes, we discussed also thinking about common conditions with scaly rashes including psoriasis, fungal infection, lichen planus, tinea, syphilis, eczema, contact dermatitis and pityriasis rosea. Here is a great powerpoint and table from the American Academy of Dermatology comparing various common papulosquamous rashes.