OPIOIDS AND PHENOBARBITAL - OPIOIDS, GENERAL

The concurrent use of opioids (including weak opioids such as codeine) and barbiturates appears to increase sedation and respiratory depression. Although phenobarbital decreased the analgesic effects of pethidine (meperidine) in one study increased sedation has been reported with the combination.
Concurrent use need not be avoided, but be aware of the potential for respiratory depression, especially in patients with a restricted respiratory capacity.