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Ivan, Your assumption is pretty much correct. A half life of a drug is the time it takes for the drug to reach half the blood level that it reaches at its peak (not the maximum effect). It may or may not correlate with drug effectiveness (but usually does). An article follows: Authors: Buclin T , Biollaz J Departement de Medecine, Centre Hospitalier Universitaire Vaudois, Lausanne. Schweiz Rundsch Med Prax 1997 Oct 22;86(43):1693-7 Article Number: UI98045271 Abstract: Among the pharmacokinetic concepts, the elimination half-life is most frequently used to describe the fate of a drug in the organism. The fact is often neglected, that the half-life depends on various physiological processes (organ clearances, distribution, occasionally absorption or binding to macromolecules). In many situations, the half-life has little to do with the duration of the effect which may depend on effective concentrations, equilibration delays at site of action, indirect response mechanisms, tolerance, or appearance of active metabolites. Finally, the half-life represents an ambiguous criterion for the choice of drugs: short (or long) half-life can be considered either advantageous or disadvantageous, according to endpoints selected. Ivan M Suzman wrote: > On Sun, 12 Sep 1999 20:01:32 -0700 "J. R. Bruman" <[log in to unmask]> > writes: > > "Because cabergoline seems to have much fewer nasty side effects than > bromocriptine, and especially since its half-life of 65 hours permits > Parkinson's sufferers to sleep all night through," > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > ^^^^^^^^^^^^^^^^^^^^ > Hi from Maine to J.R., Brian, and everyone- > > Can we please come to a consensus about the meaning of the term, > "half-life" ? Knowing what a half-life is could be of IMMENSE help in > planning our daily medicaiton routines! > > I understand it to mean the usual time that elapses from the point that a > > medication takes effect, until that at which half of the medication has > been used up. Am I close? > > Is this purely based on chem-lab analysis, or also on REAL human > beings whose responses to a drug are closely monitored? > > What are thought to be the half-lives of some of the more convential > PD drugs, like sinemet, madopar, sinemet CR, and selegeline? > > Best regards, > > Ivan > > ^^^^^^ WARM GREETINGS FROM ^^^^^^^^^^^^ :-) > Ivan Suzman 49/39/36 [log in to unmask] :-) > Portland, Maine land of lighthouses 60 deg. F :-) > ******************************************************************** -- ****************************************************************************************** Charles T. Meyer, M.D. Middleton (Madison), Wisconsin [log in to unmask] ******************************************************************************************