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Introduction

DISSOLUTION TESTING OF TABLETS & CAPSULES Practical 4 INTRODUCTION Dissolution involves the relocation of a solute molecule from an environment where it is surrounded by identical molecules (with which it forms intermolecular attractions) into a liquid where it is surrounded by non-identical molecules. Optimal drug dissolution is crucial to the success of oral drug therapy. Slow dissolution can be correlated with poor performance of oral dosage in vivo, and drugs of low aqueous solubility provide a major challenge during the design of oral dosage forms. Solid oral dosage forms need to be in solution before absorption occurs; dissolution is often the rate limiting step in absorption of a drug and can control the overall bioavailability of the drug. Dissolution is important for the bioavailability of oral solid dosage . The rate of drug dissolution of solids can be described using the Noyes-Whitney equation. Dm/dt = DA ( Cs - C) h Dm/dt = rate of drug dissolution at time t, D = the diffusion rate constant A= surface area of particle Cs =Concentration of drug in the stagnant layer C=Concentration of drug in the bulk solvent h = thickness of the stagnant layer. dC/dt is the rate of drug dissolved per time expressed as concentration change in the dissolution fliud. The Noyes-Whitney equation shows how factors such as solubility and surface area can affect dissolution rate. Dissolution rates may be increased by decreasing the drug particle size (this increases the available surface area to the dissolveing fluid), increasing solubility in the diffusion layer (the ionised form of the drug will have greater solubility in the diffusion layer than the unionised weak acid or weak base), and altering the pH of dissolution medium. ...read more.

Middle

mg % mg % mg % 5 6.98 27.9 2.025 8.1 4.5 18.01 10 12.6 112.5 31.5* 126 22.05 88.2 15 25.65 102.6 19.8 79.2 22.73 90.9 20 20.25 81 22.5 90 21.38 85.5 25 2.25 9 38.25 153 20.25 81 30 36.9 147.6 58.5* 234 47.7 190.8 35 29.7 118.8 56.5 226 43.1 172.4 40 29.7 118.8 28.13 112.5 28.92 115.7 45 26.1 104.4 26.1 104.4 COMMERCIAL FORMULATIONS TESTED * Panadol actifast ( vessel 1 and 2) * Anadin ( vessels 3 and 4) * Paracetamol galpharm(vessel 5 and 6) Vessel number 1 2 3 4 5 6 Time min Absorbance 5 0.841 0.751 1.155 1.144 1.324 0.571 10 1.510 1.531 1.580 1.579 1.451 0.932 15 1.572 1.623 1.677 1.391 1.526 1.173 20 1.722 1.611 1.608 1.559 1.479 1.335 25 1.630 1.646 1.456 1.581 1.536 1.390 30 1.365 1.555 1.628 1.598 1.482 35 1.662 1.516 1.618 1.479 40 1.362 1.499 1.523 1.432 45 1.289 1.436 50 55 60 For tablets, all solution has been diluted by 20 fold. To calculate the concentration, in 0.9L the concentration is read of the calibration curve; example 0.841 read off the graph is 15.45 mg/L. This is then multiplied by 20 (dilution factor). 15.45 x 20= 345mg/L : in 0.9L; 0.9 x 345= 310.5mg. Vessel number 1 2 3 4 5 6 Time min Amount(mg) 5 310.5 256.5 441 436.5 504 211.5 10 580.5 594 607.5 607.5 562.5 438.89 15 621 630 657 535.5 594 454.5 20 657 621 621 576 576 513.9 25 639 643.5 562.5 612 598.5 535.5 30 517.5 576 639 616.5 562.5 35 657 585 630 558 40 517.5 576 585 556.2 45 490.5 558 The expected normal weight is 500mg: To calculate % of drug released in solution, is the amount weighed in solution divided by expected weight multiplied by 100%. ...read more.

Conclusion

CONCLUSION The results obtained enable the conclusion that paracetamol capsules containing the diluent lactose undergoes faster dissolution in comparison to formulations containing starch 1500 and microcrystalline cellulose, where microcrystalline cellulose formulations was the slowest dissolution. Additionally, the commercial paracetamol formulations results enable the conclusion that Panadol Actifast Tablets and anadin undergo faster dissolution with higher percentage of drug released compared to that of galpharm hence are more convenient when fast relief of pain is required. Furthermore, it also enables the conclusion that the more expensive the product the better its quality, as it contains more excipients that could potentially aid the dissolution of the formulation, improve mecahanical strength and flavouring and also appearance of product. Percentage of drug content released into solution was greater than 100 prior to obtaining a mean value, but this would indicate that more drug is being released into solution than there actually is available to be released. Also an explanation, behind this is that perhaps the actual drug content in the formulation is more than that stated or that there is some other excipient in the formulation that absorbs UV light in the same wavelength range as paracetamol, causing interference in the reading thus giving higher values. A possible way to avoid this problem in future would be to use a more reliable method to assess the concentration. From the practical it is difficult to conclude whether tablets dissolve in solution faster than capsules, as the excipients present in the formulations weren't entirely the same. In future this practical could be further improved by formulating capsules containing the same ingredients as a tablet and then testing their dissolution to see whether differences in dosage form influence the dissolution rate. Also the entire procedure in conducting experiment is not reliable as in using the syringe to take out the solution this was not taking out the accurate volumes. ...read more.

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