You are answering a USMLE-style medical question. Question: The first 24 hours after delivery, a 2888 g (6.37 lb) male newborn is not feeding well, has a high-pitched cry, and is diaphoretic. He was born at 38 weeks' gestation to a 30-year-old woman, gravida 2, para 1, after an uncomplicated labor and delivery. Apgar scores were 8 and 9 at 1 and 5 minutes, respectively. The mother did not receive prenatal care. She takes codeine syrup frequently for dry cough. The infant's temperature is 37.8°C (100°F), pulse is 165/min, and blood pressure is 83/50 mm Hg. Examination shows hyperreflexia, tremors, and an excessive startle response. The baby is swaddled to prevent excoriations, and fluid resuscitation is initiated. Complete blood count and serum levels of glucose, bilirubin, and calcium are within normal limits. What is the most appropriate next step in treatment of this newborn? Options: A) Oral morphine therapy B) Intravenous ampicillin and gentamicin combination therapy C) Oral methimazole therapy D) Dextrose infusion Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.