Complex sentence: Benzathine benzylpenicillin (rINN), also known as benzathine penicillin, is slowly absorbed into the circulation, after intramuscular injection, and hydrolysed to benzylpenicillin "in vivo".
Split into simpler sentences: Benzathine benzylpenicillin (rINN) is a form of penicillin also known as benzathine penicillin. It is slowly absorbed into the circulation, after intramuscular injection, and hydrolysed to benzylpenicillin "in vivo".