Analeptic refers to something that restores or invigorates. Its antonyms can be words that connote lethargy, weakness or loss of energy. One such opposite of analeptic is lethargic, which signifies a lack of energy or enthusiasm. Other antonyms can include words like weak, powerless or insipid. For instance, when we say that our energy levels are low or when we lose motivation, we are quite often experiencing the opposite of what analeptic represents. Analeptic is a term used when we need something that keeps us alert and fresh, so its antonyms are important to understand when we are feeling sluggish or run-down.