I would search forums like reddit.com/r/pharmacy or /r/medicine or sdnforum
For example
https://www.reddit.com/r/pharmacy/comments/33ac79/what_is_th...
But you can ignore a lot of the complexity these days due to consolidation. What used to be a health insurance company selling insurance for medical procedures only, and outsourcing the task of of evaluating coverage and negotiating prices for medicines to a third party known as pharmacy benefit managers, PBMs, is many times no longer outsourced.
Hence the term "managed care organization" (MCO) to supplant "health insurance company". Because now, the same business that sells the insurance can also employ the pharmacist, negotiate pricing for medical procedures and medicines, and employ the doctor providing the healthcare in some cases.
From a patient perspective, you and/or your employer pay the MCO, the MCO pays the doctor and/or pharmacist if the service/medicine is covered, and you pay the deductible/copay and this counts towards your out of pocket maximum.
Kaiser Permanente is an MCO that owns healthcare delivery from hospital to doctors to pharmacies. Some MCOs own more of the healthcare chain than others, and on the other side, you have hospital and doctor groups consolidating to be able to negotiate more favorable terms with increasingly larger MCOs.
The pharmacy pays the medicine distributor (such as Cardinal or McKesson or Amerisource Bergen), and the medicine distributor pays the medicine manufacturer (Pfizer, Merck, NovoNordisk, etc).
Most pharmacies themselves are owned by huge entities. Such as the largest retail pharmacy, CVS, which itself is an MCO. Next up is probably Walmart, Kroger, Costco, Albertsons, and then you have the last 2 big standalone retail pharmacies, Walgreens and Riteaid.
Looking at market capitalization graphs for Walgreens and Riteaid will inform you of how "up or out" the business is.