Benzylpenicillin is a classic form of penicillin. The antibiotic agent is also known as penicillin G.
What is benzylpenicillin?
Benzylpenicillin, also known as penicillin G, is one of the antibiotics. It comes from the beta-lactam antibiotics and is used to treat various bacterial infectious diseases. The discovery of benzylpenicillin took place in 1928 by the Scottish bacteriologist Alexander Fleming (1881-1955). The physician was awarded the Nobel Prize in 1945 for the discovery of the antibiotic penicillin. Penicillin G is produced by the mold Penicillium notatum. Even in modern times, benzylpenicillin is obtained fermentatively from fungal cultures rather than synthetically. Penicillin G is considered the parent substance of all penicillins. It gave rise to a large number of derivatives whose properties changed. The disadvantages of the substance include its sensitivity to the bacterial enzyme penicillinase and oral inefficacy, which is due to acid instability. For this reason, benzylpenicillin can be administered only by bypassing the intestine.
Pharmacologic Action
Benzylpenicillin possesses bacteriostatic activity. Its spectrum of activity includes Gram-positive bacteria, Gram-negative anaerobic rods, Gram-negative cocci species, and spirochetes. Meningococci, pneumococci, clostridia, borrelia, corynebacteria, non-penicillin-forming staphylococci, alpha- and beta-hemolytic streptococci, leptospires, Bacteroides species, as well as Treponema pallidum and Bacillus anthracis are considered penicillin-G sensitive. However, the number of bacterial strains resistant to penicillin G has continued to increase in recent years. This is especially true for gonococci. Benzylpenicillin has the effect of inhibiting the growth of bacteria. For this purpose, the cell wall of the germs is blocked by the antibiotic substance. However, some bacteria have the ability to destroy penicillin G because they are equipped with the protein beta-lactam. In this way, they achieve a natural resistance to the drug. Since oral administration is ineffective due to the breakdown of the substance by gastric acid, benzylpenicillin must always be administered in the form of an infusion or injection. However, because the duration of action of the antibiotic is very short, it is necessary to administer it several times a day. Benzylpenicillin benzathine is considered a longer-acting benzylpenicillin and can be administered once a week or once a month. After a short infusion, there is a rapid increase in the plasma concentration of penicillin G. However, after only five hours, the equally rapid decrease of the active substance occurs. In the case of intramuscular administration, absorption is complete after approximately 30 minutes. The plasma concentration is lower than in the case of an intravenous infusion. Benzylpenicillin is eliminated from the body primarily by the kidneys. There is hardly any metabolism. The degree to which penicillin G concentrates in individual body tissues varies. Thus, relatively high concentrations occur in the kidneys, liver and lungs, while they are quite low in the bones as well as in the brain.
Medical application and use
Benzylpenicillin is suitable for the treatment of infections whose bacterial originators are sensitive to the antibiotic. These are respiratory infections, infections in the ear, nose, and throat region, vaginal infections, and laryngitis. However, endocarditis (inflammation of the inner lining of the heart), meningitis (inflammation of the meninges), osteomyelitis (inflammation of the bone marrow), sepsis (blood poisoning), peritonitis (inflammation of the peritoneum) or infections of the skin can also be effectively treated with penicillin G. Other indications include rheumatic fever, leptospirosis, scarlet fever, erysipelas, diphtheria, Lyme disease, gas gangrene and syphilis. In the case of wound infection or tetanus, on the other hand, a check is necessary because their pathogens are mostly insensitive to benzylpenicillin. In some diseases, penicillin G is also combined with another antibiotic. The dose of benzylpenicillin depends on the particular disease. The dosage is given in International Units (IU). One million IU carry the designation ME. The maximum dosage is 10 ME, which can be administered up to four times a day.
Risks and side effects
Treatment with penicillin G can sometimes result in unwanted side effects. These include diarrhea, bloating, nausea, vomiting, changes in taste, allergic reactions such as severe skin rash or hives, agranulocytosis, dry mouth, kidney inflammation, anemia, serum sickness, inflamed blood vessels, muscle twitching, and cramps. Some patients also suffer from swelling and pain at the injection site. If the patient must undergo treatment with benzylpenicillin for a prolonged period of time, there is a risk of fungal or bacterial infection of the colon. As a result, there is a risk of intestinal inflammation accompanied by diarrhea. In this case, the treatment must be discontinued immediately after consultation with the attending physician. Instead, other antibiotics are used later. Penicillin G must not be administered at all if the patient is hypersensitive to penicillins. If the patient suffers from special forms of leukemia or Pfeiffer’s glandular fever, the physician must carefully weigh up the risks and benefits for the patient before administering it. The use of penicillin G during pregnancy is considered safe. However, it is important to consult with the physician. Since the antibiotic agent can pass to the baby via the mother’s milk, there is a risk of disturbances in the infant’s intestinal flora. The affected infants suffer from diarrhea and intestinal inflammation. In addition, allergic reactions may develop later. For this reason, consultation with the doctor is recommended before using the antibiotic, even during the breastfeeding period. Because benzylpenicillin affects the intestinal flora and can cause diarrhea, it is possible that the effectiveness of hormonal contraceptives such as the birth control pill may be reduced. For this reason, additional use of diaphragms or condoms is recommended.
