Efficacy and Safety of Topical Versus Systemic Treatment in Postherpetic Neuralgia and Diabetic Polyneuropathic Pain

Inclusion Criteria: * Male or female subjects with \>= 18 years of age * Intact skin in the area of topical treatment * Creatinine clearance CLCR \>= 30 mL/min * NRS-3 \> 4 (recalled average pain intensity during the last 3 days) Subjects with DPN * Controlled, treated type 1 or 2 diabetes mellitus with glycosylated hemoglobin (Hba1c)\<= 11% * Painful, distal symmetrical, sensomotor polyneuropathy of the lower extremities for \>= 3 months (below the knees on both extremities) with at least 2 of the following symptoms present: burning, sensation, tingling or prickling, numbness from time to time, painful heat or cold sensation (e.g. warm or cold water) Subjects with PHN * Subjects with PHN and neuropathic pain present for \>= 3 months after healing of the herpes zoster skin rash. * Without neurolytic neurosurgical therapy for their condition. Exclusion Criteria: General * Evidence or history of alcohol, medication or drug abuse and/or dependency in the past 2 years, unstable psychological personality requiring intermittent or permanent treatment. * Psychiatric illness (subjects with well-controlled depression or anxiety disorder may participate if they are not taking any of the prohibited medications defined (below), epilepsy or suicide risk. * Pregnant or breastfeeding women * Women of childbearing potential who are sexually active without satisfactory contraception for at least 28 days prior to enrollment, during the trial, and until 28 days after the follow-up visit. * Subjects with severe cardiac impairment e.g. NYHA class \> 3, myocardial infarction less than 6 months prior to enrollment, and/or unstable angina pectoris. * Subjects with severe hepatic disorder and/or AST or ALT \>= 3x the upper limit of normal. * Subjects with known or suspected severe renal failure (CLCR \< 30 mL/min). * Anticipated need for surgery during the trial, requiring at least regional or general anesthesia. * Subjects who are undergoing active treatment for cancer, are known to be infected with HIV or being acutely and intensively immunosuppressed following transplantation. * Participation in another trial of investigational medicinal products or devices parallel to or less than 1 month before entry into the trial, or previous participation in this trial. Trial specific: * Any concomitant use of drugs for the treatment of neuropathic pain or commonly used for the treatment of neuropathic pain. * Use of transcutaneous electrical nerve stimulations (TENS) after enrollment. * CLCR \< 30 mL/min * Evidence of another cause for pain in the area of neuropathic pain such as lumbar radiculopathy, surgery trauma, restless legs syndrome, if this coud confound the assessment or self-evaluation of the neuropathic pain. * Presence of other severe pain that could confound the assessment or self-evaluation of the neuropathic pain. * History of malignancy within the past 5 years (with the exception of basal cell carcinoma). Subjects with PHN * Active herpes zoster lesion or dermatitis of any origin at the affected site with PHN. * Subjects who had neurological ablation by block or neurosurgical intervention for control of pain in PHN. Subjects with DPN * No palpable pulse of the arteria dorsalis pedis in both feet. * Clinical signs for venous insufficiency and/or postthrombotic syndrome Sage III/IV (i.e. extensive varicoses) * Ulcers on the lower extremities.