NEW YORK — New York on Thursday will join 22 other states when it formally launches its medical marijuana law. Signed by Gov. Andrew Cuomo in November, the Compassionate Care Act allows doctors to prescribe oil extracts of the cannabis plant for patients with chronic or severe ailments such as HIV/AIDS, Parkinson’s disease or spinal cord injuries.

But drug reform advocates say the narrow terms of the law mean medical cannabis will be out of reach for many patients who need it to ease physical and mental pain.

The dearth of dispensaries — 20 are slated to open in a state with nearly 20 million people — will further complicate access, reform advocates say. Patients and family members might have to travel long distances to get to a dispensary or a doctor who has the credentials to prescribe marijuana.

“It’s among the most restrictive medical marijuana laws in the country,” said Karen O’Keefe, director of state policies for the Washington, D.C.-based Marijuana Policy Project, a drug reform advocacy group.

“Unfortunately, it seemed like the priority was to make it as limited as possible, instead of focusing on what is best for patients,” O’Keefe said.

Cuomo said during the bill's passage through the legislature that New York must take a cautious and calculated approach to marijuana reform.

By contrast, California’s medical marijuana law, passed by voters in 1996, allows doctors to distribute medical marijuana licenses as they see fit, and hundreds of dispensaries carry smokable and edible marijuana products.

New Yorkers will only be able to obtain prescriptions from doctors who have attended a state-mandated training course. For many patients, these physicians are likely not their own doctors. There’s no provision in the law providing a price break for poor patients, although distributors can offer discounts.

“I live on SSDI [Social Security] and have real concerns about whether I and people like me are going to be able to pay for this medicine,” said Nancy Rivera, of Troy, New York, according to a press release from the Drug Policy Alliance, a pro-legalization group. “Insurance won’t cover this, and the last thing I want to see is a program that only the rich can afford.”

But Nick Vita, CEO of Columbia Care, one of five medical marijuana companies that will be allowed to dispense the drug in New York, said his firm is motivated by altruism and good corporate citizenship, not pure profit. The New York law allows Columbia Care and four other firms to grow, process and sell cannabis extract, referred to as “product” by Vita and his staff.

Since Columbia Care is a privately held company, Vita said he doesn’t have to answer to shareholders and can offer generous financial aid to patients.

“We have a shared care/financial subsidy program that ensures that if patients come, they will be able to afford the product,” Vita said, noting that 20 percent of patients at its Washington, D.C. facility receive some form of lower-cost medicinal marijuana.

As for the issues drug reform advocates have raised with New York’s law, Vita said Columbia Care doesn’t intercede in local pot politics.

“We don’t take a position on that,” he said. “Our view is that policy makers will operate at their own pace. This is a marathon, not a sprint.”

Reform advocates say the New York law has a long way left to go, especially regarding wounded veterans. Qualifying ailments do not include Post Traumatic Stress Disorder (PTSD), which often afflicts soldiers after traumatic experiences in service. Medical marijuana studies have shown that medical cannabis that can help treat symptoms commonly associated with PTSD, such as nightmares and anxiety.

“Many states with medical marijuana cover PTSD. There’s recognition in the medical community that it can alleviate PTSD,” said Julia Netherland, academic engagement director at the Drug Policy Alliance.

Reform advocates point out that New York does not allow voters to enact or amend laws through referendum or initiative. If it did, they say, widespread support among New Yorkers for medical marijuana would have resulted in the passage of a less-restrictive law.

A 2014 Quinnipiac University poll found that 88 percent of New York residents support the legalization of medical marijuana. National polls also show that a majority of Americans back medical marijuana.

New York reform advocates, however, say that the New York law represents at least a small step in the right direction, and that regulators may soon lessen some of the measure’s restrictions.

Such change could come as early as Thursday, a deadline for the state’s Health Commissioner, Howard A. Zucker, to decide whether to add PTSD, Alzheimer's disease, muscular dystrophy, dystonia and rheumatoid arthritis to the list of ailments approved for medical marijuana.

“He also has the ability to add any condition at any time,” Netherland said, referring to Zucker. “We hope he’ll do the right thing.”