Sri Lanka had gone for quick runs en route to amassing their huge total and their 107-run lead but the wicket had not deteriorated enough for their bowlers to be effective.
Fast bowler Lahiru Kumara has been ruled out of the series with a hamstring injury and Karunaratne confirmed Sri Lanka have recalled left-arm wrist spinner Lakshan Sandakan and seamer Chamika Karunaratne as replacements for the second test that will be also played in Kandy starting on April 29.
Man of the match Karunaratne was pleased with his effort despite the team failing to secure victory.
"When you play a test you have to be mentally prepared to be on the field all five days, whether that's fielding or batting. Yes, you can feel it in your body when you've been fielding a couple of days, but when you get a chance to bat, you've got to take that opportunity," he said.
"Even in the West Indies I got a start a couple of times but couldn't make a big score. So once I got a start and got set here, I really wanted to bat long, especially as they'd already made a big score."
His Bangladesh counterpart Mominul Haque said the draw was a fair result and was relieved that his team had bounced back after enduring a string of poor performances.
"It was a very good batting wicket where the bowlers had very little help. So I think it is best to accept a draw. Our bowlers tried really hard. Tamim set up our tone with his 90. It was an important innings."
Mominul also recorded his first overseas hundred in a Test during the match.