Frequency of pruritus in Plasmodium vivax malaria patients treated with chloroquine in Thailand

Chloroquine-induced itch in black-skinned African malaria patients is commo n and frequently leads to poor compliance or treatment defaulting. To asses s the frequency and severity of chloroquine-induced pruritus in an Asian po pulation, we reviewed case records of 1189 Plasmodium vivax malaria patient s treated with chloroquine (25 mg/kg over 3days) at the Bangkok Hospital fo r Tropical Diseases from 1992 through 1997. The majority of patients were T hais or ethnic Burmese (light brown skin), referred from the western border of Thailand. Overall, there were 23 patients (1.9%) with complaints of pru ritus during chloroquine therapy. Of these, 12 (52%) had palm and sole invo lvement, eight (35%) had generalized pruritus including the palms and soles , and three (13%) had palm itching only. One patient developed pruritus on the palms and soles on two consecutive admissions. The pruritus did not int erfere with daily activity, was reduced in intensity by anti-histamine ther apy, and did not affect the patient's willingness to complete the chloroqui ne regimen. Therapeutic responses in the 23 patients with chloroquine itch was similar to those without itch. Among the itch patients, there was no as sociation with gender or level of parasitaemias. Our findings indicate that the frequency of chloroquine-induced pruritus in Asian patients treated wi th chloroquine for P. vivax malaria is low in comparison with black-skinned Africans. This may be related to pharmacogenetic factors, the infective Pl asmodium species, drug metabolism or drug-parasite interactions, or a lower affinity of chloroquine for less pigmented skin.