We have given single high doses of dexamethasone phosphate by intravenous infusion as an antiemetic to 15 cancer patients receiving regimens containing cisplatin and/or doxorubicin. The patients received graded doses of dexamethasone phosphate, in the range 40-200 mg, dependent upon nausea and vomiting scores, during up to three consecutive cycles of cancer chemotherapy. Plasma and urine concentrations of dexamethasone (dexamethasone alcohol) were measured by HPLC. The plasma concentration - time data were described by an open two-compartment model. The pharmacokinetic variables were independent of the dose of dexamethasone over the range studied. The terminal half-time was 4.0 +/- 0.4 h and the total body clearance was 3.5 +/- 0.4 ml X min-1 X kg-1. The volume of the central compartment and the total apparent volume of distribution were 0.23 +/- 0.03 and 1.0 +/- 0.1 l X kg-1 respectively. Approximately 8% of the dose was excreted into the urine as dexamethasone.
The antiemetic effect of graded, single high-dose intravenous dexamethasone was studied in 27 patients receiving combination chemotherapy with either doxorubicin (50 mg/m2) or cis-platinum (100 mg/m2). A total of 57 cycles were individually evaluated, utilizing a detailed rating system. Nausea and vomiting did not occur in 20 of 57 cycles; in 17, the chemotherapy was doxorubicin-based, and in 3 it was cis-platinum-based. Of the 37 cycles associated with nausea and vomiting, 32 contained Cis-platinum and 5 doxorubicin. The average dexamethasone dosages for doxorubicin and platinum-containing combinations were 40 and 95 mg/m2, respectively. Side effects included a dose-dependent sensation of perineal pruritis (11 patients, 17 cycles) lasting for serveral minutes, and subjective feelings of increased appetite and well-being. Dexamethasone administered intravenously 15 min prior to chemotherapy in a dose of 40 mg/m2 apparently provides highly effective antiemetic protection for patients receiving treatment cycles containing doxorubicin; however, for patients receiving regimens containing cis-platinum, the antiemetic effect of dexamethasone as a single agent is limited.
The genetic basis of pheromone titre in the pink bollworm moth, Pectinophora gossypiella (Saunders), was examined through artificial selection for females that produce greater amounts of the sex pheromone [a mixture of (Z,E)and (Z,Z)-7,ll-hexadecadienyl acetates]. Mean (+SD) pheromone titre increased by 91%, from 24.0k8.1 to 45.8k7.9 ng per female, in six generations of selection. No change in component ratio was observed within the selected line. The duration of male wing fanning, measured in a still-air bioassay, did not change in the femaleselected line.
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