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Shares of Apricus tank after FDA declines to OK erectile dysfunction cream

* Vitaros first rejected a decade ago

* FDA flags safety concerns with ingredient, manufacturing

* Drug already approved in several other countries

* Analyst estimated peak sales of $200 mln

* Co set to lose 76 pct of market value (Adds background on drug, analyst comment, updates share price)

By Tamara Mathias

Feb 16 (Reuters) - The U.S. Food and Drug Administration on Friday declined to approve Apricus Biosciences Inc's Vitaros, a cream to treat erectile dysfunction, for the second time in a decade, sending the company's shares down more than 70 percent before the opening bell.

The drugmaker was hoping to sell Vitaros, possibly through commercial partner Allergan Plc, to patients unable to use oral medications and also looking for less invasive existing options.

Apricus is set to lose about 74 percent of its market value, which stood at nearly $49 million as of Thursday's close.

Male impotence is currently treated with pills taken orally, such as Pfizer's Viagra, which has raked in blockbuster sales but is associated with side effects like headaches, blurred vision and dizziness.

Existing drugs are also considered risky for men with diabetes or cardiovascular disease.

Alprostadil, the active ingredient in Vitaros, belongs to a class of medicines that work by dilating blood vessels and is presently only available in the U.S. as an injection or a suppository that must be inserted into the urethra.

Vitaros is applied to the skin with a disposable applicator.

About 20 million men in the United States suffer from erectile dysfunction, which could be caused by physical conditions such as obesity or injury, or be psychological.

The FDA flagged certain safety concerns related to an ingredient in Vitaros and identified deficiencies in its chemistry and manufacturing, the company said.

The ingredient, DDAIP.HCl, helps in the absorption of skin products and is a core part of Apricus' proprietary drug delivery technology.

Analysts said the rejection 10 years ago was partly due to concerns bought by the FDA that the treatment could cause cancer in patients or their sexual partners.

"Back in 2008, drug applications that involved substances which could conceivably cause cancer were treated like nuclear waste by the FDA," H.C. Wainwright analyst Raghuram Selvaraju, who had expected an approval, told Reuters ahead of the decision.

Selvaraju estimated that Vitaros could take in $200 million four or five years after its launch.

Outside of the U.S., Vitaros has been on the market for several years and is sold in Canada, Mexico, parts of the Middle East and much of Europe by the company's commercial partner, privately held Ferring International Center S.A.

Chief Executive Officer Richard Pascoe said the company will provide an update in early March on its plans for the drug. (Reporting by Tamara Mathias in Bengaluru; Editing by Savio D'Souza, Bernard Orr)