Shire Pharmaceuticals of the UK says that Teva Pharmaceuticals has notified it that it is challenging additional doses of the former’s top-selling attention deficit hyperactivity disorder drug, Adderall XR (extended-release amphetamine salts). The Israeli company, which had already challenged the patent covering the 10mg and 30mg doses of the drug, has now also filed for US approval of the 5mg, 15mg and 20mg dosages.

Shire says it remains committed to protecting the patents covering Adderall XR, which it notes are due to expire in 2018. The firm already has lawsuits pending against Barr Laboratories and Impax Laboratories, which were the first two companies to notify Shire that they had filed for approval of generic versions of the drug [[08/12/04e]], [[14/01/05c]]. The UK firm is currently reviewing the details of Teva’s latest notification, after having decided against suing the latter company for its application to market copycat versions of the 10mg and 30mg doses of the drug [[12/04/05d]], [[23/02/05b]].

None of the firms can launch their respective generic versions of the product without winning US Food and Drug Administration clearance, Shire notes. Barr, which has “first to file” status and could also be entitles to 180 days of market exclusivity [[10/01/03b]], must also wait for the expiration of the 30-month stays launched after Shire filed suit against the firm, or a court ruling in its favour.