What is the recommended course of action for a patient prescribed Tremfya (Guselkumab) 100mg/mL subcutaneous injection every eight weeks?

Recommended Management for Tremfya (Guselkumab) Prescribed Every 8 Weeks

Continue the prescribed regimen of Tremfya 100mg subcutaneous injection every 8 weeks as maintenance therapy, ensuring the patient completed the appropriate loading doses at week 0 and week 4. 1

Verify Correct Dosing Schedule

The prescription indicates maintenance dosing (every 8 weeks), which is appropriate only after proper induction:

• For moderate-to-severe plaque psoriasis: The standard FDA-approved regimen is 100mg subcutaneous injection at week 0, week 4, then every 8 weeks thereafter 1, 2
• For psoriatic arthritis: Guselkumab 100mg every 8 weeks is an established maintenance regimen following appropriate induction 1
• For ulcerative colitis: Different dosing applies - 200mg subcutaneous every 4 weeks or 100mg every 8 weeks after IV induction 3, 4
• For Crohn's disease: Multiple regimens exist depending on induction route (IV vs subcutaneous), with maintenance options of 100mg every 8 weeks or 200mg every 4 weeks 3, 5, 6

Critical verification needed: Confirm the patient received loading doses at week 0 and week 4 before transitioning to the every-8-week maintenance schedule. 1

Assess Treatment Response

Evaluate clinical response at 12 weeks from treatment initiation to determine if guselkumab is providing adequate disease control: 2

• For psoriasis, assess PASI score improvement (70-73% of patients achieve PASI 90 by week 16) 2
• For psoriatic arthritis, assess ACR response criteria and extra-articular manifestations 1
• For inflammatory bowel disease, assess clinical remission and endoscopic response 4, 5, 6

If partial response at 12 weeks (for psoriasis): Consider adding topical corticosteroids, vitamin D analogues, methotrexate, or ultraviolet B light therapy 2

Monitor for Adverse Events

Screen for infections at each visit, as respiratory tract infections are the most common adverse events (occurring in 38.3% of Crohn's disease patients and similar rates in other indications): 3

• Upper respiratory tract infections, nasopharyngitis, COVID-19, and influenza are most frequent 3, 7
• Serious infection rate is low (1.0 per 100 patient-years) 7
• No active tuberculosis was reported in psoriasis studies, though rare cases occurred in Crohn's disease trials in TB-endemic regions 3, 7

Monitor for hypersensitivity reactions, including anaphylaxis, though these are rare: 3

• Instruct patients to discontinue immediately and seek medical attention if symptoms develop 3
• Injection site reactions occur in 1.1-8.9% of patients depending on indication 3

Assess for hepatotoxicity if symptoms develop (unexplained rash, nausea, vomiting, abdominal pain, fatigue, anorexia, jaundice, or dark urine): 3

• ALT ≥5× ULN occurred in 0.3-1.7% of Crohn's disease patients without concurrent bilirubin elevation 3
• No routine liver enzyme monitoring is mandated, but investigate if clinical symptoms arise 3

Ensure Appropriate Infection Screening

Verify tuberculosis screening was completed before initiating guselkumab: 3

• PPD or interferon-gamma release assay should be negative or latent TB adequately treated
• Advise patients to report symptoms of TB (unexplained fever, cough, difficulty breathing) 3

Avoid live vaccines during guselkumab therapy: 3

• Update all non-live vaccines before starting treatment when possible
• Inactivated vaccines can be administered during therapy 3

Long-Term Safety Considerations

Reassure patients about favorable long-term safety profile based on integrated analysis of 4,399 patients followed for 10,787 patient-years: 7

• Serious adverse event rate: 5.4 per 100 patient-years 7
• Malignancy rate: 0.6 per 100 patient-years 7
• Major adverse cardiovascular events: 0.3 per 100 patient-years 7
• No cases of Crohn's disease or ulcerative colitis were reported in psoriasis/psoriatic arthritis studies 7

Monitor for drug interactions with CYP450 substrates, particularly CYP2D6 substrates with narrow therapeutic index: 3

• Guselkumab may alter CYP450 enzyme formation through cytokine modulation
• Consider therapeutic drug monitoring or dose adjustment for affected medications 3

Special Population Considerations

For patients with both psoriatic arthritis and significant skin involvement, IL-23 inhibitors like guselkumab are preferred over TNF inhibitors based on EULAR guidelines 2

Safety during pregnancy and lactation is unknown for IL-23 inhibitors: 1

• Antibodies are effectively secreted during lactation; exercise caution 1
• Discuss family planning and contraception with patients of childbearing potential 1

Pediatric use: Guselkumab is not FDA-approved for pediatric patients (etanercept and ustekinumab are the only biologics approved for pediatric psoriasis) 1