Pharmaceutical giant Pfizer braced investors for little-to-no revenue growth in 2019 after its blockbuster erectile dysfunction drug Viagra, among others, lost patent protection and pain killer Lyrica faces similar competition from generic drugmakers this year.

Shares of Pfizer fell 2.7 percent in premarket trading Tuesday even after the drugmaker announced fourth-quarter earnings that exceeded Wall Street predictions. However, the stock was up more than 1 percent by midmorning trading amid the post-earnings conference call.

Here's how the company did compared with what Wall Street expected:

Earnings: 64 cents per share vs. 63 cents per share forecast by Refinitiv

Revenue: $13.97 billion vs. $13.89 billion forecast by Refinitiv

Pfizer's adjusted earnings of 64 cents per share for the quarter was 1 cent above Wall Street estimates and 2 cents higher than a year earlier. Revenue came in at $13.97 billion, higher than the projected $13.89 billion and the $13.7 billion it reported a year earlier.

Pfizer forecast its 2019 adjusted earnings to range between $2.82 to $2.92 a share, below average analysts' estimates of $3.04 a share. It sees revenue for 2019 at $52 billion to $54 billion, shy of estimates of $54.25 billion.

For the full year, Pfizer reported adjusted earnings $3 per share on revenue of $53.6 billion. It anticipates repurchasing about $9 billion of shares in 2019.

"We enter 2019 with confidence in the competitive positioning of our businesses, the prospects for our recently launched products and product line extensions, as well as the strength and breadth of our research pipeline," Pfizer CEO Albert Bourla said in a press release.

The earnings report marks Bourla's first since becoming CEO on Jan.1, succeeding Ian Read. The company announced plans to shuffle the company's senior management team in October and has been trying to bulk up its pipeline of drugs and therapies, especially in oncology, ahead of impending patent expirations.

Shares of Pfizer improved Tuesday after the company discussed on an earnings call its cancer drug portfolio and success with biosimilars.

Innovative health sales increased 8 percent, boosted by sales of blood thinner Eliquis and rheumatoid arthritis treatment Xeljanz. Sales in its essential health unit, which includes Viagra, fell 7 percent due in part to "pricing challenges" in the U.S. and generic competition, the company said. Viagra sales fell as Pfizer's blockbuster erectile dysfunction drug lost patent protection.

Pfizer's blockbuster drug Lyrica, which is expected to face generic competition later this year, brought in sales of $1.32 billion.

Shares of Pfizer have fallen more than 9 percent this year. The stock price has risen more than 1 percent during the past 12 months.