RDD1609 as a Treatment for Idiopathic Pruritus Ani

Inclusion Criteria: 1. An Institutional Review Board (IRB) approved informed consent is signed and dated prior to any study-related activities. 2. Male and female patients, age 18 - 65 years with idiopathic PA. 3. Screening VAS for itching of 60 mm and above. 4. Female subjects of child-bearing potential must have a negative urine pregnancy test. Females of childbearing potential must practice a highly effective method of pregnancy prevention (defined as \<1% pregnancies per 100 women per year) from one month before screening to one month after the follow-up visit, such as: surgical sterilization, hormonal implant, intrauterine device, or male condom + female diaphragm + vaginal spermicide. Female subject with any of the following circumstances is not required to use a highly effective method of pregnancy prevention: status post-hysterectomy; or, status post-tubal ligation; or, post-menopausal state (defined as \>= 12 months of spontaneous amenorrhea) or \< 12 months of spontaneous amenorrhea with a blood follicle stimulating hormone \> 40 MIU/ml. 5. Subject has normal (or abnormal and clinically insignificant) laboratory values at Screening. 6. Subject has the ability to understand the requirements of the study and a willingness to comply with all study procedures. 7. Subject has not used and agrees to abstain from taking any prescription or non-prescription medications, cosmetics, including herbal and dietary supplements (such as St. John's wort) within 7 days prior to the first dose of study medication (unless authorized by the Investigator and Medical Monitor). Exclusion Criteria: 1. Known hypersensitivity to RDD1609. 2. Known hypersensitivity to Mebendazole. 3. Previously treated with methylene blue for pruritus ani. 4. Randomization VAS for itching that is \<25 mm than the screening VAS. 5. Anorectal conditions such as malignant tumors of the anus and rectum, inflammatory bowel disease, fistulain- ano, fissure-in-ano, incontinence, condylomata, and second- and third-degree hemorrhoids and any other anorectal conditions that requires medicinal treatment. 6. Patients who had previous major proctological surgery. 7. Generalized skin disorders. 8. Active psychiatric disorders. 9. Diabetes mellitus all types. 10. Known to be HIV positive. 11. Current or within the last 4 weeks steroid or pregabalin or gabapentin or antihistamine systemic or local treatment.