Mark Castellaw, MD
Internal Medicine · Germantown, TNNPI 1114928793
Payments from drug & device makers
Across 276 payments — averaging $16.42 each. Meals, travel, consulting and speaking fees, gifts and royalties reported by drug and device makers.
- Novo Nordisk$2K
- Lilly USA, LLC$378
- Novartis$331
- AstraZeneca$280
- Abbott$269
- Amgen$237
- plus $2K from 21 others
What the payments were for
- Food & beverage$4,516100%
- Education$170%
Most of this is food and beverage — typically meals provided during product presentations at a clinic or hospital. Nationally that is the single largest category of reported payments by count.
General payments by program year
Who reported the general payments
Companies are grouped under their corporate parent — a single manufacturer often files under several CMS reporting entities. Research and ownership payments are counted separately and are not in this table.
| Company | Payments | Total |
|---|---|---|
| Novo Nordisk | 86 | $1,524 |
| Lilly USA, LLC | 31 | $378 |
| Novartis | 20 | $331 |
| AstraZeneca | 21 | $280 |
| Abbott | 13 | $269 |
| Amgen | 14 | $237 |
| Pfizer | 15 | $230 |
| Astellas Pharma US Inc | 10 | $182 |
| AbbVie(2 entities) | 10 | $164 |
| Sanofi-aventis U.S. LLC | 8 | $117 |
| Amarin Pharma, Inc. | 7 | $106 |
| GSK | 5 | $104 |
| Biohaven Pharmaceuticals, Inc. | 2 | $87 |
| Bayer | 5 | $80 |
| Takeda Pharmaceuticals U.S.A., Inc. | 5 | $76 |
| Boehringer Ingelheim | 5 | $75 |
| Biohaven Pharmaceutical Holding Company Ltd. | 5 | $72 |
| Johnson & Johnson | 3 | $37 |
| Xeris Pharmaceuticals, Inc. | 2 | $31 |
| Seqirus USA Inc | 1 | $30 |
| Merck | 2 | $28 |
| Hologic Sales And Service, LLC | 1 | $18 |
| Genentech USA, Inc. | 1 | $16 |
| Averitas Pharma Inc. | 1 | $16 |
| Currax Pharmaceuticals LLC | 1 | $16 |
| Phathom Pharmaceuticals, Inc. | 1 | $15 |
| Nevro Corp. | 1 | $14 |
How this compares
$4,532 in reported general payments places this provider in the 85th percentile of 2,216 internal medicine providers in Tennessee.
Medicare billing
What this is not: this is the amount Original Medicare Part B allowed for services this provider billed in 2024. It is not their income. It excludes Medicare Advantage — now more than half of all Medicare enrollment — along with Medicaid and all commercial insurance, and it is gross practice revenue before staff, rent, supplies and malpractice premiums. CMS also suppresses any figure covering ten or fewer patients, so low-volume providers appear smaller than they are.
Most prescribed under Part D
| Drug | Claims | Cost to plans & patients |
|---|---|---|
| OzempicSemaglutide | 222 | $252,613 |
| MounjaroTirzepatide | 116 | $133,201 |
| EliquisApixaban | 82 | $78,043 |
| JanuviaSitagliptin Phosphate | 56 | $61,217 |
| JardianceEmpagliflozin | 46 | $47,263 |
| TrulicityDulaglutide | 19 | $26,875 |
| Toujeo SolostarInsulin Glargine,hum.Rec.Anlog | 27 | $26,051 |
| Tresiba Flextouch U-200Insulin Degludec | 31 | $25,484 |
| XareltoRivaroxaban | 16 | $20,759 |
| Tresiba Flextouch U-100Insulin Degludec | 30 | $20,275 |
| JanumetSitagliptin Phos/Metformin Hcl | 17 | $18,655 |
| ArexvyRsvpref3 Antigen/As01e/Pf | 41 | $11,409 |
| Lantus SolostarInsulin Glargine,hum.Rec.Anlog | 52 | $10,726 |
| Ezetimibe | 394 | $9,763 |
| FarxigaDapagliflozin Propanediol | 13 | $8,139 |
Paid to pharmacies, not to this prescriber.
Companies that both paid and supply prescribed drugs
These companies both reported payments to this provider and make drugs the provider prescribed under Medicare Part D in 2024. For most specialties this overlap is expected — a cardiologist who is paid by a cardiology drugmaker also treats heart disease. It is shown so the reader can see it, not because it implies anything on its own.
| Company | Paid to this provider | Part D cost of their drugs |
|---|---|---|
| Novo NordiskOzempic | $1,524 | $252,613222 claims |
| Lilly USA, LLCMounjaro, Trulicity | $378 | $160,075135 claims |
| MerckJanuvia, Janumet | $28 | $79,87173 claims |
| PfizerEliquis | $230 | $78,04382 claims |
| Boehringer IngelheimJardiance | $75 | $47,26346 claims |
| Johnson & JohnsonXarelto | $37 | $20,75916 claims |
| GSKArexvy, Shingrix | $104 | $15,13260 claims |
| AstraZenecaFarxiga | $280 | $8,13913 claims |
| AbbVieSynthroid | $164 | $3,65243 claims |
Reading this fairly. The Part D column is what drug plans and patients paid pharmacies — this provider received none of it, and it reflects how many patients they treat and what those drugs cost. Against peers, this provider's reported payments sit in the 85th percentile of 2,216 internal medicine providers in Tennessee.
Other internal medicine in Germantown
- Mark McKenzieChattanooga$11.9M
- Bernard GrunstraBristol$6.4M
- Jewel WhiteKingsport$5.7M
- Judith WhiteKingsport$5.6M
- Obadias MarquezOoltewah$2.8M
- Amanda Moore MillerKnoxville$2.3M
- Rick WhilesBristol$1.5M
- John AndersonNashville$1.5M
- David MorinKingsport$1.4M
- John KirbyJefferson City$1.2M
Where these figures come from
- Payments: CMS Open Payments, program years 2019–2025 (publication P06302026_06032026).
- Billing: Medicare Physician & Other Practitioners, data year 2024. Original Medicare Part B only.
- Identity: NPPES NPI Registry, July 2026.