Study of the Efficacy, Safety and Tolerability of Topical 2PX (Strontium Chloride Hexahydrate) in Patients With Chronic, Moderate-to-severe Lower Limb Post-amputation Stump Pain

Inclusion Criteria: * Lower limb amputation at least 6 months prior to Visit 1. Amputation must be transtibial, transfemoral or through the knee. For patients with transfemoral amputation, the point of amputation must be ≥10 cm from the inguinal region. * Presenting with moderate-to-severe stump pain. For the purpose of this study, the following criteria must all apply: 1. Stump pain commencing post amputation and continues at Visit 1 despite continued use of analgesic medication 2. Stump pain present on a daily basis 3. Stump pain intensity as Average stump Pain Intensity (AsPI) ≥40 on 100 mm VAS at Screening 4. Stump pain intensity at the randomisation visit: Mean (over the 7 day run-in period) AsPI rating ≥40 on a 100 mm VAS. 5. Pain at the site of the extremity amputation. The pain is located mainly in the stump itself. (Patients with concurrent phantom pain may be enrolled in the study.) 6. Stump pain persists despite proper healing of the stump * Outpatients, aged 18 years and above * Underlying therapy (e.g., rehabilitation procedures, analgesia, physio-therapy, spinal cord stimulation (except for topical or subcutaneous local analgesics)) may be continued throughout the duration of the study, if the regimen has been stable during the 4 weeks immediately prior to Visit 1. If underlying therapy is continued during the study the regimen must be maintained for the duration of the study. * Written informed consent Exclusion Criteria: * Patients with forefoot amputations alone are excluded from participation. * Patients who have received treatment with any topical or subcutaneously administered analgesic agent for stump or phantom pain in the 4 weeks prior to study entry (i.e. Visit 1). * Underlying therapy (e.g., rehabilitation procedures, analgesia, physio-therapy, spinal cord stimulation) is not permitted if the regimen has not been stable in the 4 weeks immediately prior to Visit 1. * After the 7 day run-in phase: patients taking any new or changing the dose of any underlying analgesic medication (except for rescue medication as defined in this protocol). * Patients with open wounds, burns or other non-intact skin at site(s) of study drug administration (unhealed stumps). * Patients with significant discomfort from their prosthesis limiting use of the prosthesis. Use of a prosthesis is not a requirement for participation in the study. * Pregnancy * Female patients of childbearing potential unwilling to use adequate contraception measures throughout t…