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Background: Stability of drugs depends on both environmental factors and drug-related factors. Exposure of medicines to high temperatures during storage or transit could reduce their efficacy thus, shelf life and expiry dates may no longer be guaranteed. The objective of this study was to determine the effect of heat and environmental conditions on the antimicrobial efficacy of amoxicillin trihydrate.
Methods: Five brands of amoxicillin trihydrate capsules and six brands of amoxicillin trihydrate powder for suspension were purchased from retail pharmacies in Abuja, Nigeria. For the capsules, 100 μg/mL of the different brands and 25, 50 and 100 μg/mL of reference standard were prepared and subjected to heat treatment at different temperatures (25, 40, 60 and 80 oC) for 30 min. Each of the amoxicillin trihydrate powder for suspension was reconstituted in water and subjected to different storage conditions for 7 days. The UV absorbance of the reference amoxicillin trihydrate was determined while the potencies of heat-treated amoxicillin capsules and stored suspensions were evaluated by agar diffusion method.
Results: At 25 and 40 oC there was no signifificant change in the antimicrobial efficacy of amoxicillin, however as the temperature increased to 80 oC there was a reduction in the zones of inhibition against the test organisms. The absorbance readings of the heat-treated reference amoxicillin trihydrate powder gradually increased with increase in temperature. There was no significant (p< 0.05) reduction in the antimicrobial effffects of the reconstituted suspensions within 7 days of testing.
Conclusion:The antimicrobial stability of amoxicillin can be affected by exposure to extreme heat
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