Which of the following agents requires supportive care as opposed to a specific antidote?

The agent that requires supportive care rather than a specific antidote is Dilantin, also known as phenytoin. In cases of phenytoin toxicity or overdose, supportive care is crucial as there is no specific antidote available. The management typically aims at stabilizing the patient's vital signs and providing symptomatic treatment. This may include monitoring cardiac function, controlling seizures, and ensuring airway protection, as phenytoin can cause neurological symptoms.

Supportive care is essential in overdose scenarios because it allows the medical team to address complications and maintain patient safety throughout the recovery process. Other agents listed may have specific antidotes or treatments targeted at counteracting their effects, which does not apply to Dilantin.