I'm afraid the the complex of age, unclear Dx, and secondary Dx makes your question way outside of our league to handle.

In broad terms: Verapamil takes around2-3 weeks to kick in BUT the dosing may also have to be adjusted more than once to find the effective dose. So, the range of time can be rather wide.
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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).

hi Rosa

thanks for replying.  The pain is constant on both side all the time but  at a consistent level (4-7) the pain on the left side then comes and goes but is what she describes as intense stabbing or electric shocks which increase in frequency and intensity as the evening wears on.  It gets worse in the evening and early hours of the morning.

hope this clarifies things and thanks again for your interest.

Deb

Hi Rosa,
Thanks once again for replying. One theory because she's had nerve pain in the past is that the constant pain is caused by another condition. The pain at night/early morning my daughter describes as much worse and like a red rot poker going through her head or "the worst pain ever" and that she's "dying" which does seem to last around that time frame but can happen several times in a 24 hour period. No there's no drooping eyelid, she cn sweat a lot or get a runny nose but whether this is from all the crying and screaming.. She seems to find the pain's worse when she lies down and tends to rock violently, bang her head or hit herself. I think we've tried low dose steriods before with no effect but we'll definately try suggesting it again. The side effects of the verapamil is certainly very worrying especially with her POT syndrome - a condition causing very low blood pressure and her heart to work three times as hard as the normal heart when standing. I think that's the reason he's increasing it slowly and starting her on a low dose to get a balance with her other medication if it is the correct diagnosis does the verapmil have to be on a certain dosage for it to work maybe explaining why it's not been working yet? Thank you very much for the links - we'll certainly be asking our neuro a lot of questions when we next see him - and for taking your time to reply.
Deb

You're very welcome, rose

How big was the steroid dose you tried? I myself get complete remission of my Cluster Headache with doses of 40mg of Prednisolon per day. If my Cluster Headache -attacks would come mostly in the evening and during the night, I'd probably take the steroids a couple of hours before the evening or divide the daily dose in three equal amounts. Taking the steroids in the evening / just before going to sleep is the most harmful way of taking them considering the body's own steroid production, as the chemoreceptors in the body will then notice that there is already a big amount of steroids in the body, when there should be a low amount, and thus won't produce much more steroids in the morning. However, this will happen anyways when you use steroids on a long-term basis. A short-term trial of for example around two weeks shouldn't cause many side-effects or any kind of permanent drop in the steroids production to be worried about.

I can't say that I'm any kind of expert at POT-syndrome, but what you said sounds quite bad. Verapamil is a calcium-channel blocker which dilates the blood vessels and lowers the blood-pressure. You're saying that your daughter already has a constant very low blood pressure? I'd definitely be very careful about raising the daily dosage of Verapamil any further above the 240mg per day that you already have. For many who suffer from Cluster Headaches, a daily dose of 480mg of Verapamil is required to get help for the pain. Some require amounts as high as 1200mg per day. I myself have a normal pulse of around 60, but it dropped to 40 when I was using 480mg of Verapamil per day and thus had to stop taking it.

Fortunately, there are other drugs that you can try out for the headaches - topiramate and sodium valproate to name a few. Both of them have been used for Cluster Headaches and also some other types of headaches with relatively good success. They don't work for everyone, though. Something inexpensive what you could easily try would be to apply ice to the areas of her head which hurt during these nightly attacks. Cold acts to both suppress activity of the nerves which carry the pain-signals to the brain and also to constrict the blood vessels. I've used ice with somewhat good success myself against my Cluster Headaches - it needs to be applied so that the areas get really cold, though. I usually only have a thin plastic film between the ice and my skin.

High or low blood pressure, which POT-syndrome causes, is very often linked to chronic headaches. I think it definitely could be one factor in why your daughter has a chronic headache. However, like I said before, I don't have really any experience with POT-syndrome or knowledge of how to treat it. Does your daughter faint while standing up? I understand that's one of the defining characteristics of POTS.

I wish I could help you further. Hopefully your daughter gets some respite from the pain soon.

- Rosa

I think that 8 weeks on verap is a lot, esp if the dosage has gone up.

Lots of people state they typically use really high doses of verap for long times.

I can't stand being on the stuff at all. I can feel my body crumbling when I am on it - it is so hard to breathe.

I would get a second opinion if your doc wants to run the verap any longer, esp if it isn't working.

Hope brighter days are headed your way.....