Amoxicillin is a semi-synthetic penicillin, derived from 6 APA (6-penicillinic acid). It is a slightly acid compound, slightly fat-soluble, stable in acid medium and can be administered by enteral or parenteral route.

Amoxicillin is a broad spectrum antibiotic with a bactericide effect primarily towards sensitive microorganisms. It causes deteriorations to the bacterial cell wall, leading to osmotic lysis of the cell.

Streptococcus suis are usually susceptible to amoxicillin (MIC < 0.5 µg/ml).

MIC90 for Streptococcus suis

After oral administration in feed, amoxicillin bioavailability is approximately 30%. The fraction reaching the blood stream is metabolized to a slight extent. The metabolite identified in laboratory species is penicilloic acid that is rapidly eliminated in the urine. Amoxicillin is weakly bound to plasma proteins (about 20%) and is widely distributed in different organs.

After single oral administration of the product at dose level of 20mg/kg in pigs, mean Cmax corresponded to 2.93µg/mL, therefore almost 6 times the critical breakpoint for amoxicillin resistance in S. suis. The mean Tmax corresponded to 1.8 hour. The time when amoxicillin mean plasma concentrations were above the critical MIC (0.5µg/mL) was 6 hours, i.e., 25% of the dosing interval.
Twelve hours after treatment, mean amoxicillin concentration was 0.159 µg/mL, i.e., still above the MIC90 values against S. suis (0.015µg/mL) observed in 2007-2008.