Final answer:
Potassium or Sodium salts of Penicillin G, when administered in large, rapid IV doses, can be lethal due to high ionic content and risk of cardiotoxicity. Penicillin G benzathine results in fatal reactions if given intravenously, as it is intended for intramuscular use only.
Step-by-step explanation:
The Penicillin G preparation that can potentially be lethal if injected intravenously (IV) is the Potassium or Sodium salt forms of the drug in large, rapid doses, due to their high ionic content. These forms should be administered cautiously to avoid potential high serum levels that can lead to cardiotoxicity or other severe reactions, including death. Penicillin G benzathine cannot be used IV at all, as it is only meant for intramuscular (IM) administration and can cause severe and potentially fatal reactions if given intravenously.
Although Penicillin G is the drug of choice for treating many bacterial infections such as syphilis, pneumonia, and diphtheria, the route of administration is critical for patient safety. Due to the risk of anaphylactic shock, it is also vital to screen patients for penicillin allergy before administering this medication.