Sinemet Shortage: What Providers and Prescribers Need to Know in 2026

The ongoing shortage of carbidopa/levodopa extended-release (ER) formulations continues to create clinical challenges for patients with Parkinson's disease (PD) in 2026. This article provides a concise overview of the current supply landscape, formulation-specific guidance, conversion strategies, and actionable steps to support patient access.

Current Shortage Landscape (2026)

Intermittent shortages of carbidopa/levodopa have been reported to the ASHP and FDA since the early 2010s. The situation intensified following several key manufacturer exits:

Merck discontinued brand-name Sinemet CR 50/200 mg tablets around November 2019 and the 25/100 mg CR tablets around February 2020.

Accord Healthcare discontinued carbidopa/levodopa 25/100 mg ER tablets. Only the 50/200 mg ER strength remains available from Accord.

Sun Pharma discontinued carbidopa/levodopa ODT 25/250 mg tablets (NDC 47335-0188-88) in December 2022. Viatris/Mylan discontinued ODT formulations in 2021.

Immediate-release tablets remain available from multiple generic manufacturers (Teva, Amneal, Sun, and others), though localized shortages persist.

Brand products—Rytary (extended-release capsules), Crexont (ER capsules, approved 2024), and Duopa (enteral suspension)—are not in shortage but present cost and access barriers due to price and prior authorization requirements.

2026 FDA Safety Update: Vitamin B6 Deficiency

On March 20, 2026, the FDA issued a MedWatch safety communication and required labeling updates for all carbidopa/levodopa products. The new warnings address the risk of vitamin B6 (pyridoxine) deficiency during long-term therapy, which can lead to seizures, peripheral neuropathy, depression, and confusion. Prescribers should evaluate vitamin B6 levels prior to initiating therapy, periodically during treatment, and as clinically indicated. Supplementation may be warranted in deficient patients.

The 'Eight Tablet Limit': Clinical Implications

The original FDA labeling language for Sinemet lists a maximum of eight tablets per day. Pharmacy dispensing software and insurance utilization management systems frequently flag—or auto-reject—prescriptions exceeding this limit. This is not a clinical ceiling. Many patients with advanced PD require higher daily doses, and the eight-tablet language was descriptive of clinical trial dosing rather than prescriptive.

Strategies for overcoming the eight-tablet limit:

Submit a prior authorization with clinical documentation of disease severity and prior treatment history

Consider prescribing 25/250 mg tablets (fewer tablets per equivalent levodopa dose)

Add a COMT inhibitor (e.g., entacapone/Comtan) to extend the duration of each levodopa dose, reducing total tablet count

Formulation Conversion: ER to IR

For patients currently on ER tablets who cannot obtain their usual formulation, conversion to immediate-release tablets is the most common approach. Key pharmacokinetic considerations:

ER tablets have approximately 70–75% bioavailability relative to IR formulations

When converting, total daily levodopa dose should generally be increased by approximately 25–30%

IR tablets require more frequent dosing (every 3–4 hours vs. every 6–8 hours for ER)

Counsel patients to expect a transition period with potential motor fluctuations until the optimal IR schedule is established

Available Brand ER Alternatives

Rytary: Extended-release capsules. Multi-bead technology. Available in four strengths (23.75/95 mg, 36.25/145 mg, 48.75/195 mg, 61.25/245 mg). Conversion from IR or CR is not 1:1; follow manufacturer dosing tables. Typically requires prior authorization. Dosing frequency: 3–5x daily.

Crexont: Approved 2024. Offers immediate and sustained-release profiles. Allows twice-daily dosing for many patients. May be an option if ER tablets remain unavailable and prior auth is achievable.

Stalevo (carbidopa/levodopa/entacapone): Combination product with a COMT inhibitor. May be available when standard carbidopa/levodopa is not. Particularly useful when trying to extend duration of effect.

Adjunctive Strategies to Maximize Available Doses

When carbidopa/levodopa supply is limited, adjunctive medications can help maximize the efficacy of available doses:

Entacapone (Comtan): COMT inhibitor that extends levodopa half-life by ~30–60 minutes. 200 mg taken with each carbidopa/levodopa dose.

Rasagiline or Safinamide: MAO-B inhibitors that reduce dopamine degradation. Useful adjuncts in patients experiencing 'off' periods.

Dopamine agonists (Pramipexole, Ropinirole): Can supplement or partially replace levodopa therapy. Use with caution in older patients given the increased risk of somnolence, impulse control disorders, and hallucinations.

Helping Patients Find Medications in Stock

Provider awareness of real-time pharmacy inventory directly improves patient outcomes. Referring patients to medfinder for providers allows you to streamline the process of locating in-stock medications for your patients. For a patient-facing overview of the shortage, see our Sinemet shortage update for 2026.