EpiPen manufacturer Mylan is now the center of a pharmaceutical industry inquiry. Following complaints from consumers, the firm had increased the cost of an emergency drug by $100 in recent months for no apparent reason. Members of Congress are calling for an investigation as the price has increased by 450% since 2004, when a dose could be bought for $100 by today’s dollar value, to its present price of more than $600.

Many consumers had not noticed the slow rise in the cost of this drug because Mylan is known to add about 9 to 15 percent each time. But with recent changes in some health plans with deductible and co-pay structures, many families have been hit by the steeper price.

EpiPens are injections used to prevent potentially deadly allergies. They are autoinjectors for injecting a calculated dose of epinephrine. It is mostly used in treating anaphylaxis.

EpiPen has a major stake in the U.S. market with about a 90% share and few opponents to speak of. This monopoly has given Mylan, a worldwide pharmaceutical growth and about $25 billion in market share. So increasing the cost of this drug is a major problem since customers have seriously restricted choices and must refill their two-pack injector supplies annually.

Sen. Charles Grassley, Representative for Iowa, wrote Mylan and asked for more information on why the cost of the device has been increased. He mentioned the value that EpiPen has for parents whose kids needed them and to schools that needed it at hand. He wanted to know why the higher price has been passed on to citizens and called for an investigation into the price increase.

Some other senators want Mylan investigated because if the reports that its executives gave themselves huge raises while increasing the price of the drug.