 This study is a Phase 4, open-label, single group study in which at least 40 adult patients undergoing miltefosine treatment for mucocutaneous leishmaniasis will be assessed by digital 12-lead electrocardiogram ECG for prolongation of the QTc interval. Potential subjects diagnosed with mucocutaneous leishmaniasis who are planning to undergo miltefosine treatment will be informed about the study and undergo the informed consent process. After obtaining informed consent, subjects will be screened over a 14-day period for eligibility by medical history including leishmaniasis diagnostics, physical examination, clinical laboratory measurements chemistries: alanine aminotransferase ALT, total bilirubin, creatinine, magnesium, calcium, potassium, sodium; hematology: white blood cell WBC count, hemoglobin, platelet count; and a pregnancy test if female, ECG, and medication use in the 28-day period before starting treatment. If eligible for the study, the subject will receive miltefosine for 28 days at a target dose of approximately 2.5 mgkgday. Screening and enrollment into the study will continue until at least 10 females and up to 30 males complete the study and are considered evaluable provide Day 28 ECGs and PK samples and complete at least 25 of 28 days of miltefosine treatment. Vital signs will be collected weekly during treatment. Chemistries and hematology will be repeated at study Days 14 mid-treatment and 28 end of treatment. A pregnancy test if applicable will be repeated at Day 28. ECGs 12-lead will be repeated at Days 14 and 28. Blood will be drawn for pharmacokinetic PK assessments on Days 14 and 28 within 15 minutes of the final ECG. Adverse events AEs and concomitant medication use will be collected during treatment. If on Day 28, clinically significant abnormalities are observed by ECG, then a repeat ECG and PK blood draw will be performed at Day 42 2-weeks after completing treatment. AEs and concomitant medication use will also be collected in any subject coming back for the Day 42 visit. Digital ECGs 12-lead will be collected in triplicate at each time point over a period not to exceed 1 hour. During treatment, ECGs will be collected 4 hours after a dose approximate Tmax. 