Final answer:
Penicillin G is administered either intravenously or intramuscularly due to its instability in acidic environments. It can be combined with aminoglycosides or cephalosporins for a synergistic effect through combined inhibition of bacterial cell wall and protein synthesis.
Step-by-step explanation:
Penicillin G is a narrow-spectrum antibiotic predominantly administered via the parenteral route, specifically intravenously (IV) or intramuscularly (IM), to treat several bacterial diseases. Unlike its oral counterpart penicillin V, penicillin G cannot be taken orally due to its instability in acidic environments, such as the stomach. This drug is particularly useful in combating infections caused by gram-positive bacteria (which include bacteria like staphylococci and streptococci) and is also effective against some gram-negative bacteria including Escherichia coli.
For a synergistic effect, penicillin G can be combined with other classes of antibiotics, such as aminoglycosides. This combination works effectively because while penicillin G inhibits cell wall synthesis, aminoglycosides hinder protein synthesis in bacteria, thereby intensifying the bactericidal action. Cephalosporins are another class that can be synergistic with penicillin G due to their similar mode of action of inhibiting peptidoglycan synthesis in the bacterial cell wall.