The Effect of Intra-anal Nifedipine, Used As Add-on to Conservative Therapy, on Pain in Patients With Anal Fissure

Inclusion Criteria: \- Subjects meeting the following criteria will be eligible to participate in the trial: 1. Single anal fissure; 2. Signed written informed consent; 3. Male or female subjects 18 to 65 years of age inclusive; 4. Has chronic anal fissure defined as history of rectal pain at least three days a week for at least 6 weeks - or more AND at least one of the following: * Sentinel skin tag * Hypertrophied anal papilla * Exposure of the underlying internal anal sphincter * Anal cicatrisation 5. Visual analogue scale of average 24 hours rectal pain (VAS) of \> 40 mm in screening visit 6. Capable of using the IVRS and able to adequately communicate comprehension of the IVRS questions to the investigator 7. If female, is non-lactating, has a negative urine pregnancy test result, and does not plan on becoming pregnant during the study, or not of childbearing potential (hysterectomy or tubal ligation at least 6 months prior to entry to the study or post-menopausal for 1 year); if of childbearing potential (including peri-menopausal women who have had a menstrual period within one year) must practice or be willing to continue to practice acceptable birth control from screening and until 1 week after the study medication has been discontinued. Acceptable birth control includes : * combined (estrogen and progestogen containing) hormonal contraception * associated with inhibition of ovulation; oral OR intravaginal OR transdermal. * progestogen-only hormonal contraception associated with inhibition of ovulation: oral OR injectable OR implantable. * progestogen-only oral hormonal contraception, where inhibition of ovulation is not the primary mode of action * intrauterine device (IUD) * intrauterine hormone-releasing system ( IUS) * bilateral tubal occlusion * vasectomised partner * sexual abstinence * male or female condom with or without spermicide * cap, diaphragm or sponge with spermicide Exclusion Criteria: * Subjects are excluded from participation in the study if any of the following criteria apply: 1. Known allergy to Nifedipine 2. Unwilling to stop all other concomitant topical preparations applied in and around the anus from screening through the end of the study 3. Subfissure injection of botulinum toxin in the 3 months prior to screening. 4. Fissure resulting from inflammatory bowel disease, venereal disease, perianal psoriasis, immunodeficiency syndrome 5. Atypical fissure (occurs off the midline) in which secondary causes were not excluded. 6. Deemed by the investigator as anal fissure for which surgery is indicated 7. Anal abscess; 8. Grade 4 hemorrhoids 9. Fixed anal stenosis 10. Active or past history of cardiovascular or cerebrovascular disease including but not limited to angina pectoris, myocardial infarction, transient ischemic attacks/stroke, arrhythmia or ecg changes that requires medical treatment or deemed by the investigator as clinically significant, moderate to severe congestive heart failure, or cardiac valve abnormalities; 11. Type 1 diabetes mellitus 12. Insulin treated type 2 diabetes mellitus 13. Renal failure defined as a serum creatinine \> 1.5 mg/dL (133 µmol/L) at screening 14. Liver disease defined as Aspartate aminotransferase (AST) or alanine aminotransferase(ALT) \>2 X upper limit of normal at screening 15. Malignant disease within 3 years of screening 16. Has uncontrolled hypertension (sitting blood pressure \>160/95 mmHg at screening) 17. Has hypotension (blood pressure lower than 90/60 mm Hg at screening) 18. History of chronic gastrointestinal disease such as Crohn's disease or ulcerative colitis 19. History of major rectal surgery 20. History of HIV, Hepatitis B, Hepatitis C 21. Has clinical laboratory test values (chemistry, hematology, or urinalysis) judged to be clinically significant by the investigator at screening; 22. Has used, in the last two weeks, drugs that may affect blood coagulation, such as Aspirin at a dose higher than 500 mg/day, Warfarin, Sintrom, Enoxaparin, Nadroparin, Heparin, Clopidogrel, Ticlopidine Rivaroxaban, Apixaban, Edoxaban 23. Is treated with drugs that may affect the anal sphincter: 1. Calcium channel blockers such as Nifedipine, Diltiazem or Verapamil 2. Nitroglycerin or nitrates 24. Has, upon physical examination, a rectal deformation or signs of rectal disease such as fistula, infection or space occupying lesion; 25. Participated in a clinical study in the last 30 days prior to screening. 26. Is an immediate family member of personnel directly affiliated with the study at the investigative site, or is personally directly affiliated with the study at the investigative site; or is employed or related to the Sponsor, CRO or investigator;