Final answer:
The nurse should anticipate administering calcium gluconate as an antidote if magnesium sulfate toxicity is suspected in a patient receiving IV magnesium sulfate.
Step-by-step explanation:
If a nurse suspects magnesium sulfate toxicity in a client receiving IV magnesium sulfate, the medication that should be administered is calcium gluconate. Calcium gluconate acts as an antidote to magnesium sulfate toxicity by counteracting the effects of excess magnesium on the neuromuscular junction. In the presence of high levels of magnesium, calcium administration can help restore normal neuromuscular function.