Tetracyclines are drugs in the antibiotic class of active ingredients. They belong to the broad-spectrum antibiotics and are used for bacterial infections.
What is tetracycline?
Tetracyclines are drugs in the antibiotic drug class. They belong to the broad-spectrum antibiotics. Tetracyclines are various antibiotics that were first mentioned by Benjamin Minge Duggar in 1948. The drugs were discovered in the research department of the drug manufacturer Pfizer. Tetracyclines were patented in 1955. Tetracyclines were initially isolated from bacterial species. This resulted in chlortetracyclines and oxytetracyclines. The tetracyclines available today are chemically modified derivatives of these original substances. They have higher tolerability and also exhibit more favorable pharmacokinetics. The tetracyclines include doxycyclines, minocyclines, and lymecyclines. These differ in their tolerability and pharmacokinetic properties. A derivative of the tetracyclines is tigecycline. This substance is used primarily for severe infections with multidrug-resistant germs.
Pharmacologic action
Tetracyclines bind to a special subunit of bacterial ribosomes. Ribosomes are small cellular particles composed of proteins. They are responsible for protein biosynthesis in cells. Without this synthesis, division of bacteria is not possible. Due to the tetracyclines, specifically the aminoacyl-tRNA on the 50s underside of the ribosomes cannot align properly. The required peptidyltransferase reaction cannot be carried out. Thus, peptide chain termination occurs during protein synthesis in the bacteria. It is possible that the toxicity of the drug is based on knockdown of 30-S ribosomes, which are present in the mitochondria of host cells.
Medical application and use
The drug is effective against Gram-positive and against Gram-negative bacteria. Bacterial genera that lack a cell wall are also sensitive to the antibiotic. These cell-wall-less bacteria include, for example, mycoplasmas or chlamydiae. Borrelia and spirochetes also react to tetracycline. Borrelia are the pathogens of Lyme disease. The disease is transmitted by ticks and is accompanied by dermatological and neurological symptoms. Affected individuals also suffer from joint pain and constant fatigue. Spirochetes are the causative agents of syphilis. Syphilis is usually transmitted during sexual intercourse. For a long time, the disease had almost disappeared in Germany, but it is currently on the rise again. A typical indication for tetracycline is pneumonia. The drug is used primarily for atypical pneumonia. It is also the agent of choice for Q fever. Q fever is a zoonotic disease caused by the bacterium Coxiella burnetii and is associated with flu-like symptoms. Tetracycline is also used for infections of the genitourinary system. One possible indication here is inflammation of the prostate (prostatitis). Infections of the skin are also typical areas of application for tetracyclines. For example, the drugs are frequently used to treat acne vulgaris. Other indications for the drug are plague, cholera, tularemia and brucellosis. Tularemia is transmitted by free-living rodents. The causative agent is the bacterium Francisella tularensis. Brucellosis is an infectious disease caused by gram-negative rod-shaped bacteria. It can occur in humans and in animals. Most infections are subclinical. However, night sweats, chills and nausea may occur. Many courses of the disease heal spontaneously, but there are also protracted chronic inflammations that are accompanied by serious symptoms such as depression or constant insomnia.
Risks and side effects
Main side effects of tetracycline are nonspecific gastrointestinal symptoms. In particular, vomiting and nausea occur quite frequently. Neurologic dizziness may also be observed. Furthermore, itching and skin rashes may occur. Especially at high doses, tetracyclines cause an increase in transaminases. Inflammation of the pancreas (pancreatitis) may occur. The drug not only damages harmful bacteria. The site flora of the vagina, skin and intestine is also severely affected.Particularly with prolonged use, fungal diseases of the vagina (vaginal fungus) and skin (skin fungus) can therefore occur. These are also known as candidiasis. Another serious secondary disease after taking tetracycline is pseudomembranous colitis. This involves severe inflammation of the colon. The damage to the intestinal flora usually manifests itself in the form of digestive disorders and diarrhea. Pregnant women and nursing mothers must not take tetracycline. The drug is incorporated together with calcium into the bones and tooth enamel of the unborn child. On the one hand, this discolors the teeth, and on the other, the incorporation of the mineral leads to an increased susceptibility to fracture. Tetracyclines may therefore only be used from the age of ten to twelve. Since tetracyclines can form complexes with metal ions such as magnesium, iron or aluminum, they must be taken separately from calcium-containing foods such as milk or quark. Antacids, magnesium preparations or iron preparations must also not be taken together with the antibiotic. Women should note that tetracyclines can reduce the effect of oral contraceptives. Therefore, additional contraception should be used while taking the drug. Tetracyclines should not be taken during isotretinoin therapy. Both drugs can dangerously increase intracranial pressure. Of course, tetracyclines must not be taken in case of tetracycline intolerance. Otherwise, severe allergic symptoms may develop. In the worst case, allergic shock will occur.
