Generic Name

Avonex

Mechanism

Avonex modulates immune function via:
• Inhibition of pro‑inflammatory cytokines (IL‑1, TNF‑α, IFN‑γ) and enhancement of anti‑inflammatory cytokines (IL‑10).
• ↓ T‑cell migration across the blood–brain barrier by down‑regulating adhesion molecules (ICAM‑1, VCAM‑1).
• Promotion of T‑cell apoptosis and induction of an anti‑viral state, reducing oligodendrocyte injury and demyelination.

*Key point:* The drug’s action is immune‑regulatory rather than neuroprotective.

Pharmacokinetics

• Absorption: Subcutaneous, peak plasma ~3–12 hours post‑dose.
• Distribution: Limited penetration into CNS; systemic effect is primary.
• Metabolism: Proteolytic degradation to amino acids; no significant hepatic metabolism.
• Elimination: Renal clearance of metabolites; half‑life 3–4 hours.
• Drug interactions: None significant; avoid concomitant high‐dose steroids.

Indications

• Relapsing‑remitting multiple sclerosis (RRMS) – first‑line therapy for patients with:
• ≥2 relapses or ≥1 severe relapse in the past 12 months.
• MRI evidence of new lesions.
• Pre‑emptive therapy in clinically isolated syndrome (CIS) with MRI lesions.

Contraindications

• Contraindications:
• History of severe allergic reaction to interferons.
• Active uncontrolled infections (e.g., hepatitis, severe bacterial infection).
• Untreated lymphoma or autoimmune disease requiring immunosuppressants.
• Warnings:
• Hepatotoxicity: monitor ALT/AST; discontinue if ≥5× ULN.
• Myocarditis in patients with pre‑existing heart disease.
• Lymphopenia risks with overlapping immunosuppressants.
• Potential pregnancy concerns – advise contraception.

Dosing

• Standard dose: 30 µg (1 mL) injected subcutaneously once weekly.
• Injection technique:

1. Rotate injection sites (abdomen, thigh, upper arm).

2. Clean with alcohol; do *not* remove skin after insertion.

3. Reconstitute with 0.5 mL of preservative‑free water before each dose if necessary.
• Rescue: For breakthrough relapse, high‑dose steroid therapy is still needed; interferon‑β does not replace steroids.

Adverse Effects

*Management:* Pre‑emptive low‑dose acetaminophen reduces flu‑like symptoms; consider temporary dose reduction if symptoms persist.

Monitoring

• Baseline: CBC, AST/ALT, urinalysis, hepatitis B/C, HIV screening.
• Every 3 months: CBC, LFTs, renal function.
• Annual: MRI to evaluate new lesions; immunologic screening if immunosuppressants used concurrently.
• Pregnancy: Early prenatal screening if conception is anticipated; interferon‑β is category B.

Clinical Pearls

• Use a rotating injection site chart to minimize lipodystrophy; patients often forget to rotate.
• Flu‑like symptoms are dose‑dependent—a 30 µg dose reduces incidence vs 22 µg but still high enough for tolerance.
• Consider co‑administration with glatiramer acetate in patients needing dual coverage after relapse; careful monitoring for hematologic toxicity.
• Adherence tracking with smartphone reminders improves monthly injection consistency >90 %.
• Switching to recombinant interferon‑β‑1b (Betaseron) may be warranted for patients intolerant to allergic injection‑site reactions but maintain the same therapeutic goal.
• Pregnancy counseling: While data are reassuring, no definitive long‑term safety data exist; advise patients to weigh benefits vs obstetric risks.

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• *Clinical references:* Kappos et al., *Neurology* 2008; O'Connor et al., *Lancet Neurology* 2014.