Sumitriptan Injections - past use by date - safe to use?

Hello all. I'm a long term ECH sufferer who had been on a blissful 30 month remission.

Yay - must be cause I'm getting older!

I'm now anticipating the return of my nemesis as I'm getting shadow headaches and single attacks which is really weird.

During my last bout there was a national shortage of injections due to a batch recall and there were none to be had for love nor money. It was horrendous. At the time I swore that I would never run short again. I retained about a weeks supply once the attacks were over. I would be suprised if most ECH sufferers don't do the same TBH.

Anyway - enough rambling. I revisited my stockpile of injections the other day to find that, not unexpectedly, they were all out of date. The use by date on these is 09/15.

So my question is quite simple. Can I safely use these now or are they only fit for the bin? 

I know the stock answer is that they may have degraded, be potentially unstable, might make you more ill etc etc but like use by dates on food, is that just put there by the manufacturer to shift units or is there a real danger if I use these?

I have used three of the old stock already because I needed to and didn't have access to fresh stocks. It worked as well as I remember and I haven't suffered any unusual symptoms or problems.

I now have some fresh refills and could probably bin the old stock but loathe to waste it unless I have to, especially given the cost of the shots.

Any thoughts?

Cheers

Kit