Margaret Essex Castor, WHNP
NPI 1275960585ActiveIndividual· Nurse Practitioner, Women's Health· Phoenix, AZ
Nurse Practitioner, Women's Health (WHNP) in Phoenix, Arizona, trained at Vanderbilt University School of Medicine (class of 2013). Mostly services rather than prescriptions: Medicare paid $6,683 for 28 patients in 2024, with only 46 Part D claims. Biogen, Inc. was the largest of 8 companies reporting payments in 2025, $280.63 in all, mostly food and beverage.
Overview
| NPI | 1275960585 |
|---|---|
| Status | Active |
| Entity type | Individual |
| Credential | WHNP |
| Sole proprietor | No |
| NPI issued | Oct 1, 2013 |
| Last updated in NPPES | Feb 4, 2026 |
| Certified by provider | Feb 4, 2026 |
Specialties and licenses
| Taxonomy | Code | License | State |
|---|---|---|---|
| Nurse Practitioner, Women's Health Primary | 363LW0102X | 300500 | AZ |
| Registered Nurse | 163W00000X | 300500 | AZ |
Exclusion screening
| List | Result | Details |
|---|---|---|
| HHS-OIG LEIE · Nov 10, 2026 | No match | Checked by NPI and by name + state |
| North Carolina Medicaid · Nov 11, 2026 | No match | — |
| New York OMIG · Nov 11, 2026 | No match | — |
| Ohio Medicaid · Nov 11, 2026 | No match | — |
| Pennsylvania Medicheck · Nov 11, 2026 | No match | — |
| Washington HCA · Nov 11, 2026 | No match | — |
Official OIG search · How matching works ·Bulk check a roster
Medicare
| Enrollment (PECOS) | Enrolled Practitioner - Nurse Practitioner (AZ); Practitioner - Nurse Practitioner (IN) |
|---|---|
| Accepts assignment | Yes (participating) |
Medicare services in 2024
| Medicare patients | 28 |
|---|---|
| Services billed | 249 across 17 procedure codes |
| Paid by Medicare | $6,683 |
Part D prescriptions in 2024
| Prescriptions (claims) | 46 · 74 30-day fills |
|---|---|
| Patients | 24 |
| Total drug cost | $1,818 |
| Generic share | 85% of claims |
Education and affiliations
| Medical school | Vanderbilt University School of Medicine |
|---|---|
| Graduation year | 2013 |
| Medicare specialty | Nurse Practitioner |
Medical group
- Genesis OB GYN PLLCOro Valley, AZ · 110 clinicians
Industry payments (Open Payments)
- 2025$280.63 · 15 payments from 8 companies
- 2024$117.63 · 7 payments from 7 companies
Top paying companies in 2025
| Company | Amount | Payments |
|---|---|---|
| Biogen, Inc. | $73.60 | 3 |
| Pfizer Inc. | $36.63 | 2 |
| Mayne Pharma Commercial LLC | $35.21 | 2 |
| Organon LLC | $33.80 | 2 |
| Bayer Healthcare Pharmaceuticals Inc. | $32.64 | 2 |
What the 2025 payments were for
- Food and Beverage$280.63 · 15 payments
Receiving payments does not imply wrongdoing. What Open Payments covers ·original records
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All 91 women's health nurse practitioners in Phoenix · All women's health nurse practitioners in Arizona