LONDON - Pfizer Inc. was turned down twice by fellow drugmaker AstraZeneca PLC, but the maker of Viagra and Lipitor said Monday that its proposed $100 billion acquisition makes sense for shareholders of both companies, and it's considering its next steps.

A tie-up would bring new and complementary products to Pfizer, executives said on a conference call, important as patents on profitable medicines expire. Pressure on Pfizer for a deal also may be coming from a desire to save big money on taxes on the piles of cash it earned and keeps overseas.

During conference calls with investors and journalists, Pfizer executives said a combination would also bring major savings - meaning job and other cost cuts.

Pfizer, the world's second-biggest drugmaker by revenue, said acquiring No. 8 AstraZeneca would strengthen research programs and potentially produce drugs sooner in Pfizer's priority areas, particularly cancer, heart disease, pain and immune disorders. That could eventually benefit patients.

Pfizer executives said AstraZeneca management rejected an initial bid in January, but Pfizer renewed its offer Saturday due to "recent market developments" - the spate of news about other potential deals last week.

What's driving merger mania?

The run of big deals among drugmakers is driven by the increasing financial pressures on the lucrative pharmaceutical industry: continuing patent expirations that slash billions in annual revenue, lack of enough new drugs to make up for that, and government and private insurers squeezing drugmakers for lower prices.

"This transaction, I believe, will make us a stronger company and will give us greater cash flow and more ability to invest," Pfizer CEO Ian Read told journalists.

Last week, Swiss drugmaker Novartis AG, the top drugmaker, agreed to swap its vaccine business for GlaxoSmithKline PLC's cancer drug unit and sell its veterinary drug unit to Eli Lilly and Co. Meanwhile, Canada's Valeant Pharmaceuticals and activist investor Bill Ackman made a cash-and-stock offer worth about $45.6 billion for Botox and eye drug maker Allergan Inc.

A taxing question

Some analysts say the main impetus is limiting a potential tax hit on Pfizer, best known for Viagra, pain medicine Celebrex and Lyrica, and immune disorder drug Enbrel.

Like many U.S.-based global companies, Pfizer has a small fortune in cash profit earned and held overseas. Bringing it back home would mean Pfizer would have to pay taxes on it at relatively high U.S. rates.

Jefferies LLC analyst Jeffrey Holford estimates Pfizer has roughly $30 billion held abroad, and writes that the "main drivers" behind the proposal are the tax benefits and the chance to use that cash.

Such cross-Atlantic deals have become fashionable. In 2012, Johnson & Johnson used profits from an Irish subsidiary to buy orthopedics product maker Synthes for nearly $20 billion.

Where are you domiciled?

Pfizer proposes using some of that money overseas, along with shares of its stock, to pay for AstraZeneca, maker of cholesterol drug Crestor and asthma treatment Symbicort. Pfizer also wants to combine the two drugmakers under a new holding company incorporated in the United Kingdom, although it would keep its headquarters in New York and remain listed on the New York Stock Exchange.

Incorporating overseas through acquisition has been done by other drugmakers, notably to save on taxes. For example, both Actavis plc and Perrigo Inc. have acquired Irish companies and then "redomiciled" in Ireland.

The details

Pfizer's proposal would represent a 30 percent premium on AstraZeneca's closing share price of 35.26 pounds on Jan. 3, around when the first offer was made. AstraZeneca said that "very significantly undervalued AstraZeneca and its prospects."

Pfizer's bid for AstraZeneca would mark the biggest-ever foreign takeover of a British business. The Conservative-led government of David Cameron may take a position on the matter, as it's interested in bolstering the country's biotech sectors.

AstraZeneca is currently undergoing a major research and development reorganization to offset the expiration on patents for blockbusters such as Crestor. The company has been reducing costs and trying to make research programs more productive.

Pfizer's done three huge acquisitions since 2000 and just reorganized its operations into three business groups, after divesting some non-core operations.

Read said it continues to plan to eventually break off parts of the company.