If you're going to jab yourself through your pant leg, I suggest you get the auto-inject pens (as opposed to regular syringes). The needles are a little beefier (and as a result, they hurt more).

I've told people that if a regular syringe feels like getting stuck with a thumbtack, an auto-inject pen feels like a 6-penny nail.

Batch's solution above is the best. Jabs only as a last resort, and then I'd try to make it to the restroom to do it straight into the skin, cleansed with an alcohol wipe first.

If you have time before the travel begins, ask your doc to run a trial with this med to see if it's effective for you. I found it almost as fast acting as Imitrex but with the convenience of it being a pill.

(Also get your doc to write a letter giving your diagnosis and listsing the meds you will be carrying  with you. That should satisfy security/customs.)
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Headache 2001 Sep;41(8):813-6 

Olanzapine as an Abortive Agent for Cluster Headache.


Rozen TD.
Department of Neurology, Jefferson Headache Center/Thomas Jefferson University Hospital, Philadelphia, Pa.

OBJECTIVE: To evaluate olanzapine as a cluster headache abortive agent in an open-label trial. BACKGROUND: Cluster headache is the most painful headache syndrome known. There are very few recognized abortive therapies for cluster headache and fewer for patients who have contraindications to vasoconstrictive drugs. METHODS: Olanzapine was given as an abortive agent to five patients with cluster headache in an open-label trial. THE INITIAL OLANZAPINE DOSE WAS 5 MG, AND THE DOSE WAS INCREASED TO 10 MG IF THERE WAS NO PAIN RELIEF. THE DOSAGE WAS DECREASED TO 2.5 MG IF THE 5-MG DOSE WAS EFFECTIVE BUT CAUSED ADVERSE EFFECTS. To be included in the study, each patient had to treat at least two attacks with either an effective dose or the highest tolerated dose. RESULTS: Five patients completed the investigation (four men, one woman; four with chronic cluster, one with episodic cluster). Olanzapine reduced cluster pain by at least 80% in four of five patients, and TWO PATIENTS BECAME HEADACHE-FREE AFTER TAKING THE DRUG. Olanzapine typically alleviated pain within 20 minutes after oral dosing and treatment response was consistent across multiple treated attacks. The only adverse event was sleepiness. CONCLUSIONS: Olanzapine appears to be a good abortive agent for cluster headache. IT ALLEVIATES PAIN QUICKLY AND HAS A CONSISTENT RESPONSE ACROSS MULTIPLE TREATED ATTACKS. IT APPEARS TO WORK IN BOTH EPISODIC AND CHRONIC CLUSTER HEADACHE.

PMID 11576207 PubMed

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Olanzapine has a brand name of "Zyprexa" and is a antipsychotic. Don't be put off by this primary usage. Several of the drugs used to treat CH are cross over applications, that is, drugs approved by the FDA for one purpose which are found to be effective with unrelated conditions--BJ.
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The thing that works for me is to make sure whoever you're with knows you have to inject yourself.  Most of the people around me...co-workers, wife, friends etc all have a complete understanding as they've all seen me at least once in the middle of an attack. 

I've been everywhere from my bathroom at the house, airplane lavatory, movie theater, first building I could find when I was on the motorcycle, and most recently in a MRAP in the middle of Afghanistan.  Although I prefer the privacy of my own room I don't let that stop me.

I use the vials with insulin syringes and always have them on me.  I've found that 1ml is the minimum I need to knock one out after I was in Afghanistan and down to my last few vials before my refills made the 10 day trip in the mail.  Although sometimes that isn't enough more often than not it is.  Not to mention my supplies last longer and the side effects (someone sitting on my chest) aren't as pronounced.

I've flown well over 100 times in New Zealand and Australia carrying sumatriptan (imitrex) injectors without any issues at all. But do contact your airline to find out what rules apply for where you'll be flying.