Melatonin taken 30 minutes before bedtime has proven effective for many CH'ers. Effective dosages range, often success is reported at 9mg to 15mg, but test your body slowly and take it from there. Understand it may take 3 or 4 nights to titrate before you notive improvements. Start low, wait it out 3 or 4 nights, then increase dosages accordingly. Melatonin is not intended as a preventative replacement to your Lithium nor Verapamil; it is just an aid to hopefully assist reducing night time frequency and intensity.
O2 did not work for you? Were you using a NON-rebreather mask? One can be purchased here on this site, click on the left side of your screen (yellow tab titled CH store) and have a mask delivered to you next day. This mask will make a world of a difference with your aborts.
Were you using a high flow regulator with at least 25 lpm? If so, were you standing or sitting upright and hyperventilating the o2? Be honest with yourself! If you were not hyperventilating, it is a no wonder the o2 was not effective. I recommend trying it again! O2 is the least expensive, most effective and least harmful abortive treatment available for CH's. If you need assistance getting a high flow regulator, let us know and we will steer you in the right direction such as Flotec out of Indianapolis or Harbor Freight Tools for a welders regulator.
You mentioned Imitrex is your abort of choice, might as well get most bang for your buck, right? Are you familiar with the Imitrex tip? If not...see the left side of your screen (yellow tab) to understand how to get triple your dosage from just one syringe. if you have challenges understanding, PM me with your phone # and I will walk you through it on the phone.
Aggressive stimulants? Energy drinks containing the stimulants of Taurine/Caffeine slammed at onset of attack have proven helpful for many, especially when mixed with o2 as Joe mentioned; but limit your energy Taurine intake as you are taking Verapamil-which by the way 240mg is an extremely low dosage for CH's and you may consider increasing your dosage-do some research about Verpamil dosages on this site. Perhaps you are referring to the caffeine stimulant of a strong pot of bold Starbucks coffee such as French Roast or Sumatra blends? Maybe you are referring to other alternative treatment stimulants such as Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

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Whatever you choose to consider for your traditional or alternative treatments, always hit the search button and read the current threads and the archives to arm yourself with knowledge.
You are not alone! We understand your pains! Don't be a stranger!

-Gregg in Las Vegas