In this Nov. 23, 2015, file photo, the Pfizer logo is displayed at world headquarters in New York. Pfizer Inc. (PFE) on Tuesday, July 31, 2018, reported second-quarter earnings of $3.87 billion. (AP Photo/Mark Lennihan, File)

Pfizer's second-quarter profit surged 26 percent, thanks to a 4 percent increase in medicine sales, higher income from partnerships and lower tax expenses.

The biggest U.S.-based drugmaker on Tuesday beat Wall Street expectations and boosted its 2018 profit forecast. However, Pfizer trimmed its sales forecast, warning that weakening currencies in Europe and Asia could nick revenue in coming quarters.

The maker of Viagra and advanced breast cancer drug Ibrance earned $3.87 billion, or 65 cents per share, up from $3.07 billion, or 51 cents per share, a year earlier. Earnings, adjusted for non-recurring events, were 81 cents per share, 6 cents better than industry analysts had expected.

New York-based Pfizer said revenue was $13.47 billion, up from $12.9 billion in 2017's second quarter. That topped analyst projections for $13.26 billion.

Chief Executive Ian Read said in a prepared statement that higher sales of Pfizer's key newer products was partly offset by more generic competition and lower sales of off-patent medicines, and by reduced production of some sterile injectable painkillers and other medicines at its Hospira unit. That slowdown while Pfizer upgrades a Kansas factory has been causing disruptive shortages in hospital supplies for the past year.

Sales were topped by Pfizer's Prevnar 13 vaccine against ear and other pneumococcal infections, up 8 percent at $1.25 billion, and by its Lyrica capsules for pain and fibromyalgia, though its sales dipped 3 percent to $1.22 billion. Sales of cancer medicines jumped 15 percent to $1.82 billion, led by Ibrance at $1.03 billion. Meanwhile, sales of Eliquis for preventing blood clots and stroke soared 47 percent to $889 million.

Pfizer said it now expects full-year earnings in the range of $2.95 to $3.05 per share, up from its May forecast for $2.90 to $3 per share. But the company lowered its revenue forecast a tad, to a range of $53 billion to $55 billion, down from its prior forecast for sales of $53.5 billion to $55.5 billion.

In premarket trading, Pfizer shares dipped 35 cents to $38.25.