Cough Reduction in IPF With Nalbuphine ER

The main purpose of the study is to evaluate the effect of NAL ER on 24-hour cough frequency using objective digital cough monitoring and to assess safety and tolerability of NAL ER.

Inclusion Criteria: * Diagnosis of IPF as determined by the Principal Investigator based on ATS/ERS/JRS/ALAT guidelines. * Cough Severity Score ≥ 4 on CS-NRS (Cough Severity Numerical Rating Scale) during the Screening period and Baseline. * History of chronic cough for at least 8 weeks before screening. * SpO2 ≥ 92%, taken after at least 5 minutes in a sitting position, undisturbed and non-stimulated (Saturation of Hemoglobin with Oxygen as Measured by Pulse Oximetry). * FVC ≥ 40% predicted of normal - Forced Vital Capacity, as determined by spirometry adhering to ATS/ERS guidelines. * DLCO ≥ 25% predicted of normal - Diffusing capacity of the lung for carbon monoxide corrected for hemoglobin, assessed within the last 12 weeks, or at the time of screening. Exclusion Criteria: * Currently on continuous oxygen therapy for longer than 16 hours at any level or delivered by any modality. Intermittent oxygen use of any duration over any given 24-hour period is allowed. * Inadequate swallow reflex as assessed by the ability to sip 3 fluid oz (or 89 mL) of water without coughing or choking. * Upper or lower respiratory tract infection in the last 8 weeks prior to the baseline visit. * Clinical history of aspiration pneumonitis. * Diagnosis of sleep apnea. * Abnormal kidney or liver functions based on Screening lab results. * Known hypersensitivity to nalbuphine or to NAL ER excipients * History of major psychiatric disorder. * History of substance abuse. * Significant medical condition or other factors that may interfere with the participant's ability to successfully complete the study. * Pregnant or lactating female participant. * Known intolerance (gastrointestinal, central nervous system symptoms), hypersensitivity, drug allergy following the use of an opioid drug. * Use of opiates is prohibited within 14 days prior to the baseline visit. * Use of benzodiazepines are prohibited within 14 days prior to the baseline visit and for the duration of the study. * Monoamine oxidase inhibitors (MAOIs) including methylene blue (methylthioninium chloride) and the antibiotic linezolid are prohibited within 14 days prior to the baseline visit and for the duration of the study. * Use of oral corticosteroid cough treatment is prohibited within 4 weeks prior to the baseline visit and for the duration of the study. * Exposure to any investigational medication, including placebo, is prohibited within 4 weeks prior to the baseline visit and for the duration of the study. * Medications prescribed as cough suppressants are prohibited unless on a stable dose 14-days prior to the baseline visit and are expected to remain on that dose for the duration of the study. * Use of medications that affect serotonergic neurotransmission and that when used concomitantly with opioids can increase the risk of serotonin syndrome are prohibited unless on a stable dose 14-days prior to the baseline visit and are expected to remain on that dose for the duration of the study. * Anti-fibrotic medications are prohibited unless on a stable dose for 8 weeks prior to the baseline visit and are expected to remain on that dose for the duration of the study. * Strong inhibitors/inducers of the P450 Isozymes are prohibited unless on a stable dose for 14-days prior to baseline visit and are expected to remain on that dose for the duration of the study. * Use of a medication having a "known risk" of Torsade de Pointes (categorized as "KR" on the Credible Meds® website.) 4 weeks prior to Baseline. * Use of unstable doses of medications associated with a potential risk of QT prolongation but not clearly associated with Torsade de Pointes within 4 weeks of screening. Other protocol defined inclusion/exclusion criteria may apply.