Diffusion of Aspirin (ASA) Based Drugs in Sodium Hydroxide Solution at Ambient Temperature.

Abstract

Diffusion is a macroscopic motion of components of a system that arises from concentration difference and plays a vital role in drug migration in the body governed by Fickian diffusion laws. This project considers effective mechanism leading to effective diffusion coefficient. The diffusion coefficient of aspirin based drugs was studied in basic NaOH of concentration range 0.01M to 0.1M and a relatively more concentrated set ranging from 0.1M to 1.0M were studied at 25oC. The study looks into the rate of diffusion of coated and non-coated aspirin drugs in aqueous NaOH solution designated different letter heads A, B, C, D, and E. The objective of this work was to determine the diffusion coefficients of aspirin drugs at different concentrations range at 25oC and to compare with those calculated from limiting ionic conductance at infinite dilution. The rate of diffusion was monitored by observing the boundary conditions of the indicator between the drug and solution. The problem statement is that there are various aspirin based drugs in the market and all have different amount of aspirin in them. The research sought to find out the rate of diffusion of the drugs and conclude if at all their values relate to their masses as per the diffusion law. In the study five (5) aspirin tablets collected from a local pharmacy in Eldoret town were used for the study. From the profile it was observed that as the time progressed the boundary increased fast for noncoated tablets compared to the coated ones. The boundary heights (x) at a time t and concentration are also recorded. The moving boundary method coefficients ranged from 2.780 x 10-6 cm2 sec-1 to 6.995 x 10-6 cm2 sec- 1, 2.196 x 10-6 cm2 sec-1 to 6.092 x 10-6 cm2 sec-1, 2.138 x 10-7 cm2 sec-1 to 6.576 x 10-7 cm2 sec-1 , 3.241 x 10-10 cm2 sec-1 to 1.617 x 10-10 cm2 sec-1 and 1.378 x 10-10 cm2 sec-1 to 2.172x 10-10 cm2 sec-1 for drugs aspirin A , B, C. D and E respectively. All the aspirin were found to give values according to Fickian mechanism. For the drug A (600mg) of aspirin the best value of diffusion coefficient of 6.995 x 10-6 cm2 sec-1 at concentrated solution and 2.780 x 10-6 cm2 sec-1 was observed at dilute range solutions while the values for coated drug E with 75 mg aspirin was found to be slightly lower. The fractional drug uptake is linear and independent of the sample of thickness when distance is plotted against time. A graph of x2 against time was plotted which was used to calculate the diffusion coefficient. The experimental values of diffusion coefficient Do were in close agreement with the expected value from infinite dilution which was a general estimation of diffusion coefficients. Quantitative data was analysed using analysis of variance and chi-square statistical. Data was presented using table and graphs. The study found that the aspirin drug with the highest diffusion coefficient is drug A. In addition, conductometric technique was recommended to give more accurate results and similar method should be constituted with the use of other techniques such as TLC and spectrophotometric method for comparison purposes with the free diffusion and it is important for manufacturers to revalidate steps in the production process, for any critical control point in the production process leads to hydrolysis of aspirin. Key words: Diffusion, Aspirin, Acetylsalicylic acid, Diffusion Coefficient, Sodium Hydroxide, Fickia