"The decision to dismiss him is consistent with how we would treat any other Penske Racing team member under similar circumstances," Roger Penske, team owner, announced in a news release Wednesday.
Allmendinger's No. 22 Dodge Charger will be driven by Sam Hornish Jr., who has been behind the wheel of the Sprint Cup car since Allmendinger was pulled just before the start of the July 7 Coca-Cola 400 at Daytona.
Penske said over the weekend at Indianapolis that he planned to meet with Allmendinger this week to discuss the decision.
"We've tried to keep his spirits up, but he realizes it's a serious situation," Penske said Saturday.
NASCAR doesn't release details of positive drug tests. Allmendinger said through a spokesman that he unknowingly took a banned substance after news of the positive test broke. He had his "B" sample tested with a toxicologist present, as permitted by NASCAR, but the same result was produced.
Allmendinger officially entered the NASCAR-sponsored recovery program last week, meeting with counselors Friday. He issued an apology Wednesday on his web site, thanking Penske Racing and the No. 22 team.
"I apologize for the distraction, embarrassment, and difficulties that my current suspension has provided," he said. "I have begun NASCAR's Road to Recovery program and look forward to using those resources and its completion to compete again in NASCAR in the near future.
Allmendinger is eligible to be under consideration for reinstatement only after completion of the recovery program.