Pfizer (PFE -0.19%) today announced the completion of its acquisition of privately held NextWave Pharmaceuticals, which focuses its drug research and development efforts on products designed to treat attention deficit hyperactivity disorder (ADHD).

After closing the acquisition, Pfizer now holds the exclusive North American rights to distribute Quillivant XR, the first once-daily liquid medication approved by the FDA to treat ADHD. According to Pfizer's press release, Quillivant XR is expected to be available in pharmacies in January, after receiving FDA approval in September.

Pfizer announced its intention to acquire NextWave Pharma in October, saying it would pay $255 million to NextWave's shareholders at the closing of the transaction and up to $425 million if certain sales milestones are reached. Pfizer made a $20 million option payment to NextWave in the second quarter of this year.