Safety and Preliminary Efficacy of BGP345A in Constipation Due to Opioid-based Medications

Inclusion Criteria: I1. Age over 18 years (limit included), I2. Diagnosed with OIC according to the adapted ROME IV criteria (Mearin F et al, 2016) previously used in clinical evaluation of patients with OIC (Webster LR et al, 2017) and self-reported symptoms assessed by a physician (daily diary check at V1 visit): * Fewer than three (\<3) spontaneous bowel movements (SBMs) per week. A SBM is defined as a bowel movement without the use of laxatives in the previous 24 hours as recorded in the daily diary. * And one or more of the following symptoms in at least 25% of bowel movements: straining, feeling of incomplete evacuation, and/or hard/small stools, defined as Bristol Stool Scale (BSS) score lower than 3 (\<3). I3. With chronic non-cancer pain since at least three months, including the following indications but not limited to: back-pain, rheumatisms and post-operative pain, I4. Patients received opioids for chronic analgesia (intended treatment ≥6 Weeks) for 1 week or more prior to study start and a stable regimen of opioids for 3 or more days before study entry (V0 visit) and during the whole study , I5. Subjects must be willing to discontinue laxative use at screening and only use the rescue laxatives permitted throughout the study duration, I6. For women: * Non menopausal with the same reliable contraception since at least 2 cycles before the beginning of the study and agreeing to keep it during the entire duration of the study (condom with spermicide gel, any o…