Efficacy and Safety of Intravenous Neridronic Acid in CRPS

Inclusion Criteria: * Informed consent signed. * Male or female participant at least 18 years of age at Visit 1. * A diagnosis of CRPS according to the clinical diagnostic criteria recommended by the International Association for the Study of Pain (IASP; "Budapest clinical criteria"), assessed at Visit 1. Signs and symptoms of CRPS must apply to an affected limb (arm or leg) and must demonstrate asymmetry with respect to the contralateral limb. The CRPS duration must be 2 years or less since onset of symptoms. * A baseline average pain intensity score of greater than or equal to 4 using an 11-point numerical rating scale (NRS), referring to the CRPS-affected limb (average of pain recorded over 7 days). The baseline average pain intensity score will be calculated automatically by the electronic diary, which must be checked prior to allocation at Visit 2. A participant who has not met average baseline pain intensity requirements (at least 4 average pain intensity ratings) due to lack of compliance with the electronic diary may be rescheduled for Visit 2 (1 time only), with appropriate re-training to ensure compliance with use of the electronic diary. * In stable treatment and follow-up therapy for CRPS for at least 1 month prior to allocation to treatment (Visit 2). Participants must have failed attempts with at least 2 available treatments for CRPS, 1 of which must have been a pharmacologic treatment. * Women of child-bearing potential must have a negative urine Beta-human ch…