The Clueless star died on 20 December (09) after suffering a cardiac arrest at the Hollywood Hills home she shared with husband Simon Monjack. She was 32.
A coroner's report released on Thursday (04Feb10) lists the primary cause of death as community acquired pneumonia, with contributing factors of iron deficiency anaemia and "multiple drug intoxication". Her death was ruled accidental.
Coroners officials confirmed prescription medications also played a role in her death.
Further details about the types of drugs found in her system will be released in several weeks, when toxicology reports are completed.
Murphy's widower Monjack and his mother-in-law, Sharon, have repeatedly denied allegations the actress abused prescription drugs and suffered from an eating disorder.
The pair maintained Murphy had suffered flu-like symptoms days before her death.