Avonex (Interferon Beta-1a) — Medicare Part D spending
Biogen-Idec · Rank #309 by total Part D spend · CMS data year 2023
Medicare Part D spent $139,326,335 on Avonex (Interferon Beta-1a) in 2023, the #309 drug by total Part D spending out of 3,598 drugs. That worked out to about $8,211.49 per dosage unit, $8,946 per claim and $78,010 per beneficiary, across 15,575 claims for 1,786 beneficiaries. Average spending per dosage unit rose +7.4% from 2022. These are aggregate Medicare program figures (gross drug cost), not the price you pay.
Source: CMS Medicare Part D Spending by Drug (data year 2023). Data as of June 2026.
Avonex (Interferon Beta-1a) spending at a glance (2023)
| Metric | Avonex (Interferon Beta-1a) |
|---|---|
| Total Part D spending (2023) | $139,326,335 |
| Total spending (2022) | $161,915,780 |
| Year-over-year change in total spending | -14.0% |
| Average spending per dosage unit (2023) | $8,211.49 |
| Change in spend per dosage unit (YoY) | +7.4% |
| Avg annual change per dosage unit (2019-2023 CAGR) | +3.7% |
| Average spending per claim (2023) | $8,946 |
| Average spending per beneficiary (2023) | $78,010 |
| Total claims (2023) | 15,575 |
| Beneficiaries (2023) | 1,786 |
| Total dosage units (2023) | 16,967 |
| Manufacturer(s) | Biogen-Idec |
| National rank by total spend (of 3,598 drugs) | #309 |
Source: CMS Medicare Part D Spending by Drug (data year 2023). Data as of June 2026.
2022 vs 2023
| Metric | 2022 | 2023 | Change |
|---|---|---|---|
| Total spending | $161,915,780 | $139,326,335 | -14.0% |
| Avg spend per dosage unit | $7,646.64 | $8,211.49 | +7.4% |
| Avg spend per claim | $8,523 | $8,946 | — |
| Avg spend per beneficiary | $73,398 | $78,010 | — |
| Total claims | 18,998 | 15,575 | — |
| Beneficiaries | 2,206 | 1,786 | — |
How Avonex compares with nearby drugs
Drugs with total Part D spending closest to Avonex (Interferon Beta-1a):
| Drug (rank) | Total spend 2023 | Per dosage unit | Per-unit YoY |
|---|---|---|---|
| Avonex (Interferon Beta-1a) (this drug, #309) | $139,326,335 | $8,211.49 | +7.4% |
| Metoprolol Tartrate* (Metoprolol Tartrate) (#307) | $140,066,633 | $0.0749 | +5.4% |
| Budesonide-Formoterol Fumarate (Budesonide/Formoterol Fumarate) (#308) | $140,028,972 | $25.57 | -7.2% |
| Vyvanse (Lisdexamfetamine Dimesylate) (#310) | $138,990,768 | $13.04 | +5.8% |
| Piqray (Alpelisib) (#311) | $138,440,781 | $461.12 | +6.1% |
| Qulipta (Atogepant) (#312) | $137,880,798 | $36.83 | +6.0% |
Frequently asked questions
How much does Medicare Part D spend on Avonex?
Medicare Part D spent $139,326,335 on Avonex (Interferon Beta-1a) in 2023 (the latest CMS data year), across 15,575 claims for 1,786 beneficiaries. That ranks #309 of 3,598 drugs by total Part D spending. This is gross drug cost (Medicare, plan and beneficiary payments combined), not the price you personally pay.
What is the average spending per dosage unit for Avonex?
In 2023, the weighted average Medicare Part D spending per dosage unit for Avonex (Interferon Beta-1a) was $8,211.49. Compared with 2022 it rose +7.4%. A "dosage unit" is one pill, tablet, milliliter or other billing unit, so this is not the price of a prescription.
Who makes Avonex?
CMS attributes Avonex (Interferon Beta-1a) to Biogen-Idec in the 2023 Part D spending file. Average spending per claim was $8,946 and per beneficiary $78,010.
Is the Avonex figure the price I pay?
No. These are aggregate Medicare Part D program figures (total gross drug cost and averages across all claims), published by CMS for transparency. Your out-of-pocket cost depends on your plan, formulary, deductible and coverage phase. Always check your plan and talk to your pharmacist or doctor.
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Source & what this means
Figures are from the CMS Medicare Part D Spending by Drug dataset (data year 2023, US public domain). "Total spending" is the gross drug cost — Medicare, plan and beneficiary payments combined — for Part D claims; it is not a list price, a negotiated price, or what any individual pays. Spending per dosage unit is volume-weighted across formulations. This is general public-spending information, not medical or pricing advice. Your own cost depends on your plan, deductible and coverage phase — verify with your Part D plan and a pharmacist. Data as of June 2026. See our methodology and disclaimer.
Last updated: 2026-06-20