Drug discovery and development is a vigorous process that hops with the recent advances in pharmaceutical field, which requires understanding of pharmacokinetic, pharmacodynamics, pharmacogenomic profile of the drug. Development of new drugs is of prodigious importance for many clinical conditions but rising cost of drug development leads to decrease in number of drugs getting marketing approval. Additionally, drug development is a long, complex and expensive procedure.

One important aspect of a drug development is to study its pharmacokinetic profile. Wretched pharmacokinetic profile is itemised to be a biggest reason for failures during drug development. Too low concentrations of drug at the target organ for lesser time can lead to efficacy failures, while wrong concentrations reaching wrong targets for longer time may lead to toxicity. Thus, a new experimental methodology has been developed, known as Phase 0 or micro dosing studies, to address concerns related to drug metabolism and pharmacokinetics.

Micro dosing is a technique for studying the behaviour of drugs in humans through the administration of doses so low ("sub-therapeutic") they are unlikely to produce whole-body effects, but high enough to allow the cellular response to be studied. This is called a "Phase 0 study" and is usually conducted before clinical Phase I to predict whether a drug is viable for the next phase of testing. Human micro dosing aims to reduce the resources spent on non-viable drugs and the amount of testing done on animals.

A new method using big physics instrumentation to obtain human pharmacokinetic information before the usual expensive phase I safety program is accompanied is the phase 0 micro dosing. It is anticipated that micro dosing will help to lessen or substitute the extensive animal testing of compounds for kinetics, which may later be rejected in human studies. Therefore, micro dose studies use small quantities of drug, which is not envisioned to produce any pharmacologic effect, when administered to humans, and, hence, may not cause any adverse events also, but may produce useful pharmacokinetic information and help in development of the new compound.

The changes observed in the regulatory guidelines also encourage the frequent use of micro dosing in human subjects. Although regulatory authorities may not make micro dosing a mandatory requirement as the data can be obtained by other methods as well, the regulatory agencies may provide approval for micro dosing or analogous initiatives for companies bringing life-saving drugs to the development and commercialization phases speedily.

Micro dosing requires minute quantities of the drug for safety testing. It is so small that when administered to human subjects, it does not produce any pharmacologic effect; hence, the risk of adverse events is negligible. An added advantage of micro dosing is fewer animal studies are required before Phase I clinical trials. Consequently, further animal studies can be avoided with compounds having incongruous pharmacokinetic profiles.

A study performed to compare the pharmacokinetics of five drugs – warfarin, ZK253, diazepam, midazolam and erythromycin, administered at a micro dose or pharmacological dose, it is concluded that micro dosing offers the potential to aid in early candidate selection. Furthermore, the cost of conducting a micro dose study is remarkably less, as compared to a full Phase I study. Micro dosing could be useful in the discovery of endogenous biomarkers, which would assist in the quantitative evaluation of the in vivo effects of drugs.

Micro dosing would help both patients and the pharmaceutical industry with earlier availability of new drug. Micro dosing allows not only selection of drug candidates more likely to be developed successfully, but also helps in determination of the first dose for the subsequent Phase I clinical studies.