Background and Aims: During the month of Ramadan, Moslems refrain from drinking and eating between sunrise and sunset. This review aimed to analyze the effects of Ramadan fasting on physiological and behavioral variables in healthy subjects. Methods: Articles included in this paper were taken from Medline, three international congresses on health and Ramadan, and in several cases from local journals. Results: Ramadan fasting did not dramatically affect the metabolism of lipids, carbohydrates and proteins, or the daily mean of hormonal serum levels. An increase in serum urea and uric acid was frequently reported and this could be attributed to dehydration during this month. Some changes, such as the increase of HDL and apoprotein A1, and the decrease in LDL, could be beneficial for the cardiovascular system. However, the chronobiological studies have shown that Ramadan fasting affects the circadian distribution of body temperature, cortisol, melatonin and glycemia. The amplitude of most of these rhythms decreased and the acrophase shifted. Nocturnal sleep, daytime alertness and psychomotor performance were decreased. Conclusion: The major changes during Ramadan fasting are chronobiological and behavioral. They could be responsible for the high incidence of road traffic accidents and the reduction of working hours during the month of Ramadan.

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The pharmacokinetics of Cyclosporine A (CsA) was studied in male Wistar rats weighting 300 +/- 50 g trained to a 12:12 light-dark cycle. Oral administration (40 mg/kg) was performed at 1 of 4 different temporal stages: 09.00 h, 15.00 h, 21.00 h or 03.00 h (local time) i.e. 0200, 0800, 1400 or 2000 HALO (hours after light on). Blood samples were collected over 72-96 h after dosing, plasma was separated by centrifugation at 37 degrees C and stored frozen until assay, using radioimmunoassay (RIA). Two experiments were performed: the first with 4 groups of 48 rats and a non-specific polyclonal antibody (P-RIA); and the second with only 2 groups of 48 rats and a more specific monoclonal antibody (M-RIA). Plasma concentration data were evaluated with model-based linear pharmacokinetic concepts, with apparent zero-order or first-order absorption and n-exponential disposition (n = 1, 2 or 3): models MN0 or MN1. A compartment-independent approach was also conducted and led to area under the plasma concentration-time curve (AUC) and mean residence time (MRT) determinations. A comparison of the pharmacokinetic profiles across time of administration indicates that absorption, first-pass metabolism and tissue distribution of CsA in the rat are circadian-dosing stage dependent.