Tetracyclines are broad spectrum antibiotics with a tetracyclic structure (composed of four rings with 6 terms each), hence the name of the whole class. When we talk about tetracycline we mean chlorotetracycline, which was the first tetracycline discovered by Benjamin Duggar in 1945. Duggar discovered chlorotetracycline at Lederle Laboratories while working under the supervision of the Indian scientist Yellapragada Subbarao.
In 1950 Professor Robert Woodward of Harvard University, collaborating with a team of researchers from the pharmaceutical company Pfizer (KJ Brunings, Peter P. Regna, Francis A. Hochstein, Abraham Bavley, CR Stephens, LH Conover and Richard Pasternack), isolated the molecule from the strain Streptomyces rimosus and he determined the chemical structure of oxyteracycline (trade name Terramicina ®), for which he also obtained the patent on the production process. The research process that led to this discovery lasted more than two years.
Tetracyclines are antibiotics with a broad spectrum of action indicated for the treatment of many bacterial infections. Today tetracyclines are used in the treatment of acne, in triple therapy for the eradication of Helicobacter pylori, and in the treatment of rosacea; historically speaking, it can be said that tetracyclines have been a very useful tool for reducing cholera deaths. Tetracyclines have been widely used both for the therapy of infectious diseases and illegally as an additive to animal feed, with the aim of promoting their growth (the addition of antibiotics in the feed in order to exterminate the endogenous bacterial flora of animals and increase them weight, can have serious consequences for consumers and is a strictly prohibited practice.) This widespread use has led to the emergence of bacterial strains resistant to tetracyclines, thus leading to a drastic reduction in their use in therapy.
Tetracyclines are considered the antibiotic of choice in rickettsial, mycoplasma and chlamydial infections. Tetracyclines are particularly effective in rickettsiae infections including Rocky Mountain fever, relapsing epidemic typhus (Brill's disease) and vesicular rickettiosis. . Tetracyclines are also widely used for the treatment of sexually transmitted diseases (STDs), as several forms of Chlamydia are known to be sensitive to this class of drugs. Tetracyclines have also been shown to be effective in the treatment of acute and chronic Brucella melitensis infections. , B. suis and B. abortus. The combination of a tetracycline, for example doxycycline, with another antibiotic, for example an aminoglycoside antibiotic such as streptomycin, has given very convincing results in cases of acute brucellosis.
Tetracyclines inhibit the protein synthesis of bacteria by binding to their 30 S ribosomal subunit, thus preventing the access of tRNA and mRNA to the ribosome; consequently, the correct reading of the DNA chain that encodes the proteins is not obtained, and all this leads to an arrest of the protein synthesis of the bacterium, followed by its death.
The discovery of tetracyclines was a very important event because, in addition to allowing the treatment of many pathologies, it opened new horizons to the discovery and synthesis of other antibiotics.
Dosage and method of use
The recommended dose of tetracycline for the treatment of acne in adults is 1000 mg / day, divided into two daily doses over a period of two weeks, which can vary depending on the severity and nature of the infection.
In the triple therapy for the "eradication of"Helicobacter pylori, the recommended dose of tetracycline is 2000 mg / day, divided into 4 daily administrations, one every six hours. The expected duration of treatment is 14 days.
The recommended dose of tetracycline in the treatment of bronchitis is 2000 mg / day, divided into 4 daily administrations, one every six hours. The duration of treatment varies from 7 to 10 days and depends on the severity of the infection. In some cases, especially in patients predisposed to bronchitis, tetracycline is administered for 4 or 5 days in the winter months, to prevent the onset of chronic bronchitis. .
In the treatment of brucellosis it is recommended to use the following therapeutic scheme: 2000 mg / day of tetracycline, to be divided into 4 daily administrations, one every six hours, for a period of three weeks, and 2000 mg / day of intramuscular streptomycin, divided into two daily administrations for the entire first week of treatment, and then 1000 mg / day, in a single daily administration, intramuscularly, during the second week of treatment.
For the treatment of uncomplicated urethral infections, endocervical and rectal infections, the use of 2000 mg / day of tetracycline, divided into 4 daily administrations, one every six hours, is recommended. The expected duration of treatment is at least one week. In case of chlamydial infections it is advisable to check and possibly treat the patient's sexual partner as well.
The recommended dose of tetracycline in the treatment of arthritis and carditis caused by Lyme disease is 2000 mg / day, to be divided into 4 daily administrations, one every six hours. The expected duration of treatment can vary from 2 weeks to 1 month, depending on the severity and nature of the infection. For the treatment of chronic erythema migrans, however, also caused by Lyme disease, it is recommended to use the same dose described above for a slightly different period, ranging from 10 to 30 days.
In the treatment of pneumonia the recommended dose of tetracycline is 2000 mg / day, to be divided into 4 daily administrations, one every 6 hours. The expected duration of treatment varies from 10 to 21 days, depending on the severity of the infection.
For the treatment of rickettsiae infections the recommended dose of tetracycline is as indicated above, and the recommended duration of treatment is one week.
The recommended dose of tetracycline in the treatment of recent syphilis is 2000 mg / day, to be divided into 4 daily administrations, one every six hours for a period of two weeks; the same dose of tetracycline is recommended for the treatment of tertiary syphilis and late syphilis, except that the expected treatment time rises to 4 weeks; or, alternatively, a therapeutic plan can be developed that provides for the intake of 30-40 grams of tetracycline for a period that can vary from 10 to 15 days, obviously by calculating in advance the doses and number of daily administrations. tetracyclines is only recommended if the patient cannot use penicillins.
For the treatment of cystitis, however, the recommended dose of tetracycline remains the same as described above, ie 2000 mg / day, to be divided into 4 daily administrations, one every six hours; the expected duration of treatment varies from 3 to 7 days, depending on the severity of the infection. However, treatment of cystitis with tetracycline should only be undertaken if there are no other therapeutic alternatives.
Contraindications and warnings for use
All tetracyclines have the tetracyclic structure in common and all are amphoteric in character. Tetracyclines are compounds predisposed to give crystalline salts with both acids and strong bases (this is precisely due to their amphoteric character); tetracyclines have a complicated chromophore system that gives rise to absorption spectra characteristic of this class of antibiotics, which extend to the visible giving it the characteristic yellow color. All tetracyclines are capable of chelating metal ions giving rise to chelates, which are insoluble in water and appear to play an appreciable role in the mechanism of action of these antibiotics. Given their amphoteric character, tetracyclines are poorly soluble in water, while their hydrochlorides have a remarkable solubility in water.
Another important characteristic of tetracyclines is that they darken in the light and degrade in the presence of humidity and in an acidic environment to form anhydro-derivatives, which are devoid of antibiotic power and more toxic than the starting antibiotics, this is probably due to the ability to interact in a way non-specific with cell membranes.
Tetracyclines: contraindications and side effects "
