Generic Name

Xiaflex

Mechanism

• Collagenase activity: selectively digests type I and III collagen, the main structural components of Dupuytren’s cords.
• Facilitation of rupture: Local injection of Xiaflex causes enzymatic fragmentation, allowing rapid, controlled de‑hanging of the cord under joint manipulation.
• Minimal systemic effect: The drug is confined to the injection site; systemic absorption is negligible, limiting systemic toxicity.

Pharmacokinetics

• Route: Intralesional injection into palpable cords or trigger finger nodules.
• Absorption: Predominantly local; serum levels are <1 ng/mL, below the therapeutic window for systemic action.
• Metabolism: Proteolytic degradation by local tissue proteases; no hepatic metabolism or renal excretion.
• Half‑life: Approx. 4–6 h in the local tissue; rapid clearance from systemic circulation.
• Drug interactions: None known due to lack of systemic exposure.

Indications

• Primary Dupuytren’s contracture: Palpable cords causing flexion contracture of the finger, especially the proximal interphalangeal (PIP) joint.
• Trigger finger: Nodular or fibrotic thumb or finger flexor tendon pathology causing locking or pain.
• Contraindicated: Adjacent tendon or joint disease, severe vascular compromise, or systemic musculoskeletal disorders that would preclude improvement of finger function.

Contraindications

• Absolute contraindications
• Hypersensitivity to *Clostridium histolyticum* or any excipient.
• Active infection at the injection site.
• Severe peripheral vascular disease or edema affecting finger perfusion.
• Precautions
• Coagulopathies: Fluids may provoke bleeding; avoid in patients with uncontrolled bleeding diatheses, recent anticoagulant therapy, or platelet disorders.
• Pregnancy/Lactation: Use only if benefits outweigh potential risks; data is limited.
• Recent surgery or trauma: Delay until wound healing complete.

Dosing

• Concentration: 0.58 mg/mL (0.05 mL/2 mg vial).
• Injection procedure

1. Preparation: Skin cleansed, local anesthesia optional.

2. Administration: 0.05 mL (0.58 mg) injected into the mid‑cord of the PIP joint.

3. Post‑dose manipulation: Within 30–60 min, gentle extension (malleable holding) to guarantee cord rupture.
• Schedule
• Maximum of 2 injections per finger per session.
• Up to 4 sessions, spaced 4–6 weeks apart, may be repeated up to 7–21 injections total under follow‑up.
• Dosage escalation: Escalate only in patients with residual contracture >20° after prior sessions.

Adverse Effects

Monitoring

• Range of motion: Baseline and post‑injection improvement at 1–2 weeks.
• Vascular status: Check capillary refill, color, temperature pre‑ and post‑injection.
• Coagulopathy labs (if indicated): PT/INR, aPTT in patients on anticoagulation.
• Patient diary: Document pain score, function, and any adverse signs.
• Follow‑up visits: 1 month, 3 months, and post‑treatment quality‑of‑life assessment.

Clinical Pearls

• Technique matters: Use a 1 mm needle, avoid intramuscular injection; aim for the deepest portion of the cord.
• “Skin‑tendinous zone”: Inject just proximal to the tendon sheath to reduce tendinous damage.
• Bleeding risk monitoring: For patients on warfarin or DOACs, evaluate INR/PTRN and consider dose adjustment or temporary cessation 48 h before injection.
• Pain control: Use topical lidocaine‑based preparations pre‑injection, but avoid systemic opioids; NSAIDs suffice in most cases.
• Re‑treatment threshold: Consider a new session if contracture exceeds 30° after 4 weeks or if functional gains plateau at <25 ° improvement.
• Patient education: Instruct patients to keep fingers extended for 24 h post‑injection to promote optimal cord rupture and reduce pain spikes.
• Adjunct therapy: Post‑injection splinting (e.g., night splint) can maintain gains and mitigate return of contracture.

*Xiaflex* remains a first‑line, minimally invasive option for Dupuytren’s contracture and trigger finger, offering high functional success when administered with meticulous technique and appropriate patient selection.