PORTLAND, Maine — Apothecary by Design, the independent pharmacy based in Bayside, has been sold to a privately held New York investment firm.

“We want to continue to grow and advance, they are an excellent partner to provide that capital to do that,” Mark McAuliffe, Apothecary by Design chief executive, said Monday about the sale to BelHealth Investment Partners.

The sale was completed Aug. 17. McAuliffe declined to disclose the price, but said he and other company officials will remain minority shareholders; BelHealth has the majority stake.

The new capital will fund expansion along the East Coast. Growth in the south and west are also a part of the company’s plans.

“The patients should see no difference, it is just to expand the model,” McAuliffe said.

The acquisition was praised last month by BelHealth Managing Partner Harold S. Blue.

“We are excited to partner with the founders of ABD to help them penetrate new markets and strengthen their already impressive business,” Blue said in a press release. “The company has established a strong presence within their geographic community and we look forward to working with the company and founders to continue to expand our footprint nationally.”

According to its filings with the U.S. Securities and Exchange Commission, BelHealth is considered a “large advisory firm” managing more than $90 million in assets. It is based in Manhattan, and has an office in Newport, California. The company lists eight employees, seven of whom “perform investment advisory functions.”

The SEC filings show BelHealth provided “investment advisory services” to no more than 10 clients in the last fiscal year.

BelHealth said it invests anywhere from $20 million to $50 million in “platform” companies in the areas of products, services and distribution.

BelHealth has also invested in Linden Care, based in Woodbury, New York. That company specializes in “pharmacy services to the pain management industry,” according to a Linden Care press release.

McAuliffe said BelHealth’s expertise and additions to the ABD board of directors are critical to make expansion succeed.

“They have owned a number of specialty pharmacies, so they are very knowledgeable in the industry,” he said.

ABD has “a focus on advocating for patients with chronic, complex diseases,”according to a press release. Specialty areas include HIV, hepatitis C, multiple sclerosis and infertility treatments.

McAuliffe said the company compounds its own medicines, but mostly sells prescription drugs not handled by more ordinary pharmacies.

“The overwhelming percentage of what we do is specialty drugs the drug manufacturers make,” he said.

The medications can cost $3,000 per month or more. McAuliffe said Harvoni, a highly effective drug in combating hepatitis C, which damages the liver, can cost $30,000.

“These are expensive drugs,” he said.

ABD has offices at 141 Preble St. and a pharmacy at 84 Marginal Way. It began with 12 employees and now has 85.

Its roots will remain local, McAuliffe said.

“There will still be a lot of work coming back to and managed through Portland,” he said.