Otsuka Holdings Co. agreed to buy California-based Avanir Pharmaceuticals Inc. for about $3.54 billion, a deal that gives the Japanese company new treatments for neurological conditions.

Tokyo-based Otsuka will pay $17 a share, it said in a stock exchange statement today. That’s 13 percent higher than Avanir’s closing price of $15 yesterday.

The deal will give the Japanese drugmaker access to Avanir’s pipeline of treatments for Alzheimer’s, Parkinson’s and migraines. Otsuka has been looking for new sources of growth before 2015, when it faces patent expiration on Abilify, one of the world’s best-selling treatments for schizophrenia.

Avanir’s Nuedexta is approved to treat pseudobulbar affect (PBA), or uncontrollable crying or laughing believed to be caused by neurologic conditions such as Alzheimer’s, Parkinson’s and multiple sclerosis. Its AVP-786 treatment intended for agitation associated with Alzheimer’s disease is being prepared for late-stage clinical trials.

’The two products Avanir has are unique, exciting and fit with Otsuka,’’ said Yasuhiro Nakazawa, a health-care analyst at SMBC Nikko Securities said via phone. ’’They will help Otsuka have sustainable growth after Abilify.’’

Otsuka is entering into the deal after Avanir’s share price has more than quadrupled this year. The U.S. company’s shares surged 85 percent on Sept. 15 after it reported positive results from a study.

Otsuka also makes Pocari Sweat drinks and Soyjoy nutrition bars. It gets about about 41 percent of its revenue from North America, data compiled by Bloomberg show. Its shares closed 2.1 percent higher at 3,864.5 yen in Tokyo trading today.

Nuedexta makes up almost all of Avanir’s revenue, and it brought in sales of $94 million in the twelve-months through June 2014, a 50 percent increase from a year earlier.

The deal is expected to close in the first quarter of 2015.

The purchase brings the total value of outbound acquisitions from Japan this year to $50.9 billion, according to data compiled by Bloomberg. Japanese companies announced $43.8 billion of outbound acquisitions during the same period in 2013, the data show.