Common Psoriasis Drug Interactions

(LifeWire) - When it comes to battling the red, itchy scales of psoriasis, some treatments work better in tandem. But what drug interactions work against healing?

Fortunately, negative drug-to-drug or drug-to-nutrient interactions are relatively unusual. That's good news for the 750,000 Americans of all ages who cope with psoriasis, a chronic skin disease caused by a faulty immune system that allows skin cells to reproduce 10 times faster than normal. The result is crusty, silver-scaled patches, or plaques, that can occur on any part of the body.

Which psoriasis therapies are employed depends a great deal on the location of plaques and how extensively they cover the body. Although two-thirds of patients with psoriasis, known as "psoriatics," have mild or moderate forms of the disease. The rest endure patches on 20% or more of their skin surface. These severely affected patients are perhaps more prone to negative drug interactions because the types of medications they use are quite powerful and are sometimes injected or taken orally, extending their effects to the entire body.

The immunosuppressant cyclosporine, for example, which is also used in patients with organ transplants, has many potential drug interactions. Some prescription antibiotics, anticonvulsants, anti-inflammatory agents and calcium channel blockers interact negatively with cyclosporine, as well as aspirin, naproxen and ibuprofen, which are available over the counter (OTC). Naproxen and ibuprofen, which are classified as NSAIDs (non-steroidal anti-inflammatory drugs), are particularly toxic to the kidneys when paired with cyclosporine.

These and other combinations may affect how cyclosporine combats psoriasis, causing either too much or too little of the drug to be available in the bloodstream. Oral contraceptives, for example, strengthen in concentration when taken with cyclosporine, while effects of the mood-elevating herb St. John's Wort weaken.

Cyclosporine also has a well-documented interaction with grapefruit juice. Some chemicals in grapefruit juice, as well as the highly acidic juices made from tangelos and Seville oranges, interfere with the enzymes that digest medications for a variety of ailments (not just psoriasis), resulting in excessively high concentrations of the drug in the bloodstream.

Because cyclosporine lowers a patient's immunity, it should also be noted that anyone planning on receiving disease vaccinations -- including flu shots -- should first check with their doctors. Sometimes the psoriasis drug can be discontinued for a few weeks surrounding the time of the vaccination. Patients taking cyclosporine should also avoid people recently vaccinated with live viruses, including polio and the nasal-administered flu vaccine.

As noted earlier, psoriatics -- particularly those with mild or moderate cases -- are often prescribed medications, many of them topical, which prove beneficial in tandem. Corticosteroid creams, for example, can be used sequentially with creams made from vitamin D derivatives to optimize the results of both. Salicylic acid, however -- an ingredient in many scale-reducing creams, ointments and shampoos -- will inactivate vitamin D creams. And when natural sunlight or ultraviolet lamps are prescribed to combat psoriasis (by slowing skin cell growth), patients need to take care. Several psoriasis drugs -- as well as medicines for other conditions -- increase light sensitivity and can result in sunburns.

Care should be taken using sun lamps and the following drugs: coal or pine tar products, most of which are OTC; prescription vitamin A derivatives, such as tazarotene (Tazorac); and some antibiotics and high blood pressure medications. Check with your doctor to learn which of your prescriptions increase photosensitivity.

Since it's impossible to cover all potential medication interactions and risks, especially those associated with cyclosporine, patients with further questions should consult their doctor.

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