**13.2. Screening of putative drug molecules**

Selection of molecules for further study is usually conducted in animal models of human disease and the pharmacological tests include both the *in vitro* and *in vivo* studies after the initial screening for biological activity. For instance, antibacterial activity of drugs is assessed by their ability to inhibit growth of a variety of micro-organisms, while hypoglycemic drugs are tested for their ability to lower blood pressure.

The *in vitro* methods include incubation of a parent compound with various subcellular fractions such as microsomes, individual recombinant drug metabolizing enzymes from cells or tissue slices. The *in vivo* studies involve working on typical animal models such as dogs or rats. Some of the *invitro* and *invivo* studies that may be performed are shown in tables 1 and 2 below;


**Table 1.** Screening of drugs for specific inhibitory effects on enzymes and isolated tissues.


**Table 2.** Putative animal models used in studying effects of drugs

If an agent possesses useful activity it would be further studied for possible adverse effects on other major organs. These studies might suggest the need for further chemical modification to achieve desirable pharmacokinetic/pharmacodynamic properties.
