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Biomedical subjects

M D YOUNG

Publications and source records attributed to M D YOUNG.

At least 19 recordsLinked to original sources
PubMed1959

Pyrimethamine resistance in Plasmodium vivax malaria.

P. vivax infection (Korean, St Elizabeth or Chesson strain) was induced in 17 neurosyphilitic patients. Pyrimethamine in single doses of either 25, 50, 100 or 200 mg was given to test the schizontocidal and sporontocidal effects.The first single-dose treatment of 25 mg or 100 mg was given between the 8th and 61st days of parasite patency and gave moderately rapid schizontocidal and very rapid sporontocidal effects. All observed cases relapsed.The second treatment, usually three weeks or longer after the first and with the same or higher doses, had either a diminished effect or none on the schizogonous and sporogonous cycles. Subsequent treatment, even at weekly intervals, had no effect.The resistant quality was undiminished in subsequent infections transmitted by mosquito bites, by the injection of preserved sporozoites, or by transfusion of infected blood. Preserving sporozoites or erythrocytic parasites at very low temperatures did not materially affect the resistant quality.In view of the evidence presented, it appears that resistance could also occur in the field when large single doses of pyrimethamine alone are given at less than monthly intervals to febrile persons having active P. vivax infections.

Antimalarials↗
PubMed1959

The development of pyrimethamine resistance by Plasmodium falciparum.

Sixteen patent P. falciparum infections (McLendon and Panama strains) in non-immunes were treated with single doses of pyrimethamine. The schizontocidal and sporontocidal response to the initial dose was rapid.Seven blood-induced infections, of which three were treated with 100 mg and four with 50 mg, did not relapse. Of seven cases observed after 25-mg treatment, five relapsed.Delayed treatment of the relapsing infections (Panama strain) with single doses of 25 mg or 50 mg, and subsequently 100 mg, had virtually no schizontocidal or sporontocidal effect. In one case the resistant infection was transmitted by mosquitos to another patient; the subsequent infection was also highly resistant to the drug.It is concluded that under the experimental conditions of this study resistance to pyrimethamine by P. falciparum may occur rapidly after a single dose of 25 mg, being manifested during relapses on the second challenge with the drug. Increasing the drug dosage does not overcome the resistance. The resistant character is readily transmitted by mosquitos.

Antimalarials↗
PubMed1958

Chloroquine or pyrimethamine in salt as a supressive against sporozoite-induced vivax malaria (Chesson strain).

The authors present the results of a study carried out to determine the efficacy of chloroquine- and pyrimethamine-salt mixtures as a suppressive against sporozoite-induced vivax malaria (Chesson strain). The test subjects used in this study were volunteers of military age in the US Penitentiary at Atlanta, Ga. The subjects chosen were all in good physical condition and had no previous history of malaria.Both drug-salt mixtures were entirely acceptable to the volunteers, were indistinguishable in taste and appearance from ordinary salt, and remained stable under the conditions of food preparation. The weekly dosage of the drugs (300 mg of chloroquine base or 25 mg of pyrimethamine per 50 g of salt) had in each case been adjusted to the average salt consumption. Suppression of malaria was found to be complete throughout the salt-drug regimen and for 28-43 days thereafter, even though the subjects were exposed to repeated heavy doses of sporozoites. In contrast, the control subjects, exposed to the same infective doses, all exhibited parasitaemia 13-15 days after exposure.The procedures for preparing the drug-salt mixtures are described in detail and a simple method for determining the salt consumption by measurement of the urinary chloride excretion is outlined.

Animals↗