Vets First Choice, the Portland company that offers online pharmacy services for veterinarians, has raised $52.3 million from a group of new and existing investors, according to a filing with the U.S. Securities and Exchange Commission.

The equity investment was raised from 33 investors, according to the document, signed by CEO Benjamin Shaw and dated July 15, 2015. The investment was officially made in Direct Vet Marketing, which is doing business as Vets First Choice.

The company, which was founded in 2008, offers customized online pharmacy services that veterinarian practices can offer their customers.

Further details about the equity investment were not immediately available, but it’s known that the major new investor is Clayton, Dubilier & Rice, an investment firm with offices in New York City and London.

Vets First Choice announced on July 2 a “significant investment” from CD&R and existing shareholders that would “accelerate and expand the company’s services.” The amount of that investment was not revealed until this week’s SEC filing.

“We are excited for the opportunity to partner with the CD&R team to scale our network of veterinary practice partners, support the launch of new services and pursue strategic business development opportunities,” Shaw said in a statement.

Ravi Sachdev, a partner at CD&R, has joined Vets First Choice’s board.

“Vets First Choice has become an indispensable service to veterinarians,” Sachdev said in a statement. “All of us at CD&R are very excited to partner with this proven management team to unlock significant value via new technology and services powered by the Vets First Choice platform.”

The company has grown steadily over the last several years. It has made Inc. magazine’s list of the 5,000 fastest growing public companies for the past three years. On last year’s Inc. 5,000 list, the company reported 2013 revenue of $18.7 million, which represented 573 percent growth from its 2010 revenue of $2.8 million. It reported having 85 employees in 2013.

CrunchBase, which maintains a database of venture capital deals, lists Vets First Choice as having already raised $10.5 million in two rounds. Existing investors in the company include HLM Venture Partners, Polaris Partners, Borealis Ventures, Harbor Light Capital and Black Point Group, the Maine-based investment firm launched by Shaw and his father, IDEXX founder David Shaw.