Shares in Abraxis BioScience Inc. hit the bottom of a rollercoaster ride, dropping nearly 13 percent Friday after gaining 24 percent earlier in the week.

The Los Angeles-based biotech firm announced that it had won U.S. approval to market the first copy of AstraZeneca’s injectable antibiotic Cefotan, an antibiotic used in hysterectomies and cesarean sections. It is also recommended for colorectal surgery. Abraxis said it plans to launch the drug this month.

Abraxis said that its Abraxis Pharmaceutical Products division is the only supplier of the drug which was pulled from the market in 2006 over issues stemming from the sourcing for raw materials. Abraxis said it secured a new raw material supplier.

Shares in Abraxis had gained earlier in the week after the company reported strong second quarter earnings a day after receiving approval from the FDA for larger doses of its oxytocin drug, which is used to help with contractions during the delivery of babies as well as to control postpartum bleeding.

Sharers in Abraxis were down $3.06, or 13 percent, to $21.10 in afternoon trading Friday on the Nasdaq.