Penicillin V is a penicillin beta-lactam antibiotic used in the treatment of bacterial infections caused by susceptible, usually gram-positive, organisms. The name "penicillin" can either refer to several variants of penicillin available, or to the group of antibiotics derived from the penicillins. Penicillin V has in vitro activity against gram-positive and gram-negative aerobic and anaerobic bacteria. The bactericidal activity of Penicillin V results from the inhibition of cell wall synthesis and is mediated through Penicillin V binding to penicillin binding proteins (PBPs). Penicillin V is stable against hydrolysis by a variety of beta-lactamases, including penicillinases, and cephalosporinases and extended spectrum beta-lactamases. By binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall, Penicillin V inhibits the third and last stage of bacterial cell wall synthesis. Cell lysis is then mediated by bacterial cell wall autolytic enzymes such as autolysins; it is possible that Penicillin V interferes with an autolysin inhibitor. Used for the treatment of mild to moderately severe infections (e.g. dental infection, infections in the heart, middle ear infections, rheumatic fever, scarlet fever, skin infections, upper and lower respiratory tract infections) due to microorganisms.

Penicillin G, also known as benzylpenicillin, is a penicillin derivative commonly used in the form of its sodium or potassium salts in the treatment of a variety of infections. It is effective against most gram-positive bacteria and against gram-negative cocci. It is administered intravenously or intramuscularly due to poor oral absorption. Penicillin G may also be used in some cases as prophylaxis against susceptible organisms. Microbiology Penicillin G is bactericidal against penicillin-susceptible microorganisms during the stage of active multiplication. It acts by inhibiting biosynthesis of cell-wall mucopeptide. It is not active against the penicillinase-producing bacteria, which include many strains of staphylococci. Penicillin G is highly active in vitro against staphylococci (except penicillinase-producing strains), streptococci (groups A, B, C, G, H, L and M), pneumococci and Neisseria meningitidis. Other organisms susceptible in vitro to penicillin G are Neisseria gonorrhoeae, Corynebacterium diphtheriae, Bacillus anthracis, clostridia, Actinomyces species, Spirillum minus, Streptobacillus monillformis, Listeria monocytogenes, and leptospira; Treponema pallidum is extremely susceptible. Adverse effects can include hypersensitivity reactions including urticaria, fever, joint pains, rashes, angioedema, anaphylaxis, serum sickness-like reaction.

Benethamine penicillin is a medium-long-acting insoluble penicillin salt. After a single injection, this salt acts and bacteriostatic level of penicillin is maintained in the blood for three to six days.