**3.1. Amoxicillin as the antibiotic of choice for prophylaxis**

The standard regimens of the three guidelines mentioned above recommend the oral administration of 2 g of amoxicillin between 30 and 60 min before a dental procedure in adults. In the case of children, the recommended dose is 50 mg/kg body weight. When oral administration is not possible, amoxicillin can be administered intramuscularly or intravenously at the same dose.

Amoxicillin was introduced into the IE prophylaxis protocols in 1982 [4] and since that time it has become the drug of choice in the prophylactic guidelines internationally. From a pharmacological point of view, amoxicillin has optimal characteristics due to its rapid absorption after administration by mouth, achieving maximum plasma concentrations within 1–2 h after ingestion, and therapeutic levels are maintained for a minimum of 6 h. Amoxicillin is highly active against streptococci and also covers anaerobes and gram-negative bacteria. It is thus effective against the majority of microorganisms present in bacteraemia of oral origin. However, it is considered that between 5 and 35% of the microorganisms detected in blood cultures from patients undergoing dental treatment can be resistant to the antibiotic. This finding, together with the increased prevalence of IE caused by penicillin-resistant staphylococci and other unusual microorganisms, could justify the introduction of antibiotics other than amoxicillin into standard prophylaxis protocols in the future in order to improve the antimicrobial spectrum in certain circumstances.
