The Massachusetts House has taken a “crucial step” toward lowering the costs of some of the most frequently prescribed drugs, with new rules that could see some diabetes, asthma, and heart disease medications provided at no cost to patients.

On Wednesday, and with just a week to go before their formal session ends for the year, lower-chamber lawmakers unanimously passed An Act relative to pharmaceutical access, costs and transparency, adding yet another proposal to the pile of bills to be reconciled with their Senate colleagues.

The bill, according to Rep. John Lawn, of Watertown, would dramatically change the cost of prescription drugs in the Bay State by “shedding light on pharmacy benefit managers, whose deceptive practices increase drug prices, decrease transparency and harm consumers and independent pharmacies.”

“Three of the top 20 Fortune 500 companies are PBMs, and they use a number of unsavory business practices to increase drug prices, decrease transparency, and harm patients and independent pharmacies,” Lawn said.

The House bill would address three of the industry’s “most egregious practices” by banning or limiting spread pricing, rebates, and clawbacks, Lawn said.

Spread pricing, he explained, is when a middleman — that’s the PMBs — in between an insurer and a pharmacy charges the pharmacist more for prescription drugs than the insurer is paying.

“In quarter four of 2018, MassHealth MCOs paid an average of $159 per generic prescription, compared to average fee-for-service price of $75,” Lawn said.

If accepted by the senate as written and made law, the bill would impose a three-year license requirement on PBMs doing business in the commonwealth, would mandate audits of PMBs by the Massachusetts Division of Insurance during each three year period, and “provides for periodic audits by health insurers who contract with PBMs.”

The bill would also require insurers and PMBs and health insurers to send 80% of rebates received by either entity to consumers at the point of sale.

Under the house plan, insurance carriers would be required to identify “one generic drug and one brand name drug” used in the treatment of the asthma, diabetes, and heart disease. The bill would the reduce the cost of those drugs to zero or no more than about $300 annually.

“There will be no copays for generic drugs. For brand name drugs, copays will be capped at $25 for a 30-day supply,” Lawn said.

According to information provided by CVS, PBMs play an important roll in health care, helping to “manage prescription drug benefits for clients ranging from health insurers and Medicare Part D drug plans to large employers. PBMs are one of the few parts of the prescription drug supply chain specifically dedicated to lowering costs.”

Danvers’ state Rep. Sally Kerans said that’s not what patients are telling lawmakers. The bill is a “crucial step” toward protecting Bay State consumers, she said.

“I was jarred at a hearing last year, as were my seatmates — we all were — as we listened to people who had been strung up by these pharmacy benefit management practices and blocking their access to life-saving or health-saving medications,” she said. “This bill brings PBMs to heel by increasing transparency of their business practices through regular oversight of the health policy commission, banning clawbacks, banning spread pricing and more.”

The bill heads back to the Senate, where there are already half-a-dozen House passed bills waiting for action. A further half dozen bills have been passed by both the House and Senate and are now locked in joint conference committee negotiations. The Legislature’s formal session ends on July 31.