Hi @Sumari, sorry I don't know the availability status of imigran injections.
If your dad has any left, and if they are 6 mg, he can actually get 3 aborts, instead of just one, from one syringe, with the extending imitex tip successfully used by legions of clusterheads for a good couple decades now.
I imagine it is the only prescription medicine that has helped so far, but non-pharmaceutical approaches have been found to be more effective, with high success rates, as seen at the blue New Users - Please Read Here First banner at the top of the page ^^^^.
Also if 100% oxygen at a high flow rate is at all available, it is a non-toxic abortive that can be an effective replacement for imigran in most instances.