The purpose of this study is to determine whether adding pentoxifylline to treatment of American cutaneous leishmaniasis with meglumine antimoniate increases the rate and speed of clinical response without diminishing safety, and to identify immune correlates of the healing response.

Failure of first line therapies for cutaneous leishmaniasis is a public health issue. Since pathogenesis of dermal leishmaniasis is mediated by the immune and inflammatory responses, resolution of disease and control of infection are intimately linked to the host response. Several investigations have substantiated "proof of principal" for the therapeutic gain of co-adjuvant immunotherapy. This study will evaluate the efficacy and safety of using pentoxifylline (PTX) as a co-adjuvant in the treatment of cutaneous leishmaniasis with meglumine antimoniate in a randomized, double-blind, controlled trial. One arm will receive meglumine antimoniate and PTX and the other arm will receive meglumine antimoniate plus placebo. Efficacy will be assessed at the end of the treatment, and 5, 7, 13 and 26 weeks after initiation of treatment. Efficacy will be measured as the proportion of patients with definitive cure at 26 weeks after initiation of treatment, and time to healing. Safety will be assessed at the end of treatment with respect to the frequency and severity of adverse events.

Blood samples will be taken to evaluate the effects of PTX invitro and ex vivo on cells of the immune system. Proliferation and secretion of cytokines relevant to the immune and inflammatory responses by peripheral blood mononuclear cells will be measured before and after treatment. Likewise, macrophages will be differentiated from peripheral blood monocytes and infected with a strain of L. panamensis transfected with the luciferase (luc) gene. The investigators will measure the capacity of patient macrophages to kill parasites before and after treatment using a luminometric assay of viable parasite burden. Additionally, the investigators will measure the expression of inducible nitric oxide synthase, an enzyme that is necessary for nitric oxide production, one of the main leishmanicidal mechanisms used by macrophages. The investigators postulate that the use of the co-adjuvant with antimonials will increase the therapeutic response and that indicators predictive of a healing response can be identified by this prospective analysis of the immune response and therapeutic outcome.

Inclusion Criteria:

• Patients with clinical diagnosis of cutaneous leishmaniasis (parasitologic confirmation or presumptive biopsy plus a positive Montenegro skin test).
• Age between 18 and 65 years.
• Lesions of a duration equal to or greater than one month
• More than one lesion or single lesion greater than 3 cm in diameter.
• Willingness to participate in the study after being informed through a consent process approved by the institutional ethical review committee

Exclusion Criteria:

• Pregnant or lactating women, and women who are planning to conceive during the study or that reject the use of birth control methods.
• Medical conditions that compromise the immune system (HIV infection, neoplasias, diabetes mellitus, autoimmune diseases, or use of corticosteroids, immunomodulators or antineoplastic drugs).
• Medical conditions that preclude the use of antimonials or pentoxifylline (cardiac, renal, hepatic or pancreatic disease or abnormalities).
• Alcohol abuse or use of recreational drugs that interfere with adherence to treatment
• Use of drugs with antileishmanial potential during the previous 13 weeks, including pentavalent antimonials, amphotericin B, miltefosine, and pentamidine
• Use of Theophylline , anticoagulants or antiarrhythmics.
• Diffuse or disseminated leishmaniasis.
• Mucosal involvement secondary to Leishmania infection.
• Incapacity to attend the study visits or any other condition that according to the investigator could interfere with adherence to study procedures.