UPDATE 3-AcelRx Pharma shares sink as FDA rejects opioid painkiller

* Analysts had seen approval of drug likely

* AcelRx says requests made by FDA "manageable"

* Shares tumble as much as 62.6 pct to $2.00 (Adds analyst comment, details from conference call; Updates bullets, shares)

Oct 12 (Reuters) - Shares of AcelRx Pharmaceuticals Inc plunged more than 60 percent on Thursday after the U.S. Food and Drug Administration declined to approve its opioid painkiller Dsuvia.

There were more than 33,000 deaths in the United States in 2015 related to the abuse of the family of heavy-duty painkillers, and the resulting outcry has made the FDA extremely cautious about issuing new approvals.

The FDA last month rejected another opioid painkiller made by Intellipharmaceutics International Inc , asking for more proof of the drug's ability to prevent abuse.

AcelRx said the recommendations in the FDA's letter on Thursday were "manageable," and that it would resubmit the application for Dsuvia.

The regulator in its response letter to AcelRx had requested for additional safety data from the drug and for certain changes in the directions of use to ensure proper administration of the drug.

The change in instructions would be related to clearer communication to healthcare providers to properly administer the tablets, the company said on a conference call.

Analysts had been optimistic that Dsuvia would eventually be approved, citing its limited abuse potential as well as the regulator's decision to not hold an advisory committee meeting.

Dsuvia is a formulation of an opioid drug that is marketed for intravenous delivery, and is meant to be administered orally in patients using the company's proprietary delivery technology.

It would be used in medically supervised settings, such as emergency services and ambulatory surgical centers, an element which traditionally limits the potential for abuse.

The rejection was clearly disappointing and approval had been seen as likely, given the lack of a committee meeting, RBC Capital Markets analyst Randall Stanicky said in a client note.

AcelRx's other drug Zalviso, which had received a rejection from the FDA in 2014, is in a late-stage trial and the company expects to file for a marketing application by this year end.

Shares of the company plummeted as much as 62.6 percent to $2.00 in morning trading on Thursday. (Reporting by Manas Mishra in Bengaluru; Editing by Martina D'Couto)