NEW YORK — Health care giant Johnson & Johnson said Tuesday it plans to buy drug delivery specialist Alza Corp. for $12.3 billion in stock, a deal that analysts said will make it easier for J&J to offer new ways for patients to take its drugs.

Alza, based in Mountain View, Calif., developed the technology for the best-selling Nicoderm nicotine patches sold by GlaxoSmithKline. It also makes time-released capsules that allow people to take fewer pills and systems that use electricity to push drugs through skin.

The purchase by Johnson & Johnson, the maker of Band-Aids and Tylenol that is based in New Brunswick, N.J., had been rumored for weeks.

The companies said in a statement Tuesday that their boards had approved the deal and hope to complete it in the July-September quarter. It is subject to approval by Alza shareholders and by regulators in the U.S. and Europe.

Ralph Larsen, Johnson & Johnson chairman and chief executive, said the deal was "an excellent strategic fit" for his company, strengthening several key pharmaceutical franchises, accelerating revenue growth and making important technology available to J&J.

Alza will retain its name and management as a free-standing J&J unit, said William C. Weldon, a vice chairman of Johnson & Johnson. He said Alza also would continue to develop new products based on its drug delivery technologies for its other pharmaceutical customers.

Ernest Mario, chairman and chief executive of Alza, said the deal will help Alza reach more patients worldwide.

Under terms of the transaction, J&J will swap 0.49 of its shares for each share of Alza. Based on J&J's closing price Monday, that would value Alza at $41.8362 a share. As part of the purchase, J&J will get $1.8 billion that Alza has in cash. J&J said the deal has a "net equity value" of $10.5 billion.

Alza stock rose $8.70, or 29 percent, to close at $38.75 Monday on the New York Stock Exchange amid reports a deal was imminent. J&J shares dropped $2.83, or 3 percent, to $85.38, also on the NYSE.

The deal is J&J's biggest ever, surpassing in value its 1999 purchase of biotechnology firm Centocor Corp. of Malvern, Pa., for $4.9 billion.

Alza's sales of its own drugs and its drug delivery work with drug makers will benefit from J&J's strong worldwide marketing presence. But analysts said some pharmaceutical companies might be reluctant to work with Alza on drug delivery methods in the future because the company would be owned by a direct competitor.

"Obviously that's a long-term issue," said Sandra Hollenhorst, an analyst with Prudential Securities Inc. "But if the drugs are currently marketed, it would be tough for them to switch to other drug delivery platforms."

J&J officials told analysts in a conference call that they are not concerned because they feel Alza has the best drug delivery technology to offer competing pharmaceutical companies.

Alza had been considered fair game since it called off a deal to be bought for $7.3 billion by North Chicago-based Abbott Laboratories, the nation's largest maker of medical diagnostic tests. The purchase was halted after the companies could not come to terms with antitrust concerns raised by the Federal Trade Commission.