As parents check off items on the back-to-school list, many are suffering sticker shock at the price increase for EpiPens, potentially lifesaving devices that counter an allergic reaction — and that now cost more than $600.

Several factors have contributed to the pinch patients are feeling: There is no generic equivalent for EpiPens, the only competitor was taken off the market last year, and changes to high-deductible insurance plans mean much higher out-of-pocket costs for many, experts say.

A prescription cost $57 in 2007. Now sold in packages of two, EpiPens cost more than $600 for the two-pack, even though a dose of the drug itself costs less than $2, North Jersey physicians say.

“More and more parents are complaining over the last month that the cost of EpiPens has gone through the roof, making it very difficult,” said Dr. David Nam­erow, a Fair Lawn pediatrician.

“They seem to be taking advantage of the most vulnerable kids with food allergies, and the parents have no alternative,” he said.

The device allows a person to inject a dose of epinephrine — also known as adrenaline — into the thigh to stop a potentially life-threatening reaction to peanuts, eggs, other foods or insect bites. The severe reaction is known as anaphylaxis. Symptoms include swelling of the lips or tongue, shortness of breath, wheezing, dizziness and worse.

On Saturday, Sen. Amy Klobuchar, D-Minn., called on the Senate Judiciary Committee to hold hearings on the price increase.

“Patients all over the U.S. rely on these products, including my own daughter,” Klobuchar said in a statement. “Not only should the Judiciary Committee hold a hearing, the Federal Trade Commission should investigate these price increases immediately.

Up to 6 percent of children have food allergies, according to the federal Centers for Disease Control and Prevention. Studies show that up to 18 percent of children with food allergies have had a reaction after accidentally eating allergens at school, according to the CDC. Four percent of adults have food allergies.

The number of children affected is growing. The prevalence increased by 18 percent between 1997 and 2007, according to the CDC. Nearly nine in 10 schools nationally had one or more students with food allergies.

Many parents keep one EpiPen at home and send the other to school with their child. At a middle school in Ridgewood, for example, 27 EpiPens are kept in the nurse’s office — each needing to be replaced as the medication expires, said Dr. Patricia Hicks, an allergy expert at The Valley Hospital in Ridgewood.

“Parents are furious” over the cost increase, said Hicks, who also practices in Ho-Ho-Kus.

“In the last week I wrote 30 prescriptions for my patients returning to school,” she said. “Many of them need more than two.”

“How do they justify this,” Hicks asked, when the drug isn’t new?

It’s a conundrum in medicine pricing today: Even when a drug has been available for years and hasn’t been approved for any new use, costs can increase significantly. Hicks cites the increase in the price of insulin — it’s been around for decades, yet some drug companies have increased wholesale prices by more than 160 percent in the past five years, according to a 2015 Bloomberg Health Report.

A spokeswoman for Mylan, the manufacturer of EpiPens, would not comment directly on the price increases, but released a statement Friday.

“Mylan has worked tirelessly over the past years advocating for increased anaphylaxis awareness, preparedness and access to treatment for those living with potentially life-threatening allergies,” the statement said.

“Given the unpredictable and life-threatening nature of anaphylaxis, nothing is more costly than failed or no treatment.’’

The company said it provided coupons to reduce costs, and that last year nearly 80 percent of commercially insured patients paid nothing for a prescription.

Insurance companies increasingly are offering high-deductible plans, and research shows that such plans represent the only option for employees of more than one in five companies. Insurers note that when consumers select plans, they often opt for higher deductibles in exchange for the benefit of lower premiums.

Dr. Evelyn Hermes-DeSantis, a clinical professor at the Ernest Mario School of Pharmacy at Rutgers University, attributed the price increases for EpiPens to the virtual monopoly Mylan has on the drug. After a competitor voluntarily pulled its product from the market last October because of dosing problems, that left only Adrena­click, a device that delivers the same drug as EpiPen but that is harder to use.

The FDA doesn’t consider Adrenaclick “therapeutically equiv­alent,” so doctors won’t write the prescriptions unless patients ask for it, and insurers may not pay, physicians say. At around $400 for two devices, “it’s cheaper but it’s still pricey,” Hermes-DeSantis said. A generic version of Adrenaclick is available, but the same issues over ease of delivery of the medication are a factor, she said.

A spokesman for Impact Laboratories, the drug maker that produces Adrenaclick, said the devices are produced manually and the supply is limited. “We are investing in automation,” said Mark Donohue, a vice president and spokes­man. “We’re trying to produce as much as we can, and it’s a lower-cost option.”

Dr. Mary Ann Michelis, chief |of allergy and immunology for ­pediatrics and internal medicine |at Hackensack University Medical Center, acknowledged that drug makers “can charge whatever |they want,” and that she had |heard complaints from many patients.

“The second factor here is the absurd charges by insurance companies through their deductible policies,” Michelis said. “You have relatively young people and the cheapest insurance they can get has deductibles from $1,500 up to several thousands of dollars. There is no way a healthy kid is going to eat up that deductible, so parents are paying the full cost.”