Stability of aspirin in aspirin-containing formulations
Loading...
Date
2005-11-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Ten brands of aspirin-Containing formulations were analyzed for the stability of aspirin in the formulations. Two (2) brands were Aspirin-only formulations, six (6) were aspirin- caffeine, and the last two (2) were aspirin, paracetamol arid caffeine.
The aspirin content of the aspirin-only formulations complied with BP requirements.
Percentage contents of aspirin in the aspirin-caffeine combinations using the BP method were all below the acceptable range. Modifying the refluxing time from 30 minutes to 60 minutes phenomenally changed the results, making all of them pass the test. The variation in the results from the BP method (30 minutes reflux) and the modified BP method (60 minutes reflux) was found to be statistically significant.
However, the results obtained after refluxing for 60 minutes were statistically proven not to differ significantly from an extractive method for analyzing aspirin in combination products.
The aspirin content of the aspirin-paracetamol-caffeine formulations also complied with BP requirements.
Since aspirin breaks down readily to form salicylic acid and acetic acid in moist air, salicylic acid was used as the basis of determining instability of the aspirin.
A quantitative method of analyzing the levels of free salicylic acid in these formulations was developed using a spectrophotometric approach. A complex formed between ferric ions (from ferric ammonium sulphate) and salicylic acid has an absorbance at 540nm. The absorbance was directly proportional to the concentration of the salicylic acid present.
This method was used to determine the levels of salicylic acid in the ten (10) brands being investigated. Both aspirin-only formulations failed the test by having 1 .45% and 1.86% of salicylic acid instead of the allowable limit of 0.6%. For the other brands containing caffeine and/or paracetamol, the allowable limit of free salicylic acid is 3%. Two of the brands failed the test with levels of 3.25% and 3.02%. The others passed the test.
Considering the fact that most of the products were freshly manufactured, it was clear that aspirin needs to be handled and stored well in order to safeguard it from instability problems.
The presence of paracetamol and caffeine appear not to augment the instability problem of aspirin.
Description
A Thesis submitted to the Department of Pharmaceutical Chemistry, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Science, 2005