Behaviour modification drugs

A survey by this author of the 1 October 2000 release of the CSD ( 225 000 entries) yielded 6353 hits for the qualifier form , 1045 hits for the qualifier phase 528 hits for the qualifier polymorph , 201 hits for the qualifier modification , 28 342 hits for the qualifier solvate and21 132 hits for the qualifier hydrate . Of course, the last two numbers give no indication of whether the materials are polymorphic and none of these statistics indicate the instances for which the structures of more than one form have been determined. The data for hydrates and solvates from the CSD may be considered quite reliable, since molecules of solvation are usually positively identified in the course of a crystai structure determination. The frequency of polymorphs, however, is likely to be underestimated, since many crystal structures of polymorphic systems, or what later are discovered to be polymorphic systems, are reported without making note of that fact. If the structure of only one member of a polymorphic family has been reported, then there may not be any reference to the polymorphism in the CSD. References to drugs discovered prior to 1971 that form solvates have been compiled, along with a separate summary of the thermomicroscopic behaviour of drug hydrates by Byrn et al. (1999). 

Next, some typical examples will be presented of how a DNA-electrochemical biosensor is appropriate to investigate the DNA damage caused by different types of substances, such as the antioxidant agent quercetin (Scheme 20.1), an anticancer drug adriamycin (Scheme 20.2) and nitric oxide. In all cases, the dsDNA damage is detected by changes in the electrochemical behaviour of the immobilized dsDNA, specifically through modifications of the purinic base oxidation peak current [3,5,40]. 

Many drugs can be obtained in different polymorphic modifications. These forms may possess fundamentally different properties, for instance different rates of assimilation because of differences in solubility [12]. The enormous economic implications of this aspect are witnessed, interalia, by the number of patent litigations involving drug companies. Polymorphs may also show different behaviour under mechanical stress, with relevant consequences on comminution and tableting, hence on their processing and marketing [13]. 

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