The name given by Sir Alexander Fleming, in 1929, to an antibacterial substance produced by the mould Penicillium notatum. The two great advantages of penicillin are that it is active against a large range of bacteria and that, even in large doses, it is non-toxic. Penicillin diffuses well into body tissues and fluids and is excreted in the urine, but it penetrates poorly into the CEREBROSPINAL FLUID.
Penicillin is a beta-lactam antibiotic, one of a group of drugs that also includes CEPHALOSPORINS. It acts by interfering with the cell-wall growth of multiplying bacteria.
Among the organisms to which it has been, and often still is, active are: streptococcus, pneumococcus, meningococcus, gonococcus, and the organisms responsible for syphilis and for gas gangrene (for more information on these organisms and the diseases they cause, refer to the separate dictionary entries). Most bacteria of the genus staphylococcus are now resistant because they produce an enzyme called PENICILLINASE that destroys the antibiotic. A particular problem has been the evolution of strains resistant to methicillin – a derivative originally designed to conquer the resistance problem. These bacteria, known as METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA), are an increasing problem, especially after major surgery. Some are also resistant to other antibiotics such as vancomycin.
An important side-effect of penicillins is hypersensitivity, causing rashes and sometimes ANAPHYLAXIS, which can be fatal.
These include the following broad groups: benzylpenicillin and phenoxymethyl-penicillin; penicillinase-resistant penicillins; broad-spectrum penicillins; antipseudomonal penicillins; and mecillinams.
is given intramuscularly, and is the form that is used when a rapid action is required.
(also called penicillin V) is given by mouth and used in treating such disorders as TONSILLITIS.
A broad-spectrum antibiotic (that is, it deals with many different types of bacteria) derived by semi-synthesis from the penicillin nucleus. Its value is that it is active against gram-negative (see GRAM'S STAIN) micro-organisms such as E. coli and the salmonellae.
A semi-synthetic penicillin that must be given by injection; its main use is in dealing with infections due to Pseudomonas pyocanea. It is the only penicillin active against this micro-organism which can be better dealt with by certain non-penicillin antibiotics.
are carboxypenicillins used to treat infections caused by Pseudomonas aeruginosa and Proteus.
also a semi-synthetic penicillin, is active against many penicillin-resistant staphylococci and has the practical advantage of being active when taken by mouth.
is another penicillinase-resistant penicillin, effective against most gram-negative bacteria.
is of value in the treatment of infections with salmonellae (see FOOD POISONING), including typhoid fever, and with E. coli (see ESCHERICHIA). It is given by injection. There is a derivative, pivmecillinam, which can be taken by mouth.
is a carboxypenicillin used mainly for serious infections caused by Pseudomonas aeruginosa, though it is also active against some gram-negative bacilli. Ticarcillin is available only in combination with clavulanic acid.