Bioavailability And Pharmacokinetic Studies Of Brands Of Paracetamol Dosage Forms

Total drug content for thirteen differentbrands of paracetamol tablets and five brands ofparacetamol syrup has been evaluated.Chemical assay methods based on colorimetricand spectrophotometric absorption were employed inthe study. The results (except for one brand ofparacetamol syrup) complied favourably with thestated amount in the monogram for paracetamolcontent (95.0 - (5.0)%. The exceptionalparacetamol syrup (S2) was found to contain 89.12%of the labelled amount of paracetamol.Dissolution rate profile of thirteen differentlots of paracetamol tablets in 0. 1M HC1 solutionwas investigated by means of U.S.P. XVIII rotatingbasket method. The drugs showed some similaritiesas well as some differences in their respectivedissolution rate profiles. The differencesobserved in the dissolution rates of the drugswere probably due to the different manufacturingprocesses employed by the different manufacturers.Disintegration time test was carried out onthree brands of paracetamol tablets (Al, A2 andA7) . There was considerable variation in theirdisintegration times which could be due todifferent types and amount of disintegrant used bythe different manufacturers.In vivo bioavailability study of some brandsof paracetamol tablets was carried out in healthyhuman subjects. A simple, reliable and rapidmethod of paracetamol estimation, developed byGlynn and Kendal (1975), was adapted for thedetermination of serum and saliva paracetamollevels. Serum and saliva paracetamol half-liveswere calculated by the method of residuals. Areaunder the concentretion-time curve wascalculated by the trapezoidal rule andextrapolation to infinity.Higher but statistically insignificant, levelsof paracetamol were detected in saliva comparedwith the serum for the first 60 minutes followingoral ingestion of lg of the drug. There was a goodlinear correlation between the concentration ofparacetamol in serum and saliva. One of theproducts (A7) was verv slowly absorbed, consistentwith its low dissolution rate found in vitro.Paracetamol elimination half-lives calculated forserum and saliva were similar.The in vivo data quantitatively correlatedwith the in vitro release of these tablets.

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