UPDATE 2-Cardinal Health forecasts fiscal 2018 profit below estimates

(Adds shares, forecast)

Aug 2 (Reuters) - Cardinal Health Inc forecast profit for fiscal year 2018 below analyst estimates as the drug distributor continues to struggle with declining generic drug prices, sending its shares down 5.6 percent in premarket trading.

Pharma supply chain, including pharmacy benefit managers and drug distributors, has been under pressure due to intense scrutiny over soaring drug prices.

Last week, Cardinal's rival McKesson Corp posted a much lower-than-expected quarterly profit, hurt by the lingering effects of a slowdown in the pace of price increases for branded drugs.

Cardinal said it expects its fiscal year 2018 profit forecast to be $4.85 to $5.10. Analysts on average had expected earnings of $5.27, according to Thomson Reuters I/B/E/S.

"While management had previously indicated that 2018 earnings would be down year-over-year, the midpoint of the guidance range came in $0.26 below our estimate," William Blair analysts wrote in a note.

The company, which had given a preliminary forecast for the fiscal year in April, said its "perspective and operating expectations have not meaningfully changed."

Cardinal said its pharmaceutical unit posted a 7 percent decline in profit in the fourth quarter ended June 30, largely due to low generic drug prices.

Net earnings attributable to the company fell to $274 million, or 86 cents per share, in the quarter, from $333 million, or $1.02 per share, a year earlier.

Excluding one-time items, Cardinal earned $1.31 per share, beating analysts' average estimate of $1.24.

Profit in Cardinal Health's medical unit rose 13 percent to $138 million in the reported quarter, reflecting robust demand for post-acute care products.

The company's medical business distributes medical, surgical and laboratory products to hospitals and other healthcare providers.

Cardinal Health, which also makes surgical apparel and gloves, said in April it would bolster its growing medical products business through a $6.1 billion deal for Medtronic Plc's medical supplies units.

Net sales rose 5 percent to $32.97 billion. (Reporting by Akankshita Mukhopadhyay and Manas Mishra in Bengaluru; Writing by Ankur Banerjee; Editing by Sai Sachin Ravikumar and Shounak Dasgupta)