Abstract:
Extended release drugs formulations are intended to continuously
release medication over a prolonged period, after a single dose. Drugs which
have a narrow therapeutic window and a moderate half life are good
candidates for such formulations. One approach to such formulations is to
embed the drug in a matrix which 'would act as a release retardant. We
describe here our studies on the formulations of an extended release
theophylline tablet using polymer matrices.
Different acrylate copolymers sold in the market under the "Eudragit"
label were subjected to experiment. Microcrystalline cellulose and calcium
sulphate dihydrate were used as filler excepients. The theophylline release
patterns of the different formulations were studied, at 37aC in phosplate
buffers. The theophylline concentration were measured by Ul/ absorption
spectroscopy A careful study of the release patterns of different formulations
let to a formulation using Eudragit=E RSPO, a trimenthylammonioethyl
methacrylate copolymer and calcium sulphate dihydrate, which conformed
with the following release pattern in accordance with USP 25.
Time (hours) % Drug Released
1 10 - 30
2 30 - 55
4 55 - 80
8 >80
This formulations 'was used to prepare tablets with two dosages, paediatric
dose (125 mg) and adult dose (250 mg). The adult dose was subjected to a
bioequivalence study against an established commercially available slow
release 250 mg formulation (Neulin 250 SR, 3M Pharmaceuticals, Australia)
Twenty healthy male volunteers participated in the study. Theophylline
concentrations in serum were determined by Fluorescence Polarization
Immunoassay. There was no significant difference between the two
formulations in basic bio availability and pharmacokinetic parameters
(AUC CiliaIa'nd Tlllal
The new Theophylline ER 125 mgformulation developed is nOH'being
manufactured by the State Pharmaceutical Manufacturing Corporation
(SPMC).
a. State Pharmaceutical Manufacturing Corporation, Sri Johne
Kothalawala Estate, Ratmalana, Sri Lanka 071-1815117
b. Dean Faculty 0.( Natural Science, University of Sri Jayawrdanapura,
Nugegoda
c. Pharmacology Division, Faculty of Medicine, University of Sri
Jayawrdanapura, Nugegoda.
