Yes, according to Testclear.com, Expedia does conduct a drug test on its employees.
As the site states, this drug test is only conducted on prospective employees, which means that once an employee has passed this stage, it is unlikely that they will have to undergo another test.
Why does Expedia need to drug test employees?
According to an advertisement for an Expedia sale agent, which was posted on LinkedIn, the drug screen test is combined with a background check in order to determine whether a candidate is eligible for the position.
The only way for an employee to be absolutely certain that Expedia will not conduct further drug tests on them in the future is to refer to their employment contract.
In the event that an employee is required to undergo further tests, either at random or not, this will be stipulated in no uncertain terms within the contract.
In most cases, you should be able to detox your body from any illicit substance within the first few months of employment, and it is unlikely that a second drug test would be required within that space of time.