Field Experiments with Chloroquine Diphosphate

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Summary and Conclusions

  1. 1.Chloroquine diphosphate in adequate dosage is completely satisfactory for the control of clinical attacks of malaria encountered in the Middle East; it is effective against P. vivax, P. falciparum and P. malariae.
  2. 2.Chloroquine diphosphate, when administered orally, is sufficiently harmless that effective doses may be given with impunity to infants and during the course of pregnancy.
  3. 3.The following therapeutic dosage schedule for chloroquine diphosphate is recommended but may be increased for massive infections:

    No. of 0.25 gm. tablets

    1–6 months4 × ¼¼¼
    7–9 months4 × ¼½½2
    10–24 months4 × ½½½3
    2–5 years4 × ½114
    6–10 year3 × 1115
    Over 10 years3 × 22210

    Therapy should be followed by weekly suppressive medication for 4–6 months where proved or latent vivax infection may exist.

  4. 4.Chloroquine diphosphate, administered at an adult dose level of 10 tablets (2.5 gm.) in three days, without follow-up with suppressive doses, yielded a vivax relapse rate of 28 per cent. When followed by fortnightly suppressive doses of 4 tablets (1.0 gm.) for 14–29 weeks, the relapse rate was reduced to 9.34 per cent, and when followed by weekly suppressive doses of 2 tablets (0.5 gm.) the relapse rate was further reduced to 5.74 per cent. Among the 21 adults in the vivax group who received an initial 10 tablet course, followed by weekly suppressive medication, no relapses occurred in seven and one-half months after the last dose. None of 53 proved cases of P. falciparum infection relapsed.
  5. 5.Chloroquine diphosphate has the combined requisites of both an effective therapeutic and prophylactic antimalarial which is safe enough to be given with a minimum of supervision throughout a malaria transmission season. By combining weekly prophylactic medication with chloroquine diphosphate (only 2 tablets per person) with adequate DDT antimosquito measures, it is possible to eradicate malaria from a community within the period of a single transmission season. In the absence of mosquito control, chloroquine diphosphate offers the means of suppressing new infections and reducing the reservoir of infection to a sub-critical threshold. Effective mass chemoprophylactic control of malaria was attained in Saideh under proved conditions of severe exposure.

Author Notes

Of the Department of Bacteriology and Parasitology, The American University of Beirut, Beirut, Lebanon, and the Chemotherapy Section of the Sterling-Winthrop Research Institute, Rensselaer, New York.