New York - The effect of expiring patents pushed Pfizer earnings lower Monday, as the pharmaceutical giant reiterated its interest in acquiring British company AstraZeneca.

Earnings for the first quarter fell 15.3 percent to $2.3 billion as a number of high-profile patent expirations hit sales.

Pfizer said it hoped its increased bid for AstraZeneca “will provide the basis for AstraZeneca to engage with Pfizer and enter into discussions relating to a possible combination of the two companies.”

AstraZeneca Friday rejected Pfizer's $106 billion takeover, saying the terms of the offer, up from a previous bid of $99

billion, “substantially undervalue AstraZeneca and are not a basis on which to engage with Pfizer.”

Options for Pfizer in its pursuit of AstraZeneca include raising the bid again, undertaking a hostile takeover campaign aimed at shareholders or dropping the idea.

Pfizer's earnings translated to $2.3 billion on $11.4 billion in revenues, down from $2.8 billion on $12.4 billion on revenues.

The results translated into 57 cents per share, two cents better than expectations. Revenues lagged analyst forecasts for $12.1