Bioavailability is a term used to indicate measurement of both, the relative amount of and administered drug that reaches the general circulation and the rate at which this occurs. Assessment of bioavailability indeally requires specific and sensitive methods for determination of drug concentrations in human body fluids. For the purposes of most bioavailability studies, it is sufficient to determine four indexes: maximum drug serum concentrations (Cmax), time of maximum drug concentration (tCmax) area under the drug serum half life of the drug. Potential drugs interactions and the effect of the disease state must also be evaluated, to adjust drug dosage in order to obtain an optimal therapeutic effect with minimal unwanted side effects.