Johnson & Johnson, fighting to preserve its reputation in the wake of the poisoning of capsules of its best-selling pain killer Tylenol, said yesterday that it plans to change the packaging of its product to make it harder to tamper with it before putting it back on the market.

The company has asked retailers across the country to pull all packages of Tylenol capsules off the shelves, even though only the extra-strength brand was involved in the poisoning. Tylenol tablets have remained on sale, however; pills are far more difficult to tamper with than capsules.

The move is part of an industry effort to make packages safer after seven people in the Chicago area died when they took Tylenol capsules that apparently had poisons placed in them after they reached drug store shelves.

A joint Federal Drug Administration-industry committee will meet here today to look into the technical problems of putting all medicines sold over the counter in tamper-resistant packages.

As an indication of the seriousness of the drug industry's efforts to redo its containers, the stock of West Co., a little-known Pennsylvania firm that specializes in medical packaging, jumped $3.50 Tuesday, the highest percentage increase of any company listed on the New York Stock Exchange.

Johnson & Johnson officials declined to say what kind of new packaging they would put Tylenol in or when the product -- which had captured a 37 percent share of America's billion-dollar-a-year pain reliever market since its introduction in 1975 -- would return to the shelves. The only time frame given for the new packaging was "soon," which some industry analysts said could be months away.

The company also is working to rebuild consumer confidence in a wide range of its products. Although its stock had fallen more than $7 since last Wednesday, it rose yesterday by $2.50 on the NYSE.

David Collins, chairman of McNeil Consumer Products, the Johnson & Johnson subsidiary that makes Tylenol, predicted that the poisoned capsules will not mean the end of the product.

But some industry analysts predicted that the name Tylenol has been tainted by the deaths, and suggested that Johnson & Johnson might be forced to change it before putting it back on the market.

If so, that would cost the company its hard-won edge secured by strong advertising campaigns and would give a boost to its rivals in the highly competitive pain-reliever market.

There were some indications, though, of a consumer resistance to any packaged drug product, according to a nationwide survey by Leo Shapiro Associates of Chicago, which monitors buying trends. George Rosenbaum, the company president, said one sign of the survey is that people are becoming wary of purchasing other packaged products