The pharmacologic effects of some benzodiazepines may be increased by some beta-blockers. Propranolol and metoprolol may inhibit the hepatic metabolism of diazepam and other mechanisms may also be involved. Most changes have been clinically insignificant; however, increased reaction times and/or decreased kinetic visual acuity have been reported with some combinations. Observation for altered benzodiazepine effects is recommended if these drugs must be used together. Patients should be warned against driving or operating hazardous machinery.
per drugsdotcom interaction checker
Check with your doctor to be sure. Off hand, I can't see any reason why not, but better to be safe than sorry. Did the same doctor prescribe both medications? Is he/she aware that you have an RX for both?
If your doctor prescribed both of them the pharmacy would have cought it if it is not safe to take together. If your doctor did not prescribe both of them call your local pharmacy and ask them the question you asked us above, pharmacists know more about drug interactions then some doctors do. Or go to Walgreens, they have a "patient consultation" window. They answer all kind of questions about prescription drugs.
A few pharmacies have pharmacists that will note on your prescription to stop and talk with them. Most dont. They have become clearinghouses that are very impersonal in my opinion. Good thing my husband and I are aware of the meds we take because twice we have recieved the WRONG pills. At two different pharmacies! Yes, ask the pharmacist by all means, but don't depend on them to alert you.