Estimate of the Rate Constant.

In the event of data available is more limited,for example,where the rate constants are at two elevated temperature or at one temperature and the heat of activation is known, it is still possible to obtain an estimate of rate constant. A lower temperature by treating the above equation using the differential form we get,


dlnk deltaHa
______ = ---------
dt RTZ

Upon integration between the limits K1 andK2 and T1 and T2 the following equatin results.


K2 deltaHa (T2-T1)
log --------- = --------- x----------
K1 2.303R T2-T1

Statistical Techniques.

There is a standard procedure available to use statistics in determining the validity of Arrhenius treatment of data.Statistical aspecys as per Cartenson and Su when the decomposition is less than 10% which is the case for many drugs of intermediate stsbility and for those new Drug Application s being considered. Zero order and First order degradations and practically indistinguishable.

Rate constants of degradation ofDiazepam Injection,

t 'o C 1000/T 105 K1(hrS-1) y=S+log K1
However. if all the data in the above format are employed.Then
logK 25'oC=[0.2257-7] + or - 0.2937
which corresponds to,
K25'0C of 8.51x10'-8 to3.30x10'-7

The interval is much narrower, and at the higher rate constant, the drug remaining after two years would be calculated to be 98.7%

Pharmacokinetic parameters

It is possible to emphasize,the relationship between pharmacokinetic parameters and physiological variables in a concrete manner rather than the use of compartmental models to define pharmacokinetic concepts.

Several forms of dosage formulations are available,perhaps the oldest examples are enteric coating of orally ingested drugs and time release often called as sustained release products. Although coating and compounding techniques can prolong the pharmacological and biological action of the drugs., their rates of release is not uniform. In other words, it is not controlled, similarly the absorption of drugs administered by parenteral route may be prolonged by repository preparation providing for therapeutic effectiveness extending from 12 hours to several days.The best example is that of Penicillin-G.

Application of physico-chemical principles.

In evaluating performance of stability studies has proved to be of considerable advantage in development of stable dosage forms.Only through this approach it is possible to accurately and adequately make use of data obtained from exaggerated storage conditions for the purpose of predicting the stability at normal shelf stability,shelf storage for extended period of time.It is extremely important that the pharmaceutical manufacturer accurately predict the shelf stability of a new product from accelerated storage data.

Introduction to Drugmonitoring.

Important field in Clinical studies and evaluation of drug both and new and old. Important methods for clinical evaluation