Which is incorrect regarding the pharmacological treatment of migraine?

• A. chlorpromazine is a first line agent
• B. sumotriptan is a first line agent
• C. dihydroergotamine should not be given if sumotriptan has already been taken
• D. pethidine is not as effective in treatment and has a higher rebound c.f other agents
• E. dexamethasone has been proven to decrease rate of recurrence