I could find only two citations using Flun; one case where it benefitted a seizure disorder in a patient with Cluster and this one;

Wien Med Wochenschr. 1993;143(19-20):514-8.
[Calcium channel blockers in therapy of neurologic diseases].
[Article in German]
Wessely P, Wöber-Bingöl C.
SourceUniversitätsklinik für Neurologie, Wien.

Abstract
The clinical use of calcium antagonists (Ca-antagonists) in neurological diseases focuses on 2 main therapeutic fields: (a) For the therapy of migraine flunarizine is the first choice therapy and nimodipine is a second line treatment.

WITH VERAPAMIL CLUSTER HEADACHE CAN BE TREATED SUCCESSFULLY, FLUNARIZINE SHOWS LESS IMPRESSIVE CLINICAL EFFICACY.

The therapy with flunarizine may be restricted due to the incidence of extrapyramidal disturbances and depressions as known side effects. (b) The therapy of clinical conditions after subarachnoidal bleeding with nimodipine is well established. In the therapy of acute cerebral ischemia the therapeutic efficacy of nimodipine administered orally is not therapeutically proved until now; the intravenous administration of nimodipine offers the risk of acute hypotensive reactions. At present the usefulness of the administration of ca-antagonists in the so-called cerebrovascular insufficiency or dementia and various others cerebral disorders with vertigo could not be demonstrated.

PMID:8135034[PubMed]

In case you have to "sell" your doc:

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).

=======================================
SLOW-RELEASE VERAPAMIL

Dr. Sheftell applauded the protocol for verapamil used by Dr. Goadsby and colleagues, which entailed use of short-acting verapamil in increments of 80 mg. “This method was suggested by Lee Kudrow, MD, 20 years ago as an alternative to slow-release verapamil,” Dr. Sheftell noted.

“I would agree with using short-acting verapamil, rather than the sustained-release formulation, in cluster headache,” he said. “I prefer the short-acting formulation with regard to ability to titrate more accurately and safely. My clinical experience anecdotally demonstrates improved responses when patients are switched from sustained-release verapamil to short-acting verapamil.”

Dr. Goadsby agreed that his clinical experience was similar. “There are no well-controlled, placebo-controlled, dose-ranging studies to direct treatment. This is one of those areas where clinicians who treat cluster headache have to combine what modicum of evidence is available with their own clinical experience,” Dr. Sheftell commented.
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Not a reason to avoid Verap--but to be aware.

J Headache Pain. 2011 Apr;12(2):173-6. Epub 2011 Jan 22.
Cardiac safety in cluster headache patients using the very high dose of verapamil (=720 mg/day).
Lanteri-Minet M, Silhol F, Piano V, Donnet A.
SourceDépartement d'Evaluation et traitement de la Douleur Médecine palliative, Pôle Neurosciences Cliniques du CHU de Nice, Hôpital Pasteur Avenue de la Voie Romaine, 06002 Nice Cedex, France. lanteri-minet.m@chu-nice.fr

Abstract
Use of high doses of verapamil in preventive treatment of cluster headache (CH) is limited by cardiac toxicity. We systematically assess the cardiac safety of the very high dose of verapamil (verapamil VHD) in CH patients. Our work was a study performed in two French headache centers (Marseilles-Nice) from 12/2005 to 12/2008. CH patients treated with verapamil VHD (=720 mg) were considered with a systematic electrocardiogram (EKG) monitoring. Among 200 CH patients, 29 (14.8%) used verapamil VHD (877±227 mg/day). Incidence of EKG changes was 38% (11/29). Seven (24%) patients presented bradycardia considered as nonserious adverse event (NSAE) and four (14%) patients presented arrhythmia (heart block) considered as serious adverse event (SAE). Patients with EKG changes (1,003±295 mg/day) were taking higher doses than those without EKG changes (800±143 mg/day), but doses were similar in patients with SAE (990±316 mg/day) and those with NSAE (1,011±309 mg/day). Around three-quarters (8/11) of patients presented a delayed-onset cardiac adverse event (delay =2 years). Our work confirms the need for systematic EKG monitoring in CH patients treated with verapamil. Such cardiac safety assessment must be continued even for patients using VHD without any adverse event for a long time.

© The Author(s) 2011. This article is published with open access at Springerlink.com

PMID:21258839[PubMed]

My doc believed flunarizine tablets would help alot more than verapamil since it acts more centrally whereas verapamil is more peripheral. Know more here internationaldrugmart.com/flunarizine.shtml