"While this is a rare event, we are pleased that the (health department) shares our view that it is an important opportunity for the entire institution to explore any and all ways we can further improve medication safety," Langberg said.

The hospital has apologized to the patients' families and said it made changes to prevent a recurrence, including providing more training and requiring four pharmacy workers to verify a high-alert medication before putting it in a patient care unit.

The Quaid twins were at Cedars-Sinai for treatment of an infection. They were receiving intravenous medications, and the heparin was used to flush the catheters to prevent clotting.

Quaid and his wife, Kimberly, have sued Baxter Healthcare Corp., the Illinois-based makers of heparin, accusing the firm of negligence in packaging different doses of the product in similar vials with blue backgrounds.

A similar dosage error killed three premature infants at an Indianapolis hospital in 2006. Three others survived overdoses.

In February, Baxter Healthcare Corp. sent a letter warning health care workers to carefully read labels on the heparin packages to avoid a mix-up.