antidotal

The story

1. Proto-Indo-European*h₂ent-
2. Proto-Indo-European*h₂énts
3. Proto-Indo-European*h₂énti
4. Ancient Greekᾰ̓ντῐ́ (ăntĭ́)
5. Ancient Greekᾰ̓ντῐ- (ăntĭ-)
6. Proto-Indo-European*deh₃-redup.
7. Proto-Indo-European*dédeh₃ti
8. Proto-Hellenic*dídōmi
9. Ancient Greekδῐ́δωμῐ (dĭ́dōmĭ)
10. Ancient Greekᾰ̓ντῐδῐ́δωμῐ (ăntĭdĭ́dōmĭ)
11. Ancient Greekᾰ̓ντῐ́δοτος (ăntĭ́dotos)
12. Latinantidotum
13. Englishantidote
14. Proto-Indo-European*h₂el-
15. Proto-Indo-European*h₂élisder.?
16. English todayantidotal

From antidote + -al.