NPI registry status
Active
2026 NPPES data Registered Nurse First Assistant NPI 1538493614 APRN, FNP
Verify on CMS → Maria Kostantacos, APRN, FNP
Registered Nurse First Assistant in Janesville, Wisconsin.
This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 2,649 in Registered Nurse First Assistant, and covers specialty classification, practice address, and Medicare Part D prescribing data when reported. According to CMS, every field reflects the provider's official federal registration, see our methodology.
Federal data, no proprietary rating.
We show these CMS records as-is - no composite score, no star rating, no editorial opinion layered on top.
Prescribing volume
84
Medicare Part D claims · 56 beneficiaries · Registered Nurse First Assistant avg: 419
Compiled from official public sources by the PlainDoctor editorial team.
What the federal data shows
Maria Kostantacos, APRN, FNP filed 84 Medicare Part D claims in 2023 as a Registered Nurse First Assistant in Janesville, Wisconsin.
- 84
- Part D claims, 2023
Every figure on this page comes straight from federal CMS records (NPPES, Medicare Part D, MIPS, Open Payments) - no proprietary rating or editorial opinion is applied.
Maria Kostantacos, APRN, FNP's Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2023, across all CMS prescribers nationally
84 0th percentile higher than 0% of 1,370,886 prescribers
Each bar is a band; taller bars hold more prescribers. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source CMS Medicare Part D Prescriber Public Use File · 2023
What does the federal data show about Maria Kostantacos, APRN, FNP?
Quality data not reportedPrimary specialty
Registered Nurse First Assistant
Medicare Part D claims
84 80% vs specialty avg
Specialty distribution in Wisconsin
How Registered Nurse First Assistant compares to other specialties among Wisconsin providers
Board certification
Not published by CMS
CMS does not publish a per-provider board-certification field in NPPES. PlainDoctor does not have a reliable per-specialty certification rate to show for Registered Nurse First Assistant. Verify directly:
How MIPS and board certification work
The Merit-based Incentive Payment System (MIPS) scores providers 0–100 across four performance categories: Quality, Cost, Promoting Interoperability, and Improvement Activities, weighted under 42 CFR §414.1380. Reporting is voluntary for many small practices, so absence of a MIPS score is not a quality signal.
Board certification through an ABMS or AOA member board signals voluntary post-licensure examination plus continuous Maintenance of Certification cycles. Verify any individual provider's status through certificationmatters.org (ABMS) or osteopathic.org (AOA).
Maria Kostantacos, APRN, FNP appears in the CMS NPPES registry as a Registered Nurse First Assistant provider holding APRN, FNP credentials at 1010 N WASHINGTON ST, Janesville, WI, 53548, with a listed phone of (608) 741-3800. NPI 1538493614 was issued on 09/23/2009.
Medicare Part D records for calendar year 2023 show 84 prescription claims written by this provider, covering 56 Medicare beneficiaries and totaling roughly $854 in drug spend, with an opioid prescribing rate of 41.7%.
Registered Nurse First Assistant is a narrow specialty nationwide, with 2,649 enrolled providers across 50 states and an average of 419 Part D claims per prescriber, so the context for interpreting these metrics differs meaningfully from a primary-care baseline.
Important: PlainDoctor is a directory of publicly available government data, not medical advice, a malpractice database, or a quality rating. Inclusion here does not imply a recommendation, and absence of complaints or sanctions on this page does not mean none exist, always verify credentials through the NPPES NPI Registry, your state medical board, and the ABMS or AOA before making healthcare decisions.
Practice Address
Provider Details
| NPI | 1538493614 |
|---|---|
| Specialty | Registered Nurse First Assistant |
| Credentials | APRN, FNP |
| Gender | Female |
| NPI Issued | 09/23/2009 |
Hospital and facility affiliations
Facilities where Maria Kostantacos, APRN, FNP bills Medicare from. Star ratings (1-5) are CMS Hospital Compare's "Hospital overall rating" - a composite of mortality, readmission, patient experience, safety, timely care, and efficient use of medical imaging measures. Source: CMS Care Compare.
Mercy Health System Corporation
Harvard, IL
Affiliations sourced from CMS Doctors and Clinicians National Downloadable File; hospital ratings from CMS Hospital General Information dataset (cross-referenced by facility name + state).
Medicare Part D Prescribing Data
CMS Medicare Part D prescriber-level data for calendar year 2023.
84
Total Claims
$854
Total Drug Cost
56
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 84
- Total Day Supply
- 859
- Generic Drug Cost
- $852
- Opioid Claims
- 35 (41.7% rate)
- Antibiotic Claims
- 19
Patient Demographics
- Average Patient Age
- 67.8 years
- Avg HCC Risk Score
- 1.60
- Gender Split
- 50% female / 50% male
- Age Distribution
- <65: 15, 65-74: 25, 75-84: N/A, 85+: N/A
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.
| Drug | Claims |
|---|---|
| Oxycodone Hcl | 30 |
| Amoxicillin-Clavulanate Potass Amoxicillin/Potassium Clav | 12 |
* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.
Registered Nurse First Assistant Overview
How Maria Kostantacos, APRN, FNP fits within the Registered Nurse First Assistant landscape nationally.
2,649
Registered Nurse First Assistant Providers in US
50
States with Registered Nurse First Assistant
419
Avg Claims per Provider
Maria Kostantacos, APRN, FNP's 84 claims are below the specialty average of 419.
Nearby Registered Nurse First Assistant Providers in Wisconsin
Other clinicians with the same primary specialty enrolled in Wisconsin, drawn from the same CMS NPPES roster as Kostantacos.
Dr. Michelle Coenen
RN
Appleton, WI
Dr. Ally Eigenbrodt
RN BSN FIRST ASSIST
Fond Du Lac, WI
Dr. Alice Fara
RN
Appleton, WI
Dr. Matthew Koeck
BSN-RN
Fond Du Lac, WI
Dr. Molly O'Neill
RN
Appleton, WI
Compare Registered Nurse First Assistant nationally: see state-by-state distribution →
Before you book an appointment
Use this federal record as your verification checklist, not as a recommendation.
- Confirm the NPI record is current in the official CMS registry, providers update their own NPPES details, and moves can lag. Verify this NPI
- Check the active license and any disciplinary history with the Wisconsin medical board, federal registration is not a license check. Credential verification guide
- Weigh a second option: compare this provider with a nearby Registered Nurse First Assistant peer on Medicare volume and prescribing patterns. Compare providers
Medicare Part D and MIPS figures describe practice patterns in federal programs only, they are not quality ratings, and PlainDoctor does not rate, rank, or recommend providers.
Healthcare Guides
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How to Find a Doctor
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Medical Specialties Explained
Who treats what and how specialties differ
Understanding Medicare Claims Data
What prescribing data reveals about a provider
In-Network vs Out-of-Network
How insurance networks affect your costs
Telehealth Guide
Virtual care options and coverage in 2026
Explore Wisconsin
Frequently Asked Questions
What is Maria Kostantacos, APRN, FNP's specialty? ▼
Maria Kostantacos, APRN, FNP specializes in Registered Nurse First Assistant and practices in Janesville, Wisconsin. Credentials: APRN, FNP.
How much does Maria Kostantacos, APRN, FNP prescribe under Medicare Part D? ▼
In 2023, Maria Kostantacos, APRN, FNP wrote 84 Medicare Part D claims totaling $854 in drug costs for 56 beneficiaries.
Where is Maria Kostantacos, APRN, FNP located? ▼
Maria Kostantacos, APRN, FNP is located at 1010 N WASHINGTON ST, Janesville, WI, 53548. Phone: (608) 741-3800.
What is Maria Kostantacos, APRN, FNP's NPI number? ▼
Maria Kostantacos, APRN, FNP's National Provider Identifier (NPI) is 1538493614, issued on 09/23/2009.
Does Maria Kostantacos, APRN, FNP prescribe opioids? ▼
Yes, Maria Kostantacos, APRN, FNP had 35 opioid claims in 2023 with an opioid prescribing rate of 41.7%.
How many Registered Nurse First Assistant providers are there in the US? ▼
There are 2,649 Registered Nurse First Assistant providers across 50 states in the US. The average Registered Nurse First Assistant provider writes 419 Medicare Part D claims per year.
What drugs does Maria Kostantacos, APRN, FNP prescribe most often? ▼
Based on 2023 Medicare Part D data, Maria Kostantacos, APRN, FNP's most frequently prescribed drugs include Oxycodone Hcl, Amoxicillin-Clavulanate Potass. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Maria Kostantacos, APRN, FNP accept Medicare? ▼
Maria Kostantacos, APRN, FNP appears in CMS Medicare data with 84 Part D claims and 56 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Maria Kostantacos, APRN, FNP's credentials? ▼
Maria Kostantacos, APRN, FNP's NPI is 1538493614 with credentials APRN, FNP. You can verify this through the NPPES NPI Registry, check state medical board records, and confirm board certification through the ABMS or AOA.
Data Sources
View source datasets and methodology notes
- Provider Directory
- CMS National Plan and Provider Enumeration System (NPPES), download.cms.gov/nppes, updated monthly. Contains NPI, specialty, credentials, and practice location.
- Specialty Classification
- NUCC Health Care Provider Taxonomy (nucc.org), the industry standard for classifying provider specialties in Medicare and Medicaid billing.
- Prescribing Data
- CMS Medicare Part D Prescriber Public Use File (2023). Includes claims, drug costs, beneficiaries, and opioid prescribing rates.
- Limitations
- Provider data is self-reported to CMS. Prescribing data reflects Medicare Part D only and does not include commercial insurance, Medicaid, or cash prescriptions. Claims below 11 beneficiaries are suppressed by CMS for privacy.
See our complete data methodology for details on how we collect and process government data.
Data as of April 2026 (NPPES) / 2023 (Medicare Part D). Source: Centers for Medicare & Medicaid Services (CMS).
Disclaimer: Data from CMS NPPES and Medicare Part D. PlainDoctor does not rate or rank providers. Provider information is self-reported and may not be current. Always verify information directly with the provider. About · Methodology
Compiled from official public sources by the PlainDoctor editorial team.