PK, PD and Safety Comparative Trial of Isosorbide Mononitrate Gel in Healthy Participants and With Anal Fissure

Inclusion Criteria: * Male and female subjects aged ≥ 18 years-old; * Body mass index (BMI) ≥ 19 Kg/m2 and ≤ 35 Kg/m2; * For healthy volunteers: good health conditions or without significant diseases, according to best medical judgement, according to protocol requirements and study evaluations: medical history, blood pressure and heart rate measurements, physical examination, electrocardiogram (ECG) and screening laboratory tests; * For participants with the condition under study: anal fissure; * Ability to understand the nature and objectives of the trial, including risks and adverse events; willingness to cooperate with the researcher and proceed according to all study requirements, which shall be confirmed by Informed Consent Form signature. Exclusion Criteria: * Known hypersensitivity to the investigational products (naproxen or rebamipide) or chemically related compounds; history of serious adverse reactions or hypersensitivity to any drug; * Chronic therapy with any drugs, except oral contraceptives and medication authorized by principal investigator (each case to be individually evaluated); * History of hepatic, kidney, lungs, gastrointestinal, epileptic, hematologic or psychiatric disease; hypotension or hypertension, or any other co-morbidity that requires priority immediate treatment ot that, at principal investigator discretion, might interfere with study participation or expose study participant to risks other than predicted; * Deviations on screening laboratory results that are considered as clinically relevant by the principal investigator; * Smoking; * History of drugs and alcohol addiction or excessive alcohol consumption (\> 35 g/ day); * Use of regular medications within 2 weeks prior study enrollment or use of any medications within one week prior to study enrollment, except oral contraceptives or cases which, based on drug's or metabolite's half-life, complete elimination can be assumed; * Treatment, within 6 months before the trial, with any drugs known to have a well established toxic potential to major organs; * Participation in any other experimental research or administration of any experimental drug within six months before this trial; * Donation or loss of 450 mL of blood (or more) within 3 months before the trial, or 4 donations within 12 months before the trial; * Any condition, according to investigator's best judgement, that prevents the subject to participate in the trial; * Pregnancy, labor or miscarriage with 12 weeks before admission predicted date.