title: Resistance of infection by Plasmodium vivax to chloroquine in Bolivia.
abstract: BACKGROUND
  Chloroquine (CQ) over three days plus primaquine (PQ) for seven days is the treatment of choice of infections by Plasmodium vivax in Bolivia, where 95% of the cases of malaria are attributed to this species. The aim of this study was to evaluate the therapeutic efficacy of CQ in this setting.
  
  
  METHODS
  Patients in the Amazon region of northern Bolivia, were included in the study from May to November 2011 and the therapeutic efficacy of CQ was evaluated over a 28-day follow-up period. Patients with P. vivax mono-infection received 25 mg/Kg body weight of CQ over three days. The concentrations of CQ + desethylchloroquine (DCQ) in blood were determined at days 7 and 28 of follow up; at follow-up and on the day of treatment failure was administered PQ.
  
  
  RESULTS
  One hundred patients fulfilled the inclusion criteria, two were lost to follow up and another two were later excluded for protocol violation. Of the 96 patients who completed the follow up 10 showed TF; one presented continued parasitaemia until day 7 of follow up, three on day 21 and six on day 28 of follow up. The geometric mean of CQ + DCQ on day 7 was 321.7 ng/ml (range 197-535 ng/ml). In six patients with TF the CQ + DCQ concentrations in blood on the day of TF were >100 ng/ml. The rate of resistance was 6.5%.
  
  
  CONCLUSIONS
  The present study demonstrates the presence of resistance to CQ in the treatment of malaria by P. vivax in the Amazon region of Bolivia. New clinical trials are needed to establish alternative treatments against these parasites in this region of South America.
authors.affiliation: Departamento de Salud Pública, Universidad de Barcelona, Barcelona, Spain. arlettarocio@gmail.com.|Organización Panamericana de Salud, Oficina de país Bolivia, La Paz, Bolivia. arlettarocio@gmail.com.
authors.forename: Arletta
authors.initials: A
authors.lastname: Añez
authors.affiliation: Laboratorio de control de calidad de medicamentos y toxicología del Instituto Nacional de laboratorios en Salud, CONCAMYT-INLASA, La Paz, Bolivia. molomos@yahoo.es.
authors.forename: Manuel
authors.initials: M
authors.lastname: Moscoso
authors.affiliation: Laboratorio de control de calidad de medicamentos y toxicología del Instituto Nacional de laboratorios en Salud, CONCAMYT-INLASA, La Paz, Bolivia. aplaguna@hotmail.com.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Laguna
authors.affiliation: Laboratorio de control de calidad de medicamentos y toxicología del Instituto Nacional de laboratorios en Salud, CONCAMYT-INLASA, La Paz, Bolivia. cgarnicalopez@yahoo.es.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Garnica
authors.affiliation: Laboratorio de control de calidad de medicamentos y toxicología del Instituto Nacional de laboratorios en Salud, CONCAMYT-INLASA, La Paz, Bolivia. irvime@yahoo.es.
authors.forename: Viviana
authors.initials: V
authors.lastname: Melgar
authors.affiliation: Centro de Salud Rene Salazar, Gerencia de salud Riberalta-Beni, Beni, Bolivia. maurencc@hotmail.com.
authors.forename: Mauren
authors.initials: M
authors.lastname: Cuba
authors.affiliation: Centro de Salud La Unidad, Gerencia de salud Riberalta-Beni, Beni, Bolivia. higueras_74@hotmail.com.
authors.forename: Sonia
authors.initials: S
authors.lastname: Gutierrez
authors.affiliation: Departamento de Salud Pública, Universidad de Barcelona, Institut d'Investicions Biomediques, Augusto Pi i Sunyer, Barcelona, Spain. carlosascaso@ub.edu.
authors.forename: Carlos
authors.initials: C
authors.lastname: Ascaso
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000962:Antimalarials / Q000494:pharmacology* / Q000627:therapeutic use*; D001838:Bolivia; D002648:Child; D002675:Child, Preschool; D002738:Chloroquine / Q000494:pharmacology* / Q000627:therapeutic use*; D004351:Drug Resistance; D005260:Female; D006801:Humans; D016780:Malaria, Vivax / Q000188:drug therapy* / Q000469:parasitology; D008297:Male; D008875:Middle Aged; D010966:Plasmodium vivax / Q000187:drug effects*; D017211:Treatment Failure; D055815:Young Adult
chemical_list: D000962:Antimalarials; D002738:Chloroquine