Use of topical phenytoin and loperamide for the treatment of neuropathic pain

INTERVENTION: The study design is interventional, employing a double‐blind randomized controlled design. Patients will receive either a test cream or a placebo, randomized in the hospital's apothecary, and various aspects of neuropathic pain will be assessed at different time intervals. The study will take place at the University Hospital of Maribor, making it a single‐centred study. The study was designed in accordance with the CONSORT statement. Patients who scored at least 4 points on the DN‐4 questionnaire and had pain severity of at least 4 on the numeric rating scale (NRS) at the appointment or in the last 24 hours will be enrolled on the study after receiving information about the study and providing written consent. Participants in the study will be randomly allocated to one of two groups based on a computer‐generated list of random numbers by a non‐investigator who also concealed the group allocation by putting the group assignments (in a 1:1 ratio) in sequentially numbered opaque envelopes. Each envelope will be later opened by the pharmacist after the patient’s consented enrolment and after placing the patients name sticker on the envelope. After enrolment, each patient will complete two validated questionnaires: the Neuropathic Pain Symptom Inventory (NPSI) and EQ‐5D Health Status Questionnaire. Then, the investigators will apply 1.2 g of either the test cream, consisting of Pentravan base cream, 25% propylene glycol, 20% phenytoin, and 5% loperamide, or a placebo cream consisting of Pentravan base cream, tablettose (sucrose for identical cream texture) and 25% propylene glycol. Forty‐five minutes after the application of the cream, patients will rate the pain severity with the NRS. If there are no side effects, patients will be provided with the same cream for home us CONDITION: Treatment of peripheral neuropathic pain ; Nervous System Diseases PRIMARY OUTCOME: Pain measured using a Numeric Rating Scale (NRS) at baseline before the first application of the cream, 45 min after the first application of the cream, 48h after the first application and 14 days after the first application; ; ; INCLUSION CRITERIA: 1. Patients experiencing peripheral neuropathic pain and currently under treatment at the Pain Management Clinic of the Department of Anesthesiology, Intensive Therapy, and Pain Management at the University Medical Centre Maribor 2. Adults identified with neuropathic pain using the DN‐4 questionnaire, scoring at least 4 points out of 10 SECONDARY OUTCOME: 1. Health‐Related Quality of Life measured using the EQ5D questionnaire total score at baseline, 14 days after treatment; 2. Neuropathic Pain measured using the Neuropathic Pain Symptom Inventory (NPSI) questionnaire at baseline, 14 days after treatment; 3. Placebo Effect measured using the Numeric Rating Scale (NRS) at baseline, 45 minutes after the first application, 48 hours after the first application, 14 days after the first application; 4. Subgroup Analysis (for patients with post‐herpetic neuralgia) measured using the Numeric Rating Scale (NRS) for pain, EQ5D questionnaire total score for health‐related quality of life, Neuropathic Pain Symptom Inventory (NPSI), Categorized pain relief scale at baseline, 45 minutes after the first application, 48 hours after the first application, 14 days after the first application, Daily measurements; 5. Average Pain Level measured using the Numeric Rating Scale (NRS) daily; 6. Average Pain Relief measured using the Categorized pain relief scale daily