Mary Ann H. Trephan, MD
Emergency Medicine Physician · Northridge, CA
Mary Ann H. Trephan, MD is an emergency medicine physician with a practice address in Northridge, California, and NPI 1891752614, issued on Apr 26, 2006. Check the license (California G85040, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Mary Ann H. Trephan
- Credential
- MD
- Primary taxonomy
- Emergency Medicine Physician 207P00000X
- License number
- G85040 CA
Self-reported in NPPES; status is on the state search - Practice location
- 18300 Roscoe Blvd, Northridge, CA 91328
- Phone
- (818) 885-8500
- Enumerated
- Apr 26, 2006
- Record last updated
- Dec 1, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicaid ID
- 00G850400 CA
- Medicare enrollment
- Enrolled (PECOS I20031217001071); accepts Medicare assignment
- Medical or professional school
- Jefferson Medical College Of Thomas Jefferson University, 1993
- Entity
- Type 1 · individual
8 nearest emergency medicine physician records → All 7,751 in California → Look up another NPI →
Also registered at 18300 Roscoe Blvd
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Josephine Amissah-Addy, PAEmergency Medicine Physician1780641142
- Matthew Beatty, MDEmergency Medicine Physician1083668347
- Steven Cole, MDEmergency Medicine Physician1134186547
- Patricia Gillis, MDEmergency Medicine Physician1922058288
- Mary Grace HughesPharmacist1528425295
- Stephen JonesEmergency Medicine Physician1699732008
Verify Mary Ann H. Trephan in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license G85040Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
50% more Medicare Part D claims than the average emergency medicine physician in 2024
339 Medicare Part D claims for 252 beneficiaries, against an average of 226 among the 54,106 providers of this specialty who prescribed in Part D.
Most prescribed
- Cephalexin54 claims
- Prednisone42 claims
- Azithromycin39 claims
- Amoxicillin-Clavulanate Potass32 claims
- Albuterol Sulfate Hfa31 claims
- Moxifloxacin23 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Bills Medicare through one group practice
- Southern California Permanente Medical GroupVentura, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Mary Ann H. Trephan among 7,751 emergency medicine physician records in California
Mary Ann H. Trephan, MD is one of 7,751 emergency medicine physician records with a practice address in California. 81% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2006, is newer than 4% of them.
- NPI issued2006 · 4% of these records are older, 60% newer
- In a Medicare fileYes · 81% of these records are
- In the CMS Doctors and Clinicians fileYes · 59% of these records are
- Graduated1993 · median 2011 among the 4,560 with a school on file
- Record last updated2021 · 59% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207P00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
25 emergency medicine physician records list a practice address in Northridge
They are 25 of the 2,598 NPPES records with a practice address in Northridge, and 7,751 emergency medicine physician records in California.
All 7,751 in California → Every provider in Northridge → Emergency Medicine Physician nationwide →
The 8 emergency medicine physician records with the nearest ZIP codes
- Josephine Amissah-Addy, PANorthridge, CA 913281780641142
- Steven Cole, MDNorthridge, CA 913281134186547
- Patricia Gillis, MDNorthridge, CA 913281922058288
- Stephen JonesNorthridge, CA 913281699732008
- William Kent, PANorthridge, CA 913281508823832
- Daniel Kijner, MDNorthridge, CA 913281417913518
- Patricia MaloneyNorthridge, CA 913281881651297
- Shannon McFarland, PANorthridge, CA 913281316905953
Common questions
What is Mary Ann H. Trephan, MD's NPI number?
Mary Ann H. Trephan, MD's National Provider Identifier (NPI) is 1891752614, issued on Apr 26, 2006. An NPI identifies a provider in billing; it is not a license.
Where is Mary Ann H. Trephan, MD located?
The NPPES record lists a practice address at 18300 Roscoe Blvd, Northridge, CA, 91328. Phone: (818) 885-8500. Providers update this record themselves, so call before visiting.
How can I verify Mary Ann H. Trephan, MD's license?
NPPES lists California license number G85040, as entered by the provider. Search the Medical Board of California at https://www.mbc.ca.gov/License-Verification/default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Mary Ann H. Trephan, MD prescribe under Medicare Part D?
In 2024, Mary Ann H. Trephan, MD had 339 Medicare Part D claims for 252 beneficiaries; the average among emergency medicine physician prescribers was 226. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.