Antonyms for the state of somnolence, which is feeling drowsy or sleepy, could include the opposite, such as alertness, wakefulness, or energy. Somnolence can be characterized as a lack of mental or physical activity and loss of consciousness, so antonyms would be those indicating an active and awakened state of being. For example, "in vigilance," "in awareness," or "in activity" would be stark contrasts to the feeling of being in somnolence. Additionally, words like vitality, liveliness, and fervor could all be seen as antonyms for somnolence, as they represent an active and vibrant energy.