Effect of Herbal Medication on Amoxicillin Activity

Authors: Nguyen, Truc; Yost, Aubrey

Source: Journal of Dental Hygiene, 1 October 2004, vol. 78, no. 4, pp. 18-18(1)


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Purpose. This study investigated whether three herbal medicaments had any effects on amoxicillin activity.

Methods and Materials. Streptococcus mitis was the indicator microorganism. The following were placed on 10mm filter paper discs using a pipette:

The series was repeated 5 times (25 times). Plates were incubated for 24 hours at 37M-BM-:C. Zones of inhibition (mm) were measured and analyzed using the Kruskal-Wallis Ranks and Mann-Whitney U-Tests. Zones of inhibition, areas of no microbial growth, are produced on bacteria-inoculated agar whenever an antimicrobial is diffused into the medium from the paper disc. The effect of the antimicrobial is negative if no zone of inhibition develops, while a moderate or large zone indicates that the bacterium would not grow in the presence of that medication. This test is used routinely to determine clinical microbial sensitivity or resistance to many antimicrobials.

Results. The mean inhibition zone was determined for each treatment. For T1, the value was 74.40 mm (SD=6.82). T2 averaged 55.3 mm (SD=15.49), while T3 measured 60.67 mm (SD=1.84). T4 value was 73.87 (SD=6.49), and T5 measured 0 (SD=0). T1 was greater than both T2 and T3 (p=0.008), but T1 showed no significant difference from T4 (p=0.841). T2 showed no significant difference from T3 (p=0.841), and T2 and T3 was less than T4 (p=0.008). All treatments were greater than T5 (p<0.0001).

Conclusion. Results showed that echinacea extract and gingko biloba extract reduced the zone of inhibition of amoxicillin at a significant level. St. John‘s wort appeared to increase amoxicillin zone of inhibition.

Clinical Significance. It is imperative that patients disclose use of all medications and herbal supplements because antibiotic efficacy may be negatively affected.

Document Type: Abstract

Publication date: October 1, 2004

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