A single, 5,000 percent price hike on an anti-parasitic drug made by Turing Pharmaceuticals garnered national media attention. But it’s just one of hundreds of smaller price increases drug companies make in the U.S. each year, a tactic the industry uses to generate more revenue from older medications.

Pfizer Inc., the nation’s biggest drugmaker, has raised prices on 133 of its brand-name products in the U.S. this year, according to research from UBS, more than three-quarters of which added up to hikes of 10 percent or more. It’s not alone. Rival Merck & Co. raised the price of 38 drugs, about a quarter of which resulted in increases of 10 percent or more. Pfizer sells more than 600 drugs globally while Merck has more than 200 worldwide, including almost 100 in the U.S.

Drugmakers have long said these increases aren’t felt by most consumers because intermediaries like insurers negotiate what is ultimately paid -- meaning what they really charge for their drugs is far below the list price. Pfizer and its rivals say they can’t make those negotiated prices public for competitive reasons.

Like its competitors, Pfizer has been raising prices on older drugs in its portfolio for years. The increases in the U.S. have added $1.07 billion of quarterly revenue from mid-2012 to the middle of this year, helping limit the company’s total decline in quarterly revenue over that time period to $2 billion even as patents on blockbuster drugs expired, according to estimates from SSR, an investment research firm. In the case of Bristol-Myers Squibb Co., increasing the price of existing drugs in the U.S. brought in $435 million of revenue over the past three years, leaving the contraction of the company’s global sales at $280 million, SSR estimates show.