Which drug is used to counteract drug toxicity caused by magnesium sulfate during preterm labor management?

Calcium gluconate is the correct choice for counteracting drug toxicity caused by magnesium sulfate during preterm labor management because it acts as an antagonist to magnesium. When magnesium sulfate is administered, it can lead to elevated serum magnesium levels, which may result in adverse effects such as respiratory depression, diminished reflexes, and even cardiac issues. Calcium gluconate helps to restore calcium levels and counteract the neuromuscular blocking effects of excess magnesium, making it an essential drug in clinical settings where magnesium toxicity is a concern.

In contrast, magnesium oxide and phosphate buffer solution do not address the issue of magnesium toxicity; magnesium oxide is another form of magnesium that could potentially exacerbate the problem. Penicillin, an antibiotic, is unrelated to the management of magnesium toxicity and is used for treating bacterial infections, not electrolyte disturbances. Thus, calcium gluconate specifically targets the effects of excessive magnesium, making it the appropriate choice in this situation.