This book written by one of the better headache doc in the U.S.
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MANAGEMENT OF HEADACHE AND HEADACHE MEDICATIONS, 2nd ed. Lawrence D. Robbins, M.D.; pub. by Springer. $50 at Amazon.Com.  It covers all types of headache and is primarily focused on medications. While the two chapters on CH total 42-pages, the actual relevant material is longer because of multiple references to material in chapters on migraine, reflecting the overlap in drugs used to treat. I'd suggest reading the chapters on migraine for three reasons: he makes references to CH & medications which are not in the index; there are "clinical pearls" about how to approach the treatment of headache; and, you gain better perspective on the nature of headache, in general, and the complexities of treatment (which need to be considered when we create expectations about what is possible). Finally, women will appreciate & benefit from his running information on hormones/menstrual cycles as they affect headache. Chapter on headache following head trauma, also. Obviously, I'm impressed with Robbins' work (even if the book needs the touch of a good editor!) (Somewhat longer review/content statement at 3/22/00, "Good book....")
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The Verap dose you mention is quite low by our usual usage. This protocol  is widely used in the U.S.

Headache. 2004 Nov;44(10):1013-8.   

Individualizing treatment with verapamil for cluster headache patients.

Blau JN, Engel HO.

    Background.-Verapamil is currently the best available prophylactic drug for patients experiencing cluster headaches (CHs). Published papers usually state 240 to 480 mg taken in three divided doses give good results, ranging from 50% to 80%; others mention higher doses-720, even 1200 mg per day. In clinical practice we found we needed to adapt dosage to individual's time of attacks, in particular giving higher doses before going to bed to suppress severe nocturnal episodes. A few only required 120 mg daily. We therefore evolved a scheme for steady and progressive drug increase until satisfactory control had been achieved. Objective.-To find the minimum dose of verapamil required to prevent episodic and chronic cluster headaches by supervising each individual and adjusting the dosage accordingly. Methods.-Consecutive patients with episodic or chronic CH (satisfying International Headache Society (IHS) criteria) were started on verapamil 40 mg in the morning, 80 mg early afternoon, and 80 mg before going to bed. Patients kept a diary of all attacks, recording times of onset, duration, and severity. They were advised, verbally and in writing, to add 40 mg verapamil on alternate days, depending on their attack timing: with nocturnal episodes the first increase was the evening dose and next the afternoon one; when attacks occurred on or soon after waking, we advised setting an alarm clock 2 hours before the usual waking time and then taking the medication. Patients were followed-up at weekly intervals until attacks were controlled. They were also reviewed when a cluster period had ended, and advised to continue on the same dose for a further 2 weeks before starting systematic reduction. Chronic cluster patients were reviewed as often as necessary. Results.-Seventy consecutive patients, 52 with episodic CH during cluster periods and 18 with chronic CH, were all treated with verapamil as above. Complete relief from headaches was obtained in 49 (94%) of 52 with episodic, and 10 (55%) of 18 with chronic CH; the majority needed 200 to 480 mg, but 9 in the episodic, and 3 in the chronic group, needed 520 to 960 mg for control. Ten, 2 in the episodic and 8 in the chronic group, with incomplete relief, required additional therapy-lithium, sumatriptan, or sodium valproate. One patient withdrew because verapamil made her too tired, another developed Stevens-Johnson syndrome, and the drug was withdrawn. Conclusions.-Providing the dosage for each individual is adequate, preventing CH with verapamil is highly effective, taken three (occasionally with higher doses, four) times a day. In the majority (94%) with episodic CH steady dose increase under supervision, totally suppressed attacks. However in the chronic variety only 55% were completely relieved, 69% men, but only 20% women. In both groups, for those with partial attack suppression, additional prophylactic drugs or acute treatment was necessary. (Headache 2004;44:1013-1018).
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HERE ARE TWO MAJOR DOCUMENTS WITH RECOMMENDED TREATMENTS FOR CLUSTER HEADACHE, ONE FROM A U.S. PHYSICIAN, THE SECOND FROM EUROPE.
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Here is a link to read and print and take to your doctor.  It describes preventive, transitional, abortive and surgical treatments for CH. Written by one of the better headache docs in the U.S.  (2002. Rozen)
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Treatment guidelines from Europe

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A. May, M. Leone, J. Áfra, M. Linde, P. S. Sándor, S. Evers, P. J. Goadsby:
EFNS guidelines on the treatment of cluster headache and other
trigeminalautonomic cephalalgias.
European Journal of Neurology. 2006; 13: 1066–1077.

Download free full text:
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(Thanks to "cluster" for link.)

A CH sufferer looking for a relief has to be one of the most motivated people on the planet. The reason this is such a lively forum is that CH relief can be such a maze. So you're lengthening your list of possible remedies and systematically trying them. I went over 20 years with no diagnosis (being female I didn't fit the profile) so I got inventive. One year ice packs on the back of my neck worked. Caffeine has worked. Cafergot has worked. The exercise thing -- an intense burst of cardiovascular -- has worked. Over time my CH "morphed." I began having kind of a rebound pattern after O2 use. I ended up getting prophylactic relief with verapamil at only a 160 mg daily dose. Keep checking in for support and ideas, and good luck! P.S. I did try the mushroom cure, to my kids' continuing amusement, but as if the anxiety attacks weren't enough, I had twice as many headaches the following 24 hours.

I used the cafergot along with my 02 as well. What flow rate did you use? If 7-8 lpm, get a regulator that goes to 25 lpm and try that.  Another pill you might try is Amerge. It is a long-lasting triptan and might help to take along with the 02. Good luck.