Final answer:
To reduce the postnatal effects of Demerol on the neonate, Naloxone (Narcan) should be available.
Step-by-step explanation:
To reduce the postnatal effects of Demerol on the neonate, the medication that should be available is Naloxone (Narcan). Naloxone is an opiate antagonist that can reverse the respiratory depression caused by narcotics, including Demerol. It is often used in newborns of mothers who have received narcotics to counteract the effects of the drug.