Sigma Pharmaceuticals Ltd (ASX:SIP), which is selling its generic drugs unit to South Africa's Aspen Pharmacare, says revenues will be negatively affected by changes in government pricing of generic medicines.

The government recently finalised reforms to the PBS which will see the prices of generic medicines reduced. Given Sigma revenues are based on a mark up of drug prices, this will have a negative impact on revenues in the absence of improved product volumes, Sigma managing director and chief executive Mark Hooper said.

At its extraordinary general meeting in Melbourne today, Sigma told shareholders that it had gained a one-month extension and now has until March 2011 to repay some debt facilities totalling about $750 million.

The company chairman Brian Jamieson called on shareholders at the meeting to support the proposed sale of Sigma's pharmaceutical division to Aspen Pharmacare, which would result in gross proceeds of $900 million and allow Sigma to significantly reduce its outstanding debt position.

"Your directors unanimously recommend you vote in favour of approving the sale, and intend to vote their own shares in favour of the resolution," Mr Jamieson said.

"This will allow Sigma to fully repay its syndicated banking facility and significantly reduce the amount outstanding on its trade receivables securitisation."