NEW YORK (CNN) - Pfizer Inc. Wednesday launched a plan to enable 43 million uninsured Americans, regardless of age or income, to get the company's medications free or at "significant savings."

Separately, the nation's biggest drugmaker said Chinese officials have overturned Pfizer's patent for Viagra, adding it would appeal the decision. Its patent would remain in effect until the issue is resolved, Pfizer said, according to news wire reports.

New York-based Pfizer (PFE: up $0.01 to $33.88, Research, Estimates) sells medicines to treat high blood pressure, heart disease, depression, diabetes and other conditions.

It makes 11 of the top-selling drugs in the United States, including Lipitor, a cholesterol-lowering medication, the anti-depressant Zoloft, Zyrtec allergy pills, and Viagra for impotence, according to NDCHealth, a health care services company.

"We are providing choice, simplicity and expanded access to help Americans get the medicines they need," Pfizer CEO Hank McKinnell said in a statement.

Industry analysts said part of Pfizer's motivation could be an attempt to stem the tide of Americans going to Canada to get medications at discounted prices.

People can enroll in the plan starting in August when Pfizer will launch a Web site and toll-free number, the company said.

Here are key elements of the plan, according to New York-based Pfizer:

• Families making less than $45,000 a year (under $31,000 for individuals) will receive average savings of 37 percent, and up to 50 percent off the average cash price at retail pharmacies for most Pfizer medicines
• Families making more than $45,000 a year (and $31,000 for individuals) will receive an average savings of 15 percent, and up to 25 percent off the average cash price at retail pharmacies for most Pfizer medicines
• Families making less than $31,000 per year (less than $19,000 for individuals) can receive free Pfizer medicines from their physicians' offices

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• Families making less than $31,000 (less than $19,000 for individuals) can receive free Pfizer medicines from eligible federally qualified community health centers and hospitals
• Low-income Medicare beneficiaries on all Medicare-approved drug discount cards will have access to many Pfizer medicines for a flat fee of $15 per prescription after they have exhausted a $600 credit.

Pfizer said its initiative is supported by a number of officials including Health and Human Services Secretary Tommy Thompson and Sen. Hillary Rodham Clinton, D-N.Y.

"Pfizer is helping those in dire need get the medicine they often require," Pfizer quoted Clinton as saying. "This effort holds the promise of helping people in real need, and that is vitally important."