Andrx ( ADRX) said an employee made improper changes to its bookkeeping, causing it to overstate accounts receivable by $15 million since 1999.

Its shares were down 12% to $20.55 in the Instinet premarket session.

The drugmaker requested a five-day extension in which to file its second-quarter financial statement with the Securities and Exchange Commission. The matter turned up in an internal audit, Andrx said.

Specifically, the employee "altered certain accounting records pertaining to accounts receivable balances and aging relating to its pharmaceutical and distribution operations, thereby potentially affecting Andrx's allowance for doubtful accounts." The company's net accounts receivable of $103.6 million as of June 30, 2002 may have been overstated by as much as $15 million since 1999.

According to the company, the amounts that may have been overstated account for less than 1% of its $2 billion in net product sales during the period. Andrx said it is actively investigating the matter, but does not believe that the employee's actions will impact the company's business or financial condition in any substantial manner.