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Doxycycline is one of the time-tested antibiotics. It was synthesized in the early 60s of the last century by scientists of the American pharmaceutical giant Pfizer. The drug was clinically studied and released under the trade name Vibramycin. A little later, the World Health Organization included Doxycycline in the list of the most important medicines needed for human health. It would seem that the development of the pharmaceutical industry and the production of new broad-spectrum antibiotics does not leave the chance of survival to such “old people” as Doxycycline. However, it is not. And the fact that the drug was found in. Its niche is an indisputable fact. What is the antibiotic has for long? What side effects should be feared? In this article we will try to understand the properties of Doxycycline.
Mechanism of action
Tetracyclines inhibit protein synthesis by binding to the ZOB subunit of bacterial ribosomes and blocking the attachment of aminoacyl-tRNA to the aminoacyl site of the ribosome-mRNA complex. Through the outer membrane of Gram-negative bacteria, these preparations penetrate through simple diffusion through the pores formed by porin-mi proteins, and through the cytoplasmic membrane through a special system of active transport. The mechanism of penetration of tetracyclines into the cells of gram-positive bacteria is not well understood, but it also requires energy expenditure.
In high concentrations, tetracyclines disrupt protein synthesis in mammalian cells. However, due to the less affinity for the ribosomes of these cells and the absence of a special active transport systemavailable in bacteria, in therapeutic concentrations, tetracyclines only act on bacterial cells.
Composition and form of release
So, Doxycycline is a semisynthetic antibacterial drug from the group of tetracyclines. It derivatives: monohydrate, hydrochloride and calcium salt are active in relation to microorganisms and chemical stability. It is these three compounds that are used as active substances.
Oral Doxycycline is available in capsules and tablets of 100 and 200 mg. Parenterally, that is, intramuscularly or intravenously, this antibiotic is not used.
Pharmacological action and spectrum of activity of Doxycycline
Doxycycline has a pronounced bacteriostatic effect, blocking the synthesis of proteins in the cell of a pathogenic microorganism. An important advantage of the drug is its ability to penetrate the bacterial cell wall. Due to this, It exerts an antibacterial effect on intracellular microorganisms.
The spectrum of pharmacological activity is very impressive and includes a variety of pathogens.
Doxycycline is active against gram-negative bacteria, which are usually associated with intestinal infections. This group includes campylobacteria, enterobacteria, intestinal and hemophilic rods, klebsiella, causative agents of gonorrhea, shigella, cholera vibrio and other microorganisms.
A distinctive feature of tetracycline antibiotics, including It, is low activity against most gram-positive bacteria. This explains the lack of effectiveness of tetracycline antibiotics for respiratory infections.
Almost the only gram-positive microorganism that has sensitivity to It is Streptococcus pneumoniae, the most common pathogen of pneumonia.
Doxycycline exerts a bactericidal action against anaerobic pathogens, including Propionibacterium acnes. It is these bacteria that are associated with acne.
The antibiotic is effective in infections caused by chlamydia Chlamydophila psittaci and Chlamydia trachomatis, Mycoplasma pneumoniae Mycoplasma, treponema and ureaplasma.
Note that there is evidence of Doxycycline activity against asexual erythrocyte forms of malarial plasmodium. However, the exact mechanism of action is not yet established.
The drug is absolutely ineffective in infections caused by the proteus, Pseudomonas aeruginosa and fungi.
Doxycycline in a number of other tetracyclines
In comparison with other tetracyclines, Doxycycline has several advantages: – The antibiotic practically does not inhibit the normal intestinal microflora. Due to this property, the intake of medication is very rarely accompanied by diarrhea; – most fully absorbed. The remaining tetracycline antibiotics have an order of magnitude less bioavailability; – long acting.
The half-life of the drug is long enough (up to 10 hours), so it can be taken only twice a day. I would like to note that cross-resistance exists between all the agents of the tetracycline group. That is, if Tetracycline or Metacyclin did not have any effect, then, from the Doxycycline effect, waiting, alas, is not worth it. The same resistance exists between Doxycycline and antibiotics of the penicillin series.
Doxycycline – indications for use
Indications for use Doxycycline are based on the activity spectrum. Doctors usually do not prescribe tetracyclines for catarrhal infections – these diseases are caused most often by staphylococci and streptococci. But the drug is widely used for rare infections, as well as for sexually transmitted diseases.
The main diseases in which Doxycycline is prescribed include respiratory tract infections (pneumonia and bronchitis in adults and children) caused by Mycoplasma pneumoniae, Chlamydia trachomatis and Streptococcus pneumoniae.
In most cases of pneumonia and bronchitis before the appointment of Doxycycline, identification of the pathogen is carried out. This is necessary in order to exclude infection with staphylococcus and streptococcus, which are also often the cause of pneumonia.
It is widely used for sexually transmitted diseases: chlamydia, gonorrhea, mycoplasmosis, ureaplasmosis and even syphilis. Doxycycline successfully copes with uncomplicated urethritis (inflammation of the urethra), cervicitis (inflammation of the cervical canal) and proctitis (inflammation of the rectum) associated with chlamydia and mycoplasmal infection.
Despite the fact that chlamydia are sensitive to It, it is not always possible to achieve their elimination in monotherapy. In practice, the treatment regimens for chlamydia include several drugs (tetracyclines and macrolides), or shock doses of macrolides, in particular Sumamed.
Doxycycline is one of the most effective antibacterial agents for ureaplasmosis. Antibiotic is used as a first line drug for non-gonococcal urethritis caused by Ureaplasma urealyticum (ureaplasma).
Doxycycline is also prescribed for infection with gram-negative bacteria, including mild chancroid, plague, tularemia, campylobacter fetal infections that cause Campylobacter fetus. The treatment of brucellosis includes the combined use of Doxycycline and Streptomycin.
It remains to add that It is also used to prevent malaria associated with Plasmodium falciparum. The medicine is prescribed for travelers who are in endemic areas for a short time (up to 4 months).
Acne and Rosacea: Doxycycline for acne
Separate words deserve the activity of an antibiotic against microorganisms that cause skin diseases. Due to these qualities it is used for oral treatment of acne (acne) and rosacea. Simply put, Doxycycline is one of the effective medicines that help get rid of acne.
But do not forget that doctors should treat dermatologists. Therapy of acne and rosacea is a complex and lengthy process. The treatment regimen includes not only one remedy, but the course of therapy can last several months. Therefore, you need to be patient, and most importantly – to find your dermatologist and not engage in self-medication.
Standard dosage of Doxycycline according to the instructions
Immediately note that the usual dose and frequency of Doxycycline is different from other antibiotics from the tetracycline group. For adults, the usual dose of oral Doxycycline is 200 mg on the first day of treatment, divided into two doses (every 12 hours).
After that, the dosage is reduced to 100 mg per day once. To treat more severe infections, it is recommended to take 100 mg of Doxycycline twice a day for the entire course of therapy. The duration of treatment is determined individually.
Note that in the treatment of streptococcal infection treatment course should be at least 10 days. Separately, I would like to say about the therapy of the pulmonary form of anthrax. For this purpose, it is recommended to take Doxycycline 100 mg twice a day for at least 60 days.
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