Over the past few years, the blockbuster antihistamine Claritin has become almost as ubiquitous as aspirin, used by millions of American allergy sufferers.

But unlike with aspirin, only one company, New Jersey pharmaceutical giant Schering-Plough Corp., gets the revenue from Claritin sales, which totaled $1.9 billion last year.

Now, Congress faces a question with huge implications for both Schering-Plough and drug consumers: Should Schering-Plough be able to control Claritin and its profits for years into the future, or should competition from cheaper generic versions be allowed sooner?

For three years, the company has used a multimillion-dollar lobbying campaign to try to get help from Congress in protecting the Claritin patent beyond its 2002 expiration date.

The latest attempt is a bill that would let Schering-Plough and a few other companies plead their case for three years of added life before a special patent review board. The company just wants a fair hearing, chief executive Richard Jay Kogan told a Senate hearing in August.

But Schering-Plough's battle to win passage of the measure this year has taken on larger dimensions. Opponents have cast it as a test of corporate influence versus Congress's concern that drugs be made more affordable, especially for uninsured seniors who must pay full price.

A dose of Claritin costs between $1.80 and $2.66 retail, which for many users is largely absorbed by insurers. Generic drug manufacturers say they can make an equivalent for about 50 cents.

Rep. Henry A. Waxman (D-Calif.), an advocate for low-priced generics, calls the proposal the "Claritin Monopoly Extension Act." Its passage, he said, "would send a simple message that if you spend enough money and hire the right lobbyists you can get a law that harms consumers."

The importance to both sides is obvious from the intensity of the fight. Since 1996, Schering-Plough has doubled its lobbying spending to $4 million a year, adding several familiar faces to woo Democratic support, including Peter Knight, a confidant of Vice President Gore, and Linda Daschle, the wife of Senate Minority Leader Thomas A. Daschle (D-S.D.).

The company has made other gestures large and small: a $1 million donation to the foundation of supporter C. Everett Koop, the former surgeon general; an outpouring of campaign donations; use of its Gulfstream IV corporate jet by a key senator; and free Baltimore Orioles tickets.

Though outgunned, the makers of generic drugs have fought back, even launching personal attacks on the patent legislation's sponsors.

Schering-Plough is not the only drug company to turn to Congress for patent help in recent years, but it stands out for its sheer persistence.

The company's problem began in 1984, when the drug was moving slowly through the Food and Drug Administration approval process. That year, Congress passed a Waxman-sponsored bill opening the market more for generics.

To lessen the impact on brand names, Congress built in a concession. It granted patent extensions of up to five years to drugs that were not yet in clinical trials. Those further along in the FDA pipeline, such as Claritin, got only two extra years because approval was considered imminent.

But several years passed and still Claritin waited. Schering-Plough's Kogan said the short-staffed FDA put his product at the "back of the line" because it was not a potentially lifesaving drug. An FDA spokeswoman acknowledged delays but said there were substantive questions about the product.

Claritin was finally approved in 1993, and U.S. sales soared to nearly $900 million by 1996. But its very success created controversy.

A few insurers balked at Claritin's costs and ordered higher co-payments for Claritin purchasers, a way of pushing less expensive alternatives such as nasal sprays. (George Washington University's health plan, for example, removed Claritin from its preferred drug list in July).

Schering-Plough argued that Claritin profits help fund vital drug research and development. Foes of the patent extension point out that the firm reported $1.8 billion in profit last year, even after its $1 billion research and development spending.

Makers of generic drugs are eager to break into the prescription allergy medicine market, which has grown 600 percent in five years, according to a recent study. But Schering-Plough is vigilant. It already has sued some generic firms, claiming they are infringing on Claritin patents.

Schering-Plough's appeal to Congress began in the spring of 1996, not long after drugmaker G.D. Searle & Co. won a patent extension for its arthritis drug, Daypro.

For years, Schering-Plough had used the lobbying services of a firm headed by former Senate majority leader Howard H. Baker Jr. (R-Tenn.). But that year it began hiring what became an army of a dozen other lobbying firms.

Its first tack was to persuade Sen. Arlen Specter (R-Pa.), an Appropriations Committee member, to try to attach a two-year Claritin patent extension to the Agriculture Department spending bill. Such maneuvers are often used by members to slip in controversial measures, but Specter's effort failed.

In early 1997, Schering-Plough's in-house lobbyist, Robert Lively, began pushing the notion of a patent review board. The approach would take "the issue out of politics," said company spokesman William O'Donnell.

Opponents argued that Congress would merely be signaling its endorsement, which would be hard for a review board to ignore.

To float the idea, the company turned to Sen. Fred D. Thompson (R-Tenn.), whose state is home to two Schering-Plough facilities, and then to home-state Sen. Robert G. Torricelli (D-N.J.). But they stopped short of introducing legislation.

Claritin's U.S. sales in 1997 soared to $1.4 billion, helped by an FDA decision to make it easier for drug companies to advertise directly to consumers. Claritin's advertising campaign was massive, costing nearly $200 million last year.

Last fall, Schering-Plough went to New Jersey's other senator, Frank R. Lautenberg (D), who tried to attach the review board provision to a late-session omnibus spending bill. A Lautenberg spokesman said he helped because the company is important to New Jersey's economy.

Public interest groups and lobbyists for the generics industry again complained about stealth tactics. That was when Koop, a respected voice on Capitol Hill, entered the picture.

Last Oct. 13, he wrote members, saying the proposed legislation "merely creates a fair, open process." Still, the effort failed.

This year, Claritin's maker changed its approach again, pushing for public debate on the issue. It persuaded Torricelli to introduce a Senate bill--the day after Schering-Plough contributed $50,000 to the Democratic Senate campaign committee he chairs. The timing was a coincidence, a company spokesman and a Torricelli aide said.

In the House, Reps. Edward G. Bryant (R-Tenn.) and Jim McDermott (D-Wash.) co-sponsored a Schering-Plough bill. The next day, Koop sent another letter to members praising the measure.

Meanwhile, Schering-Plough also shifted its political giving. Historically, the firm's political action committee (PAC) favored Republicans. This year through June, more than half its donations flowed to Democrats. A similar change occurred in its "soft money"--corporate donations to political parties.

McDermott's support shocked consumer groups, which consider him an ally. A psychiatrist, he supports national health insurance and has advocated cheaper drugs for seniors. Schering-Plough's PAC has donated to McDermott's campaigns for years and lobbyist Lively has supplied the House member with Baltimore Orioles tickets as an in-kind political contribution.

David Schaefer, a spokesman for McDermott, said McDermott believes allowing a patent hearing is better than trying to sneak extensions into bills "in the middle of the night." McDermott considers Schering-Plough a "good corporate citizen," the spokesman added. In the early 1990s, it supplied him with antibiotics on overseas health care missions.

Schaefer said McDermott was miffed when one segment of the generic drugs industry got personal. It sponsored attack radio ads in McDermott's district, asking constituents to send in $1 bills to "Buy Jim Back" by matching $7,000 in Schering-Plough donations.

The tension between the sides was also in evidence June 10, in a Capitol basement hallway. C. McClain Haddow, a lobbyist for generics maker Mylan Laboratories, needled former surgeon general Koop as he waited to talk about "fairness in drug patenting."

"Come on, Chick! You can't tell me Schering isn't helping you out on one of your programs," Haddow recalled telling Koop. Later, he learned about Schering-Plough's $1 million donation to Koop's foundation. The company and a Koop aide said the gift was not related to his advocacy.

In July, Sen. Orrin G. Hatch (R-Utah) scheduled a hearing on the Torricelli bill. He had just announced a presidential bid, and asked Schering-Plough for the use of its Gulfstream executive jet for campaign travel, according to spokesman Jeff Flint.

Federal campaign rules allow a candidate to use a corporate jet for the price of a first-class airline ticket, which is less than it costs the company to operate the plane.

O'Donnell said Schering-Plough historically has made its aircraft available to members of Congress "on a very limited basis." Hatch's spending report shows he has paid for use of the drugmaker's jet five times. One payment was made the day after the hearing, for what Flint said was a trip to Iowa.

O'Donnell and Flint both said Hatch's use of the plane had nothing to do with his decision to hold the hearing.

Now, Schering-Plough's proposal seems stalled in Congress's waning days, but the two sides continue to jockey for position. On Tuesday, four more House members agreed to co-sponsor the Bryant-McDermott bill.

And last month, a seniors group persuaded Sen. Conrad Burns (R-Mont.) to drop his co-sponsorship of Torricelli's bill. "I would be blocking patient access to generic medications for three more years, forcing millions of Americans to pay inflated prices for these drugs," he said.

Earlier this week a collection of labor, consumer and seniors groups wrote members of Congress, asking them to be on watch for stealth attempts to attach the Claritin bill to must-pass appropriations bills at the end of the session.

If Schering-Plough fails again, Public Citizen's Maura Kealey said, "be assured they will be back next year."

Staff researcher Alice Crites contributed to this report.

JUMP INFORMATION APPENDED FROM FILE

Schering-Plough's Political Voice in Washington 1996-1999

Lobbying -- Schering-Plough spent less than $2 million on lobbying in 1996, the year it first tried to get a patent extension for Claritin. It doubled its lobbying expenditures to more than $4 million last year, and spent another $2.2 million in the first six months of this year. The firm of former Senate majority leader Howard Baker (R-Tenn.) has represented Schering-Plough for years, but the company has added a dozen other lobbying firms to its roster since mid-1996.

Campaign donations -- Though Schering-Plough, like many corporations, has historically given the majority of its political action committee (PAC) and unlimited "soft money" donations to Republican candidates and committees, its recent giving has matched its effort to get bipartisan support for the patent extension. In the 1996 and 1998 election cycles, three-fourths of its PAC donations went to Republicans; in the first six months of this year, 61 percent went to Democrats, according to Public Disclosure Inc.

In the 1996 cycle, 96 percent of Schering-Plough's $395,000 in corporate donations went to the GOP. So far this year, only about 60 percent of its $242,000 in soft money has gone to Republican party committees.

Charity donations -- Former surgeon general C. Everett Koop has backed Schering-Plough's position on the patent extension bill in letters and meetings over the past year. The company made a $1 million donation to Koop's personal foundation and advertises on his popular health care Internet site.

Corporate plane -- The company made its Gulfstream IV executive jet available to the exploratory presidential campaign of Sen. Orrin Hatch (R-Utah) starting in July, the same month Hatch agreed to hold a hearing on a bill that would set up a procedure where the company could argue for added patent life for Claritin.