Abstract
Summary
Prophylactic treatment of Trypanosoma venezuelense infections in mice may induce qualitatively different effects. Certain agents such as the diamidine of 2-phenyl-thionaphthene (98/202) and pentamidine with limited curative effect against the infection, in protected mice maintained a long parasitefree period, followed by an intermittent type of infection terminating in death. The therapeutically highly effective suramin, administered before inoculation in sufficient doses, gives a complete “true” protection against the infection; however, if the drug concentration in the host is reduced at the time of inoculation, either by diminishing dosage or by delaying the time of inoculation, the protection becomes only apparent. This “false” prophylaxis consists in a nonpatent (20-40 day) period during which parasites were not seen in the blood, followed by the intermittent parasitaemia with lethal result. In a similar group of animals, appropriate dosage schedules may produce either effect, the true or the false prophylaxis.
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