Why prescription drugs prices going up — Here are 5 reasons why this issue is back:

In this year’s presidential campaign, health care has taken a back seat. But one issue appears to be breaking through: the rising cost of prescription drugs.

The blockbuster drugs to treat hepatitis C as well as dramatic price increases on older drugs, most recently the EpiPen allergy treatment, have combined to put the issue back on the front burner.

Republican Donald Trump, meanwhile, has said little about health care since announcing his candidacy in 2015, but he has several times called for a change in law to allowMedicare to negotiate drug pricesfor the population it serves.

Here are five reasons why this issue is back — and why it is so difficult to solve.

There are multiple, often unrelated reasons that drug prices are going up.

One is the introduction of brand-name blockbuster drugs, such as Sovaldi and Harvoni. They effectively cure hepatitis C — but at a total cost of more than $80,000. Federal statisticians singled out the hepatitis C medications as a key reason prescription drug spending increased by 12.2 percent in 2014, up from 2.4 percent the year before.

Congress first addressed the issue of rising drug prices in 1984, when it passed abipartisan bill that made it easier for generic copies of brand-name drugs to be approved. But lawmakers also gave brand-name drugmakers more time without generic competition by allowing them to keep their products on their patents longer to make up for often years-long approval process at the Food and Drug Administration.

In 1990, concern about rising medication costs to the Medicaid program, the joint federal-state insurance coverage for low-income residents, led to a law requiring drugmakers to provide significant discounts.

During the late 1990s and early 2000s, Congress repeatedly debated the idea of lowering drug prices by allowing consumers to purchase drugs that were brought in from other industrialized countries that impose price controls. A few such “reimportation” proposalswere passed into law. But the laws required certification by federal health officials and both Democratic and Republican administration officials blocked the efforts, which they said threatened the safety of the U.S. drug supply.

A dramatic increase in use of generic drugs for the next several years helped keep the cost of the new Medicare benefit in check, and kept drug prices mostly off the political front burner.

But now, not only are prices rising again, but many people also have insurance that requires them to pay more out-of-pocket for drugs. Those patients complain, in turn, to lawmakers, who feel the need to address the issue.

It is not clear what would work to fix drug price problems, but it is pretty clear what would NOT.

Both Clinton and Trump have endorsed a change in the law to allow Medicare to negotiate drug prices, a practice that is currently banned.

In California, meanwhile, voters this fall will face a proposal to ban state health programs from paying any more for drugs than the price at which they are sold to the Veterans Health Administration, which gets large discounts, but also covers only a limited list of drugs. The proposal is strongly opposed by the drug industry, but even some likely supporters have raised questions about whether it would work.

On the other hand, the pharmaceutical industry remains one of themost powerful forcesin Washington, not to mention many state capitals. Drug industry lobbying has blocked efforts to allow people to buy cheaper drugs from overseas, ensured that the Medicare prescription drug benefit did not allow the federal government to set or negotiate prices, and kept efforts to rein in drug prices out of theAffordable Care Act.

As a result, wrote three Harvard Medical School researchers in a comprehensive look at the drug price issue in the Journal of the American Medical Association, “prescription drugs are priced in the United State primarily on the basis of what the market will bear.” Attempting to set prices or otherwise constrain industry profits, they added, “would have major marketplace ramifications and is not at present politically feasible, in part because of the power to the pharmaceutical lobby in Washington, D.C.”