The production of spheres loaded with acetaminophen by the cross linking technique was achieved.The hydrophilic polymer sodium alginate which gels in presence of a cross linking ion was used as a matrix for the spheres production. Two processing variables were studied. The drug load in the formula which varied from 5% w/v to 20% w/v, and the cross linking agents used; calcium chloride, calcium acetate, and aluminum sulfate. Also the effects of the dissolution medium and the rotational speed of the dissolution apparatus on drug release were investigated. Spheres were compacted into 4 5 0 mg tablets without the aid of excipients. The drug release from spheres containing 20% w/v drug was 90% after 6 hours, while the drug release from compacts of these spheres was 90% after 12 hours. The mechanism of drug release from spheres and compacts containing 20% w/v drug and prepared with 5% w/v cross linking material

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The aim of this work was to study the pharmacokinetic behaviour and the inhibitory effect on acetylcholinesterase and butyrylcholinesterase activities of chlorpyrifos in male and female cattle after pour-on administration. Determination of cholinesterase activity in plasma and erythrocyte was carried out according to Ellman kinetic method. The mean baseline activities were 9338.39 +/- 1331.61 and 13220.69 +/- 2274.18 to acetylcholinesterase and 624.65 +/- 39.32 and 641.68 +/- 88.08 IU/L to butyrylcholinesterase in females and males, respectively. Acetylcholinesterase was the predominant form of cholinesterase analyzed, with low levels of butyrylcholinesterase. The basal acetylcholinesterase activities of the bulls were significantly greater than those of cows. The inhibitory effect of topical chlorpyrifos administration was lower on butyrylcholinesterase than on acetylcholinesterase. Chlorpyrifos peak plasma concentration (male:10.920 +/- 4.18; female:12.12 +/- 3.88 microg/L) were reached at 11.92 +/- 9.19 and 8.17 +/- 7.67 h in male and female, respectively. The values of area under curve were 185.96 +/- 168.45 and 278.89 +/- 270.00 microg h/L and mean residence time were 13.95 +/- 8.10 and 14.90 +/- 9.80 h in male and female, respectively.

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