Respond to the Needs in the Opioid War Act or the Respond NOW Act This bill establishes the Opioid Epidemic Response Fund through FY2024 to fund programs and activities addressing the opioid and substance use epidemic, including Substance Abuse and Mental Health Services Administration demonstration grants; Centers for Disease Control and Prevention surveillance, prevention, and treatment programs; Food and Drug Administration support of innovation in non-opioid and nonaddictive medical products for pain treatment; National Institutes of Health research on creating longer-lasting or faster-acting antidotes for opioid overdoses; Health Resources and Services Administration efforts to increase the availability and capacity of the behavioral health workforce; and Administration for Children and Families programs for child abuse prevention and treatment. The bill also extends funding through FY2024 for programs to help states and tribal organizations address substance use prevention and treatment, allows a practitioner to dispense narcotic drugs for maintenance treatment or detoxification treatment to an increased number of patients under specified conditions, and includes methadone treatment in Medicare coverage.