Exclusion criteria: <br>1. Medical condition or illness other than solid neoplasm that would, in the opinion of the Investigator, preclude study participation or interfere with the assessment of pain<br>2. Abnormal liver or kidney function as defined by alanine aminotransferase (ALT), aspartate aminotransferase (AST) or alkaline phosphatase in excess of 3 times the upper limit of normal, or chronic kidney disease worse than stage II (glomerular filtration rate <60 mL/min as calculated by Cockroft-Gault formula [(140-age) x (weight in kilograms) x (0.85 if female) / (72 x serum creatinine in mg/dl)])<br>3. Significant pain with neuropathic features which cannot be attributed to underlying malignancy<br>4. Proven hypersensitivity to flupirtine or one of the other ingredients<br>5. Cholestasis, pre-existing liver disease, or at risk of hepatic encephalopathy<br>6. Use of paracetamol-containing medications or carbamazepine<br>7. History of radiotherapy or a nerve block or other anesthetic procedure to the presumed site of nerve damage within 4 weeks preceding the Screening Visit (Day -7). Such procedures after the Screening Visit will necessitate withdrawal from the study.<br>8. If receiving a bisphosphonate medication, change in dose or frequency within 3 months preceding the Screening Visit (Day -7)<br>9. If receiving a hormonal contraceptive, change in dose or frequency within 3 months preceding the Screening Visit (Day -7)<br>10. Systemic radioisotope therapy within 1 month preceding the Screening Visit (Day-7)<br>11. Significant history of illicit drug or alcohol abuse<br>12. Current or previous (within 30 days of first study dosing) treatment with another investigational drug or participation in another clinical study<br>13. Change in chemotherapy regimen anticipated within 6 weeks following the Screening Visit<br>14. Pregnant or lactating females. Serum pregnancy test must be performed within 7 days prior to study treatment start, or within 14 days with a confirmatory urine pregnancy test within 7 days prior to study treatment start;<br>15. Known hepatitis B or C or HIV infection<br>16. Not suitable for study participation in the Investigator’s judgment<br>17. Previous participation in this study<br>18. Patient is a relative of, or staff directly reporting to the Investigator<br>19. Patient is an employee of the sponsor<br>20. Subject is committed under official or judicial order<br>21. Patient with a known diagnosis of myasthenia gravis<br>22. Patient with a known diagnosis of tinitus<br>23. Patients with metastatic liver disease (accompanied by change in LFTs to >2x ULN)<br><br><br>