Penicillin G and Penicillin V are examples of β-lactam antibiotics with Penicillin G having a narrow spectrum against gram-positive bacteria and Penicillin V designed for oral administration. Semisynthetic penicillins like ampicillin and amoxicillin have broader spectrums due to added amino groups.
Penicillins are a subclass of β-lactam antibiotics which are characterized by the presence of a β-lactam ring that is key to their antibacterial activity. Two notable examples of penicillins are Penicillin G and Penicillin V. Penicillin G is a natural antibiotic that has a narrow spectrum of activity, primarily against gram-positive bacteria, and is administered intravenously or intramuscularly.
Penicillin V, also a natural penicillin, is similar to Penicillin G but can be taken orally. Semisynthetic modifications to these penicillins, such as adding an amino group to create aminopenicillins like ampicillin and amoxicillin, have broadened their spectrum to include more gram-negative bacteria. Methicillin was developed as a penicillinase-resistant penicillin to combat bacterial resistance.
So, Penicillin G and Penicillin V represent the two classic forms of penicillin, with different spectrums of activity and methods of administration being their distinguishing factors.