Rehman, who tested positive while playing for Somerset in the English county season, had already been withdrawn from the Sialkot Stallions squad due to play in the Champions League Twenty20 qualifying tournament in South Africa starting on October 9.
On Wednesday it was confirmed that the drug in question was cannabis. The 12-week punishment meted out by the England and Wales Cricket Board will finish on December 21.
"Somerset County Cricket Club fully supports the action taken by the ECB," Somerset chief executive Guy Lavender said.
"The club does not condone the use of illegal drugs in any circumstances and all Somerset players are made fully aware of this policy on a regular basis."
Rehman, who initially claimed that he had not taken anything, backtracked in an apology for using the drug.
"I apologise to my family, the PCB, the ECB, Somerset County Cricket Club, my team-mates and my fans," Rehman said.
"It was an error of judgement on my part that will cost me dearly and I would like it to be a lesson to all others in sports elsewhere.
"I will do my best to stay fit and focused during my suspension, and God-willing, will be available for selection for the India series should the PCB see it fit for me to be selected."
Pakistan are to tour India in a short series in December-January 2013 with Chennai, Calcutta and Delhi hosting one-day internationals and T20 fixtures in Bangalore and Ahmedabad.
The 32-year-old Rehman, who has played 17 Tests and 25 one-day internationals, had a successful season for Somerset before returning home.
- Somerset County Cricket Club