Monosodium Salt Pentobarbital is a barbiturate drug used for various purposes, including sedation and euthanasia. While there are many synonyms for this term, there aren't any direct antonyms, as it is a compound chemical name rather than a descriptive word. However, some possible antonyms could be "awake," "alert," "sober," or "conscious," as these words signify a state of being opposite to that achieved by using Monosodium Salt Pentobarbital. It's worth noting that barbiturate drugs can be dangerous if used improperly, so it's crucial to always speak with a doctor or licensed veterinarian before using them.