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Penn had a part in the movie True Romance
Actor Chris Penn died from the effects of a mix of medications and an enlarged heart, a Los Angeles coroner has ruled.
"There is absolutely no indication that this is anything but an accident," said county coroner spokesman Craig Harvey.
Penn's body was discovered by a housekeeper at his home in Santa Monica, Los Angeles, on 24 January.
The actor, who was 40 when he died, starred in films such as Reservoir Dogs, Rush Hour and Starsky and Hutch. He was the brother of Sean Penn.
The main cause of death was "non-specific cardiomyopathy" - an enlarged heart - which had been affected by "multiple medication intake".
"We know he had several prescriptions, including promethazine with codeine, which featured predominantly in his death," said Mr Harvey.
Promethazine is an antihistamine and codeine is a painkiller which can also be used to treat severe coughs.
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Star family: Sean Penn, Eileen Ryan, Chris and Michael Penn
"We don't know how much he ingested or when. There are a lot of 'what ifs' to be factored in," said Mr Harvey.
Penn's heart weighed 700 grams, a few hundred grams heavier than the average heart.
He was not taking any heart medication at the time of his death, said Harvey.
A full coroner's report with more details will be available within the next few weeks.
Penn's latest movie, The Darwin Awards, was shown at the Sundance festival a few days after his death.
He played a hunter who fakes the theft of his truck to collect insurance money in the comedy adventure, which also stars Winona Ryder, Joseph Fiennes and David Arquette.
