Chronobiologic Considerations in Pharmacologic and Toxicologic Studies: Fact or Fancy

Timed treatment of the arthritic diseases: a review and hypothesis

Evidence has been accumulating regarding the importance of biological rhythms in the diagnosis and treatment of a variety of diseases and disorders. Increasingly, the arthritides have shown statistically quantifiable rhythmic parameters. Included in the latter group are joint pain and joint size. In addition, a number of drugs used to treat rheumatic diseases have varying therapeutic and toxic effects based on the time of day of administration. Among these drug classes are nonsteroidal antiinflammatory drugs, glucocorticoids, and a number of cytostatic agents. In the last group of agents, experience in treating malignant disease suggests that time-specified treatment may reduce the toxic effects of low-dose cytostatic treatment of rheumatoid arthritis (RA) and related diseases. This article reviews that evidence and suggests a rationale for the timed treatment of RA with methotrexate.

Circadian rhythm of the liver of male rats pre-treated with phenobarbital--II. Hexobarbital sleeping time and lipids content in liver and serum

The circadian rhythm of hexobarbital sleeping time and lipids content in liver and serum were studied in 226 male Sprague-Dawley rats pretreated daily at 0800-0900 with 70 mg/kg (study 1 or 3) or 50 mg/kg (study 2) phenobarbital (PB) orally for 7 days. Thereafter, eight (study 1) or five (study 2 and 3) rats each were studied at 4-hr intervals at 1000, 1400, 1800, 2200, 0200, 0600 and 1000 through the following day. The lighting schedule in the colony was 12:12 +/- light:dark (light from 0600 to 1800). The hexobarbital sleeping times of PB-pretreated rats were generally shortened compared to the controls and no circadian rhythm was observed. PB-treatment increased slightly the liver content of cholesterol, and significantly that of triglycerides and phospholipids. Liver cholesterol and phospholipids showed circadian rhythms with peaks during the dark phase. No circadian rhythm of liver triglycerides existed. In serum, levels of triglycerides and phospholipids were slightly lowered by PB-treatment, while levels of cholesterol and beta-lipoprotein were not influenced. Serum values did not exhibit circadian rhythms.