GlaxoSmithKline Plc is recalling so-called starter kits of its Lamictal drug in the United States due to incorrect dosing, Europe’s largest drugmaker said on Friday.

The move is unlikely to have any significant financial impact but comes at an embarrassing time for the British-based group, which is facing a U.S. Food and Drug Administration (FDA) probe into manufacturing problems at a factory in Puerto Rico.

The 5-week blister packs of Lamictal are designed for patients initiating treatment with the drug, which is prescribed for epilepsy and bipolar disorder.

A spokesman said the move affected 39 batches, or around 100,000 individual kits, which were packaged by a third-party contractor. The drug is manufactured in North Carolina and England.

Lamictal is taken by around 150,000 U.S. patients with epilepsy and 100,000 with bipolar disorder. U.S. sales totalled $758 million in 2004.

The company said it had advised the FDA of the voluntary recall and would not produce any more starter kits until it had resolved the problem.