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.