ORIGINAL PAPER Acceleration of in vitro dissolution studies of sustained release dosage form of theophylline and in vitro–in vivo evaluations in terms of correlations Go ¨khan Ertan • Ercu ¨ ment Karasulu • Is ¸ ıkO ¨ zgu ¨ney • Yes ¸im Karasulu • S ¸ ebnem Apaydın • Gu ¨ lten Kantarcı • Aysu Yurdasiper • Mehmet Ali Ege Received: 9 February 2011 / Accepted: 6 June 2011 / Published online: 8 July 2011 Ó Springer-Verlag France 2011 Abstract The aim of the study was to accelerate the dissolution of the sustained release dosage forms using both elevated temperature and high rpm rates. Teokap Ò SR 200 mg pellets were tested by in vitro sustained and accelerated dissolution studies using USP XXIII rotating paddle method. Sustained dissolution studies were carried out for 12 h in phosphate buffer at 37 ± 0.5°C and 50 rpm. Accelerated dissolution studies were performed for 48 min in distilled water at 90 ± 1°C and 250 rpm. The results obtained from accelerated and sustained dissolution studies were correlated using both linear and linear kinetic corre- lation methods by a computer program. While r 2 and maximum error between calculated and observed drug release rates were found to be 0.9129 and 15.9%, respec- tively, in linear correlation method, these values were observed as 0.9938 and 3.6%, respectively, in linear kinetic correlation method. In vivo plasma concentration data were obtained from six New Zealand rabbits after administration of a single dose of Teokap Ò SR 200 mg pellet. Then, the results of in vivo study were evaluated with in vitro accelerated and sustained dissolution results by applying them to in vitro–in vivo linear correlations. As a result of these correlations, it was shown that the in vitro correlation plots were very similar to the plot which was obtained by the in vivo study (f 2 = 73.81–77.11). This study suggested a way to prevent the loss of time for routine dissolution studies of sustained release preparations for quality control procedures using in vitro accelerated dissolution tests. The storage and quarantine periods of the product in process and process controls in the manufactories could be short- ened by this method. Calculation of the in vivo perfor- mance of sustained release dosage forms using the results of the accelerated dissolution studies may be counted as another advantage of the method. Keywords Theophylline  Sustained release  Accelerated release  Correlation  Similarity 1 Introduction In the last decades, numerous investigations have been conducted on sustained release dosage forms. They can achieve therapeutically effective concentrations of drug in the systemic circulation over an extended period of time, thus reducing the doses of the drugs. There are nearly 170 sustained release dosage forms used in therapy according to an electronic drug index (The internet drug index for prescription drugs 1995). Dissolution procedures of these dosage forms take generally 8–12 h. Moreover, the disso- lution period may increase to 20, 30 h for ultra-sustained G. Ertan (&)  I. O ¨ zgu ¨ney  Y. Karasulu  A. Yurdasiper  M. A. Ege Department of Pharmaceutical Technology, Faculty of Pharmacy, Ege University, Bornova, 35100 Izmir, Turkey e-mail: gokhan.ertan@ege.edu.tr E. Karasulu Department of Biopharmacy and Pharmacokinetics, Faculty of Pharmacy, Ege University, Bornova, 35100 Izmir, Turkey E. Karasulu  S ¸ . Apaydın Center for Drug R&D and Pharmacokinetic Applications, Ege University, Bornova, 35100 Izmir, Turkey G. Kantarcı Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Ege University, Bornova, 35100 Izmir, Turkey 123 Eur J Drug Metab Pharmacokinet (2011) 36:243–248 DOI 10.1007/s13318-011-0049-6