(Reuters) - Drugmaker Medivation Inc returned to recording a quarterly loss after a rare first-quarter profit as expenses rose, sending its shares down 3 percent after market.

April-June net loss narrowed to $5.5 million, or 15 cents per share, from $9.5 million, or 27 cents per share, a year earlier.

Revenue, which Medivation generates mostly through collaborations with Astellas Pharma Inc, more than doubled to $42.9 million, boosted by $35.6 million of deferred revenue from ending a drug development deal with Pfizer Inc.

Pfizer and Medivation stopped developing a potential Alzheimer's drug in January after it failed to show efficacy in a late-stage study.

Medivation's operating expenses rose 67 percent to $43.9 million for the second quarter.

The company said it expects to recognize the remaining $5.5 million of deferred revenue from ending its deal with Pfizer in the third quarter.

Medivation's shares closed at $98.42 on the Nasdaq on Thursday. They fell to $95.50 in extended trading.

(Reporting by Zeba Siddiqui in Bangalore; Editing by Joyjeet Das)