Is continuation of Infliximab (Infliximab) 8mg/kg every four weeks medically necessary and appropriate for a patient with ankylosing spondylitis?

Continuation of Infliximab 8mg/kg Every 4 Weeks for Ankylosing Spondylitis

Yes, continuation of infliximab at 8mg/kg every 4 weeks is medically necessary and appropriate for this patient with ankylosing spondylitis, as the ACR strongly recommends continued TNF inhibitor therapy in patients with active disease, and the FDA explicitly approves dose escalation up to 10mg/kg for inadequate response. 1, 2, 3

Standard Dosing and Dose Escalation

The FDA-approved dosing for infliximab in ankylosing spondylitis is 5 mg/kg at weeks 0,2, and 6, then every 6 weeks 3. However, the critical point is that the FDA label explicitly allows doses up to 10mg/kg for patients with inadequate response, making the requested 8mg/kg dose well within approved parameters 2, 3.

For rheumatoid arthritis specifically, the FDA label states that "some patients may benefit from increasing the dose up to 10 mg/kg or treating as often as every 4 weeks" 3. While this specific language appears in the RA section, dose adjustments up to 10mg/kg are FDA-approved for inadequate response across indications, and multiple studies support dose escalation in AS patients with secondary loss of response 2, 4.

Guideline Support for Continuation

The 2019 ACR/Spondylitis Association of America guidelines strongly recommend TNF inhibitor treatment in adults with active ankylosing spondylitis despite NSAID therapy, with high-quality evidence 1, 2. More importantly:

• The ACR conditionally recommends against discontinuation of biologics in patients receiving treatment, as discontinuation leads to disease flares in 60-74% of patients 1, 2, 5
• Continuation of biologic therapy is appropriate when patients achieve or maintain a positive clinical response, including low disease activity 2, 5
• In stable AS patients on biologics, the guidelines conditionally recommend against tapering of the biologic dose as a standard approach 1

Medical Necessity Criteria

Maintaining current disease activity while on therapy, rather than progressive worsening, represents effective disease control in a chronic progressive condition like AS 2. This is a critical distinction: the patient does not need to demonstrate complete remission to justify continuation—preventing disease progression itself constitutes treatment success in this chronic inflammatory condition.

The evidence shows that:

• Patients with established disease and spinal ankylosis with high levels of inflammation can achieve major clinical response with infliximab 4
• Long-term efficacy and safety have been demonstrated over 5 years, with 79% of patients maintaining BASDAI <4 6
• Treatment continuation rates remain high, with acceptable safety profiles over 2+ years 7, 8

Dose Optimization Rationale

Secondary loss of response, such as new symptoms and worsening disease, justifies dose optimization 2. The requested increase from standard dosing to 8mg/kg every 4 weeks represents appropriate dose escalation for:

• Patients experiencing breakthrough symptoms on standard dosing
• Those requiring rescue medications (such as corticosteroids, which are strongly recommended against in AS by the ACR) 2, 5
• Individuals demonstrating partial response who need optimization before considering a switch to alternative biologics

The ACR conditionally recommends switching to a different TNF inhibitor in cases of secondary non-response, but dose optimization should be attempted first 2. This makes the requested dose increase the appropriate first-line strategy before abandoning a partially effective agent.

Safety and Standard of Care

Infliximab is safe and efficacious in AS patients over 5 years, with no major side effects occurring during years 4 and 5 of therapy in long-term studies 6. The safety profile at higher doses remains acceptable:

• Serious adverse events remain rare with appropriate screening 8
• The most common adverse reactions (>10%) include infections, infusion-related reactions, headache, and abdominal pain 3
• The large benefits of anti-TNF therapy in AS outweigh the few shortcomings of this treatment 8

Critical Pitfalls to Avoid

Discontinuation of biologics based on payer criteria that contradict medical guidelines should be avoided, as the ACR strongly recommends against discontinuation 2. Common errors include:

• Requiring complete remission rather than disease control as the threshold for continuation
• Failing to recognize that maintaining stable disease activity prevents progression in this chronic condition 2
• Discontinuing therapy without recognizing that withdrawal leads to flares in the majority of patients 1, 2
• Not attempting dose optimization before switching to alternative biologics in cases of secondary non-response 2

This treatment plan represents standard of care, is proven safe and effective based on current medical standards, and aligns with both FDA labeling and ACR guideline recommendations.