A 50:50% w/w combination of HPC HF and HPC EXF formed a tougher gel-like structure upon contact with the dissolution medium.
Because tablets containing Avicel PH 101 as a filler were hydrophobic, they required more time to hydrate upon contact with
the dissolution medium to diffuse out salbutamol sulfate from the gell-like structure of the outer shell. The hydration and
disintegrant properties of Starlac present in the core tablet resulted in a rapid drug release and a slower lag time compared
with the formulation containing Avicel PH 101 as filler. The pressure generated upon the swelling of Ac-Di-Sol with Avicel
PH 101 as filler was not sufficient to break the outer shell because of the tough gel-like structure formed on the outer shell.
Obviously, the erosion of the outer-coating shell of the core tablet containing Starlac was lower than when Avicel PH 101
was used as as filler (see Figure 9).
A photograph of the formulation containing 50:50% w/w HPC HF to HPC EXF at the 20th hour also suggests the proper hydration
effect of the core and shows the possible mechanism of release of salbutamol sulfate from this formulation (see Figure 10).
Formulation containing a higher weight ratio of HPC HF to HPC EXF showed more delay in the release of salbutamol sulfate and
an increase in the time lag to start the release of salbutamol sulfate.
Various drug-release mechanisms were observed by incorporating different polymers into the outer shell and different core
compositions. By deepening the knowledge of polymeric materials' behavior in dosage forms and, in particular, their application
in the press-coating of different core compositions such as those proposed in this study, a safe and more accurate targeting
of the drug from dosage forms can be achieved.
Shilpa P. Chaudhari and Praveen D. Chaudhari* are professors of pharmaceutics at Padm. Dr. D.Y. Patil Institute of Pharmaceutical Sciences and Research, Pune University,
India, tel. +91 9850179873, fax +91 22 27421097, firstname.lastname@example.org
Chetan J. Mistry is a research scientist at the Torrent Research Centre, India. Manohar J. Patil, PhD, is head of the Department of Pharmacognosy at Padm. Dr. D.Y. Patil Institute of Pharmaceutical Sciences and Research. Nilesh S. Barhate is a research and development officer at Blue Cross Laboratories, India.
*To whom all correspondence should be addressed.
Submitted: Sept. 26, 2006. Accepted: Oct. 11, 2006.
Keywords: controlled release, coating, excipients, direct compression, formulation, solid dosage forms, tableting