On Thursday it was ruled that the Clueless star – who tragically passed away in her Hollywood Hills home on December 20 – died as a result of the lung condition, and that iron-deficiency anaemia and "multiple drug intoxication" were secondary factors.
It was also noted that all the drugs were prescription medicines.
Simon Monjack, who wed the 32-year-old actress in May 2007, and Brittany's mother Sharon Murphy had both said they believed her death to be the result of a congenital heart murmur.
The English director has also said that while Brittany had been showing flu-like symptoms on the day of her death, his wife had not seemed to be very ill.
"She wasn't coughing up," he told People. "I've had pneumonia and coughed up handfuls of spittle. So yeah, everything surprised us, everything."
He also said he could not comment on the fact the coroner said Brittany's death – officially ruled as accidental - could have been prevented.
But earlier Assistant Chief Ed Winter confirmed to the US publication: "Murphy was planning on seeing a doctor but unfortunately passed away before she did,"
"This was a case of a person who was anaemic who was taking medication when she should've been getting medical treatment."
A complete report is expected to be released in two weeks time.