Which penicillin is administered intravenously for serious infections?

The correct answer is Penicillin G, which is specifically formulated for intravenous administration. This form of penicillin is favored for treating serious infections, especially those caused by susceptible gram-positive bacteria, including certain strains of streptococci and staphylococci.

Penicillin G is effective due to its pharmacological properties, which allow it to achieve high serum levels rapidly. The intravenous route ensures immediate availability in the bloodstream, which is critical in severe cases where prompt treatment is necessary.

The other options are less suitable for intravenous use: Bicillin LA is designed for intramuscular injection and provides prolonged action but does not have the immediacy necessary for serious infections. Amoxicillin is typically administered orally, making it convenient for less acute situations. Penicillin VK, another oral form, is also not appropriate for serious infections due to its slower absorption and lower serum concentrations. Therefore, Penicillin G stands out as the appropriate choice for direct intravenous use in critical settings.