RELEASE RATE VERSUS TIME PLOTTING FOR THE RELEASE / DISSOLUTION ASSESSMENTS

Özgen COSKUN*, Ilbeyi AGABEYOGLU*°, Gül AKSOY*

* Gazi University, Faculty of Pharmacy, Department of Pharmaceutical Technology, 06330 Etiler, Ankara, TURKEY.
°Corresponding Author

Summary:
The dissolution is one of the crucial tests of solid dosage forms, namely tablets and capsules. The pharmacopeias give limits in their monographs, while a more extensive pattern can be obtained by plotting the cumulative amount dissolved/released versus time. In this basic plotting, the data points in the plot are cumulative towards the terminal phase and hence has a cumulatively increasing error in it. To offset the disadvantage of error accumulation, plotting release rates versus time seems to be a more plausible choice and rate plotting would have a pharmacokinetic meaning as well. In the assessment of the results of closed flow-through cell or paddle/basket methods, drug analysis gives the drug concentration directly, without adding the previous results. Nevertheless, these measurements are still cumulative and relative variation or fluctions appear smaller due to this fact. Plotting release rate versus time seems to be quite reasonable and advantageous. The release pattern of the dosage form can easily be followed. Whether it is a conventional dosage form with immediate release properties, or a sustained release type dosage form with prolonged release, can be seen easily. A dosage form with zero order release can also be followed clearly in this kind of plotting. The release rate and in vitro release characteristics of theophylline and pharmaceutical quality tests of the products present in the Turkish market, were specially determined and their release profiles were compared with each other in this study.

Key words:
Release rate, Dissolution, Dissolution assessment, Theophylline