EFFECT OF POTASSIUM CARBONATE AND VISCOSITY GRADE OF HYDROXYPROPYLMETHYLCELLULOSE ON THE BIOAVAILABILITY OF FUROSEMIDE FROM PRESS-COATED PROLONGED-RELEASE TABLETS

This study concerns press-coated modified-release tablets in which bot h the core and the coat contain a drug (furosemide) but only the coat contains a polymer (hydroxypropylmethylcellulose) to control drug rele ase. The drug release profile from this kind of tablet is biphasic: a slower initial phase is followed by a clear increase in the release ra te. The main aim was to study the scope for systematic modification of the release rate of furosemide using the alkalizing agent, potassium carbonate. It is concluded that the addition of potassium carbonate is necessary for adequate release and absorption of furosemide from the press-coated tablets described. The optimum amount of potassium carbon ate was that chemically equivalent to the amount of furosemide in the tablet. This conclusion is based on in vitro dissolution studies and o n bioavailability studies in dogs. The polymer in the coat also affect ed the drug release profile and absorption parameters.