Hepatitis transmission among the Sioux Indians of South Dakota.

Hepatitis A continues to occur in cyclical community-wide epidemics on the Indian reservations of South Dakota. In June 1985 a population-based serosurvey for viral hepatitis involving 120 households was conducted at the Pine Ridge and Rosebud Sioux Indian reservations in South Dakota. The serosurvey was performed shortly after a large hepatitis A epidemic on the Pine Ridge reservation in 1983-84, and immediately before a large hepatitis A epidemic on the Rosebud reservation in 1985-86. The overall seroprevalence for antibodies to hepatitis A virus (anti-HAV) was 76.2 percent (Pine Ridge reservation 80.5 percent, Rosebud reservation 72.0 percent, relative risk = 1.12, 95 percent confidence interval = 1.01, 1.24). For age groups 0 to 4 years, 54.2 percent and 36.1 percent of children were seropositive at Pine Ridge and Rosebud, respectively. Seropositivity rose rapidly with age; by age 40, more than 90 percent of persons at both Pine Ridge and Rosebud were anti-HAV positive. Only 1.1 percent of persons tested were positive for hepatitis B markers. Anti-HAV seroprevalence rates in both communities are similar to rates observed in developing countries. The surprisingly high anti-HAV seroprevalence among young children at Rosebud, where clinical hepatitis A had been virtually absent in the previous seven years, indicates that high-grade silent transmission was taking place during the interepidemic period.

Phenytoin metabolism in subjects with long and short plasma half-lives.

Normal adult men with long and short phenytoin plasma half-lives were given 300-mg oral doses of phenytoin once daily for 15 days. Plasma levels of phenytoin (DPH) and its major metabolite (p-HPPH) were measured during the period of drug administration and for 5 days thereafter. Average steady-state plasma levels of DPH rose to 13.4 micrograms/ml in the long half-life group, compared with 3.6 micrograms/ml in the short half-life group. HPPH levels in the long half-life group were about one half of those observed in the short half-life group. The DPH/HPPH ratios in plasma specimens showed excellent correlation with the plasma half-lives of DPH and average steady-state levels, suggesting that this ratio could provide guidance in the selection of optimum dosage regimens for problem patients.

Simplified fluorometric assay for diphenylhydantoin in plasma.

The fluorometric benzophenone procedure for diphenylhydantoin has been simplified by eliminating the need for preliminary extraction of plasma with an organic solvent. Assays are done directly on 0.2 ml of plasma by treating it with alkaline permanganate to form benzophenone, extracting the benzophenone with heptane, and then shaking the heptane layer with sulfuric acid and measuring the fluorescence of the acid layer. The assay is highly reproducible, and adequately sensitive to detect 1 mug of the drug per milliliter of plasma. Fluorometric and gas-liquid chromatographic assays of 154 plasmas gave results that were not significantly different, even in the presence of phenobarbital, other barbiturates and anticonvulsant drugs, or of various tranquilizers and other commonly used drugs. The assay is rapid, the unit cost per assay low.