40.3 Psoriatic Drugs

Psoriatic Drugs

Psoriasis is a chronic autoimmune condition where skin cells multiply far too quickly, building up into thick, inflamed plaques. Psoriatic drugs work by either slowing that abnormal cell turnover, suppressing the overactive immune response driving it, or both. Treatment follows a stepwise approach: topical therapies for mild disease, systemic agents for moderate-to-severe cases, and biologics when other options fail or aren't tolerated.

Nurses need a solid grasp of these medications because many carry significant risks, from liver toxicity to serious infections. Patient education and ongoing monitoring are central to safe, effective therapy.

Key Features and Mechanisms of Action

Topical Treatments

Topical agents are first-line for mild-to-moderate psoriasis. They're applied directly to plaques and generally carry fewer systemic risks than oral or injectable drugs.

• Corticosteroids suppress the local immune response and reduce production of inflammatory cytokines. This decreases inflammation and slows the rapid skin cell turnover that forms plaques. They range from low-potency (hydrocortisone) to high-potency (clobetasol), and potency selection depends on the body site and severity.
• Vitamin D analogs (calcipotriene) bind to vitamin D receptors on skin cells, slowing their proliferation and promoting normal differentiation. Often paired with a corticosteroid for better results.
• Retinoids (tazarotene) bind to retinoic acid receptors and regulate gene transcription, which normalizes skin cell growth and reduces inflammation. Can be quite irritating to surrounding skin.
• Calcineurin inhibitors (tacrolimus, pimecrolimus) block calcineurin, an enzyme needed for T-cell activation. These are particularly useful on sensitive areas like the face and skin folds, where long-term corticosteroid use is risky.

Systemic Treatments

Systemic agents are reserved for moderate-to-severe psoriasis or cases that don't respond to topicals. They work throughout the body, so the side effect profile is more significant.

• Methotrexate blocks dihydrofolate reductase, an enzyme essential for DNA synthesis. This slows the rapid division of skin cells and suppresses the inflammatory immune response. It's typically dosed once weekly (not daily, which is a common and dangerous dosing error).
• Cyclosporine inhibits calcineurin in T-cells, preventing production of inflammatory cytokines. It works quickly but is usually limited to short-term use because of nephrotoxicity risk.
• Acitretin is an oral retinoid that binds retinoic acid receptors, normalizing skin cell differentiation. It's the only systemic psoriasis drug that is not immunosuppressive, which matters for patients at high infection risk.
• Apremilast inhibits phosphodiesterase-4 (PDE4), which raises intracellular cyclic AMP levels. Higher cAMP suppresses production of inflammatory mediators like TNF-α and IL-17. It has a milder side effect profile than other systemics.

Biologic Treatments

Biologics are protein-based drugs that target specific parts of the immune cascade driving psoriasis. They're used for moderate-to-severe disease and are given by injection or infusion.

• TNF-α inhibitors (etanercept, adalimumab, infliximab) neutralize tumor necrosis factor-alpha, a major pro-inflammatory cytokine in psoriasis.
• IL-12/23 inhibitors (ustekinumab) block interleukin-12 and interleukin-23, preventing the activation and differentiation of T-cells that drive psoriatic inflammation. Dosed less frequently than TNF-α inhibitors (every 12 weeks after loading doses).
• IL-17 inhibitors (secukinumab, ixekizumab) block interleukin-17, a cytokine that plays a central role in forming psoriatic plaques. These tend to produce rapid, significant skin clearance.

Side Effects, Drug Interactions, and Contraindications

Topical Treatments

• Side effects: Skin irritation is common across all topicals. Long-term corticosteroid use can cause skin atrophy (thinning), striae, and telangiectasias. Higher potency and longer duration increase this risk.
• Drug interactions: Minimal for topicals due to limited systemic absorption.
• Contraindications: Hypersensitivity to active ingredients. Avoid potent corticosteroids on thin-skinned areas (face, groin) for extended periods.

Systemic Treatments

Methotrexate

• Side effects: Hepatotoxicity, bone marrow suppression (monitor CBC), and GI upset (nausea, vomiting, diarrhea). Folic acid supplementation is routinely prescribed to reduce these effects.
• Drug interactions: NSAIDs, trimethoprim, and probenecid decrease methotrexate clearance, raising toxicity risk.
• Contraindications: Pregnancy (Category X, teratogenic), liver disease, immunodeficiency, significant renal impairment.

Cyclosporine

• Side effects: Nephrotoxicity (dose-dependent), hypertension, and increased infection risk.
• Drug interactions: Statins, calcium channel blockers, and digoxin levels can increase. Grapefruit juice also raises cyclosporine levels.
• Contraindications: Uncontrolled hypertension, renal insufficiency.

Acitretin

• Side effects: Highly teratogenic, dry skin and mucous membranes, elevated liver enzymes, hyperlipidemia.
• Drug interactions: Tetracyclines (risk of pseudotumor cerebri), methotrexate (additive hepatotoxicity), and alcohol. Alcohol converts acitretin to etretinate, which has a half-life of 120 days and extends the teratogenic risk.
• Contraindications: Pregnancy. Women must avoid pregnancy for at least 3 years after stopping acitretin. Severe liver or kidney disease.

Apremilast

• Side effects: Diarrhea and nausea (often improve after the first few weeks), upper respiratory infections, weight loss. Screen for depression, as psychiatric adverse effects have been reported.
• Drug interactions: Strong CYP3A4 inducers (e.g., rifampin) decrease apremilast effectiveness.
• Contraindications: Hypersensitivity to apremilast.

Biologic Treatments

• Side effects: Increased infection risk (including reactivation of latent tuberculosis), injection site reactions (redness, swelling, pain at the injection site).
• Drug interactions: Avoid live vaccines during biologic therapy. Use caution when combining with other immunosuppressants due to additive infection risk.
• Contraindications: Active infections (must be resolved before starting therapy), history of malignancy. TNF-α inhibitors are specifically contraindicated in moderate-to-severe heart failure (NYHA Class III/IV).

Essential Nursing Considerations

1. Assess baseline knowledge. Determine the patient's understanding of their medication, correct dosage, and proper administration technique before starting therapy.
2. Obtain baseline labs. For systemic and biologic agents, ensure labs are drawn as ordered: liver function tests and CBC for methotrexate, renal function and blood pressure for cyclosporine, TB screening for biologics.
3. Monitor for adverse effects. Track labs at prescribed intervals and assess for clinical signs of toxicity (jaundice, unusual bruising/bleeding, signs of infection).
4. Use proper technique for injectables. Administer biologics via subcutaneous injection or IV infusion as prescribed. Maintain sterile technique and rotate injection sites to minimize reactions.
5. Watch for infection. Patients on immunosuppressive therapies are vulnerable. Monitor for fever, chills, cough, or localized signs of infection and report promptly.
6. Verify methotrexate dosing. Confirm the dose is prescribed once weekly, not daily. Daily dosing is a well-documented, potentially fatal medication error.
7. Document treatment response. Assess and record changes in plaque severity, skin clearance, and patient-reported symptoms at each visit.
8. Support adherence. Discuss barriers to consistent use (cost, complexity, side effects) and problem-solve with the patient and care team.

Patient Education Plan

• Explain the medication clearly. Cover the drug's purpose, how it works, and realistic expectations for results. Many psoriasis treatments take weeks to show improvement, so setting expectations early prevents discouragement.
• Demonstrate topical application. Show patients how to apply creams or ointments to affected areas only, using the correct amount. Provide written instructions they can reference at home.
• Teach self-injection technique for patients on biologics. Use a hands-on approach with demonstration devices, allow return demonstration, and confirm comfort before the patient does it independently.
• Review side effects and red flags. Teach patients to recognize and report signs of infection (fever, chills, redness, swelling), unusual bruising or bleeding, and persistent GI symptoms. Provide specific guidance on what warrants a call to the provider versus an ER visit.
• Address reproductive safety. For teratogenic drugs (methotrexate, acitretin), confirm effective contraception is in place and that the patient understands the required timeframe to avoid pregnancy after discontinuation.
• Discuss lifestyle strategies. Recommend regular moisturizer use to manage dryness, stress reduction techniques, and avoidance of known triggers (skin trauma, certain medications, heavy alcohol use).
• Provide support resources. Direct patients to the National Psoriasis Foundation and local support groups. Chronic skin conditions carry a significant psychosocial burden, and peer support can improve outcomes.
• Reinforce follow-up. Emphasize the importance of regular appointments and lab monitoring, especially for systemic and biologic therapies. Help patients understand that these visits are about catching problems early, not just checking a box.