STUDIES ON THE CONTROLLED RELEASE OF ACETAMINOPHEN FROM COATED GRANULES

Acetaminophen is one of the most important non-steriodal anti-inflammatory drugs currently used in clinics. However, its short half-life and frequency of administration made it inconvenient for patients, so there is a need to search for new preparations which may be taken not more than once or twice a day. We prepared coated granules by fluidize-coating method.In in vitro dissolution study, zero order release was observed up to the time when 66% was released. After that, non-zero order release followed, when the rate decressed quickly with time. The absorption and excretion rates were determined by analysing the total amount of acetaminophen and its metabolites in the urine collected at different intervals.It was found that the apparent half-life was prolonged to 8.29 h by oral administration of the coated granules. Using the parameters, the blood concentrations were calculated at different times after oral administration of 1.1 g of coated granules. From the data, it appears reasonable to expect to keep the blood level within the effective therapeutic window of the drug for 12 h by a dose of 1.1 g of the coated granule.