Antituberculous drugs are specific chemotherapeutic agents that inhibit the growth and viability of Mycobacterium tuberculosis. These medications are used in prolonged combination therapy regimens to treat severe chronic infections.
First drugStreptomycin (discovered by Selman Waksman in 1943)
ClassificationAntibiotics and synthetic agents
Pathogen Characteristics and Resistance Factors
Treating tuberculosis is challenging due to the unique biological features of the pathogen. Mycobacteria exhibit primary resistance to many conventional antibiotics.
Key factors reducing the efficacy of drug therapy:
Slow growth rate: standard antimicrobial drugs target rapidly dividing cells.
Depressed metabolism: suppression of cellular metabolic processes decreases drug activity.
Cell wall properties: the pathogen's envelope is rich in lipids, creating a reliable barrier against drug penetration.
Intracellular localization: the mycobacterium acts as an intracellular parasite, requiring agents capable of penetrating host cells.
Principles of Tuberculosis Therapy
The treatment strategy is based on the pathogen's properties and aims to achieve a sustained clinical outcome:
Prolonged course: therapy continues from six months to a year or longer to prevent potential relapses.
Combination therapy: mandatory use of multiple drugs simultaneously helps successfully overcome mycobacterial drug resistance.
Classification of Antituberculous Drugs
Depending on their origin, this pharmacological arsenal is divided into two major groups:
The disease presents as a severe chronic infection with various pathological focus localizations:
Respiratory tuberculosis: pulmonary form.
Extrapulmonary tuberculosis: involvement of the osteoarticular and urogenital systems, skin, central nervous system, and abdominal cavity organs.
Mnemonic
To remember the classification, group them as follows: antibiotics include aminoglycosides (streptomycin, kanamycin, amikacin) and others (rifampicin, cycloserine), while synthetic agents include INH derivatives (isoniazid), PAS, and thioamides.
Frequently asked questions
Which antituberculous drugs are classified as first-line (primary) agents?
They are used for newly diagnosed tuberculosis cases when the pathogen is susceptible to these medications.
What is the mechanism of action of isoniazid on Mycobacterium tuberculosis?
The mechanism of action of isoniazid involves the inhibition of mycolic acid synthesis. These acids are a specific component of the cell wall of Mycobacterium tuberculosis. Human host cells lack mycolic acids, ensuring high selectivity of the drug: it is highly toxic to mycobacteria while exhibiting low toxicity to humans.
What specific adverse effects are caused by rifampicin?
Rifampicin causes several specific and systemic adverse effects:
Discoloration of body fluids — urine, saliva, and tears turn orange-red.
Hepatotoxicity — impaired liver function, risk of hepatitis.
Hematological abnormalities — thrombocytopenia and anemia.
Nephrotoxicity — risk of renal failure.
"Flu-like syndrome" — fever, arthralgia, and myalgia.
Which antituberculous agents are classified as reserve (second-line) drugs?
Reserve antituberculous agents (second-line drugs) are prescribed when mycobacteria develop resistance to primary medications:
Prothionamide and ethionamide — isonicotinic acid thioamide derivatives.
Kanamycin and amikacin — aminoglycoside antibiotics.
Lomefloxacin and other fluoroquinolones — synthetic antibacterial agents.
Capreomycin (Capreomycin) and florimycin — polypeptide antibiotics.
Cycloserine, rifabutin, and aminosalicylic acid — other reserve agents.
What is the mechanism of action of aminoglycosides in tuberculosis treatment?
The mechanism of action of aminoglycosides in tuberculosis treatment involves the inhibition of protein synthesis. Aminoglycosides exert a bactericidal effect.
Why are conventional antibiotics largely ineffective against Koch's bacillus?
This is due to the slow growth rate and depressed metabolism of mycobacteria, the high lipid content in their cell wall, and the intracellular localization of the pathogen.
What are the main principles of tuberculosis treatment?
Therapy must be prolonged (from 6 months to a year or more) and strictly combination-based to prevent the development of drug resistance.
Which drug groups comprise the modern arsenal of antituberculous agents?
The arsenal is divided into antibiotics (including aminoglycosides and rifampicin) and synthetic agents (INH derivatives, PAS, and isonicotinic acid thioamide derivatives).
Go deeper
History of the discovery of the first antituberculous drug by Selman Waksman
Detailed pharmacological profile of aminoglycosides
Isonicotinic acid hydrazide derivatives and their features
Properties of p-aminosalicylic acid (PAS) derivatives
Extrapulmonary forms of tuberculosis and their specific pathology