The AFL confirmed the penalty on Friday after investigations by both Carlton and the league into what it described as Cowan's use of an illicit substance last weekend. As well as the two-match ban at the start of next season, Cowan was issued a $5000 suspended fine and now has an adverse finding listed against his name under the AFL's illicit drugs policy.
In a statement released by Carlton shortly after the penalty was announced, Cowan apologised for his actions.
"I should never have put myself in such a vulnerable situation, I want to apologise for the impact my actions have had on my family and the football club," he said.
"I also want to thank the medical professionals who helped me on the night, the football club for their ongoing support and everyone who took the time to reach out and make sure I was OK. This is a wake-up call and I am just so grateful to now be in a position to learn from this."
The league's chief operating officer, Tom Harley, said in confirming the penalty that AFL players were expected to meet community standards.
"AFL players have a responsibility to themselves and their professional careers to uphold community expectations. They are well-educated when it comes to the harms associated with the use of illicit substances. Lachlan admitted his mistake and understands he must be accountable for his actions," Harley said.
The AFL said it considered "the circumstances in which the matter subsequently became public" when reaching its decision. Cowan will also be required to undertake additional education on illicit substances and their effects, beyond the mandatory training all AFL players complete.