Abbott Laboratories reported better-than-expected quarterly sales and earnings, fueled by strong demand for its Humira arthritis drug and its wide array of prescription medicines, nutritional products and medical devices.

The company earned $1.24 billion, or 78 cents per share, in the first quarter, up from $864 million, or 55 cents per share, in the year-earlier period.

Excluding special items, Abbott earned $1.03 per share. Analysts, on average, had forecast $1.00.

Revenue rose 4.6% to $9.46 billion, topping Wall Street expectations of $9.36 billion.

Global sales of Humira, by far the company's biggest product, surged 17% to $1.93 billion, putting it on track to leapfrog cholesterol fighter Lipitor and become the world's top-selling medicine.

Sales of nutritional products rose 10% to $1.6 billion, helped by new product launches and growing demand in emerging markets. The company's diagnostics products also reported solid growth.

Sales of vascular products, comprised largely of heart stents, fell 5% to $803 million on declining revenue from Boston Scientific's Promus stent. Promus is a private-label version of Abbott's widely used Xience stent; Abbott has shared in profits from Promus under a longstanding agreement to manufacture the product for Boston Scientific.

Abbott in October announced plans to spin off its branded prescription drug business into a separate publicly traded company amid criticism that it has become too dependent on Humira. The injected drug is facing growing competitive threats, including possible cheaper generic versions and a pill being developed by Pfizer, and concerns about its vulnerability have held back Abbott shares.