Sodium Stibogluconate Treatment of Leishmaniasis

Leishmaniasis is a protozoal disease transmitted by sandflies and is endemic in many parts of the world including Central and South America, Europe, Southwest Asia, Africa, and the Middle East. Infected humans may develop cutaneous (Old or New World), mucocutaneous (New World), or visceral leishmaniasis. The disease is a medical threat for military soldiers assigned in endemic areas and currently a major cause of morbidity in soldiers deployed to the Middle East and a complication of military exercises in Panama, Honduras, and South America.

Pentavalent antimonials (Pentostam, GSK, UK, and Glucantime, Rhone-Poulenc, France) have been used to treat leishmaniasis for more that 50 years. Neither of these drugs are licensed for commercial use in the United States, likely because of limited use. Worldwide, there is a great deal of experience and use of these products.

Pentostam or sodium stibogluconate is a pentavalent antimony drug complexed to carbohydrate the exact structure and mechanism of action of which are not known. It is provided as a 100 mg antimony/ml solution that contains a preservative, m-chlorocresol. Most of the dose is excreted by the kidneys within 24 hours.

Pentostam is presently an investigational new drug (IND) product that has been in use by the Department of Defense (DoD) for over 20 years for the treatment of cutaneous, mucosal and visceral leishmaniasis. In August, 1997, the FDA approved Ambisome (liposomal amphotericin) for the treatment of visceral leishmaniasis. As a result, in the treatment of visceral and viscerotropic leishmaniasis, the use of antimonials will now be considered a second-line therapy

In 1984, the World Health Organization recommended that the daily dose of antimony in the treatment of visceral leishmaniasis be increased to 20 mg/kg/day. A randomized controlled trial of 40 subjects with American, New World, cutaneous leishmaniasis (ACL) found 100% cure rates with 20 mg/kg/day Sb for 20 days but only a 76% cure if 10 mg/kg/day for 10 days was used. A comparison of three treatment schedules in 36 subjects with CL (single rapid infusion, continuous 24 hour infusion, or every eight hour doses) found no advantage over using once daily dosing. A review of the controlled trials of SSG concludes that a recommended course of therapy is 20 mg/kg/day with no upper limit to dose for 20 days for CL and 20 mg/kg/day for 28 days for visceral or mucocutaneous leishmaniasis. The Pentostam® package insert suggests that 10-20 mg/kg/day with a maximum dose of 850 mg for a minimum of 20 days be used; however, based on the Centers for Disease Control and Prevention (CDC) and Walter Reed Army Medical Center (WRAMC) experience and their practice guidelines, 20 mg/kg/day with no upper limit to dosage is used. WRAMC recently published their CL treatment experience primarily in New World leishmaniasis comparing SSG 20 mg/kg for 10 or 20 days and found 100% of volunteers in the 10-day group were cured. In this study 15% were Leishmania major infections. Comparable results are expected for Old World leishmaniasis based on clinical experience and current literature.

Detailed toxicity data for the 20 mg/kg/day dose are provided by several studies. Percentages from the WRAMC experience are included here. Subjective musculoskeletal complaints are common (58%), as well as elevated hepatocellular (67%) and pancreatic enzyme levels (97%) and nonspecific electrocardiogram (EKG) changes (T wave changes). These side effects are usually reversible, and no deaths have been associated with SSG at WRAMC. Other SSG toxic effects include headache (22%), rash (9%), thrombocytopenia, depression of various hematologic cell lines (44%), phlebitis, anaphylaxis, inflammation around lesions, and transient coughing after infusion. Other associated symptoms include anorexia, malaise, myalgia, abdominal pain, headache, lethargy, sweating, vertigo, facial flushing, initial worsening of skin lesions, epistaxis, jaundice and peripheral neuropathy. In our above-mentioned 10 versus 20 days study, the adverse events (AE) were significantly decreased in the cohort receiving the 10 days versus 20 with myalgias in 42% (versus 68%), with less chemical pancreatitis and fewer hematologic parameter disorders. Angioedema during SSG infusion has recently been described in two subjects at WRAMC. Both subjects responded quickly to benadryl treatment without complications. Both subjects were subsequently skin tested with SSG intradermally for hypersensitivity and one reacted.

Alternative heat therapies have been used to successfully treat CL. Laboratory investigation showed that Leishmania infection is sensitive to heat. Various forms of heat application in human CL has shown variable efficacy. The TTI Thermomed™ device has been cleared as a 510-k device by the U.S. Food and Drug Administration (FDA) for use in the treatment of CL. This device uses localized current field radio frequency. Other therapies that may be effective for treating CL include topical paromomycin and oral fluconazole.