Which of the following medications may be delivered by instillation down the ETT during ACLS efforts?

During Advanced Cardiac Life Support (ACLS) efforts, atropine is a medication that can be administered via endotracheal tube (ETT) instillation. Atropine is an anticholinergic agent used primarily to treat bradycardia, as it increases heart rate by inhibiting the vagus nerve's effect on the heart. In emergency situations, when intravenous access is not readily available, administering atropine through the ETT provides a viable alternative to ensure rapid therapeutic effect.

The other medications listed are generally not provided through ETT. For instance, prostaglandin is typically used for conditions like cardiovascular issues or labor induction, while racemic epinephrine is used primarily as a topical agent in cases like croup rather than for systemic effects in an ACLS context. Nitroglycerine, a vasodilator, is usually administered intravenously or sublingually, as its delivery through an ETT would not ensure effective therapeutic levels due to absorption issues. Thus, the strong evidence supporting the administration of atropine via ETT makes it the correct choice for this question.