FIRST LINE DRUGS
They include drugs like-
•INH– INH means isonicotinic acid hydrazide commonly known as isoniazid, they inhibit the synthesis of mycolic acid which is important component of the mycobacterium.It is the back bone for treatment of TB.INH can kill intracellular as well as extracellular bacteria,it is a bactericidal drug.But INH is not effective against Mycobacterium avium intercellularae (MAI)
•RIFAMPICIN– It bind to the beta subunit of the DNA dependent RNA polymerase and inhibit RNA synthesis in bacteria.
Rifampicin can’t bind human RNA polymerase and it therefore selectively destroy the bacteria.It is also a bactericidal drug and along with INH forms the back bone for treatment of TB.
Rifampicin is effective against wide class of Bacterias like-
-Mycobacterium tuberculosis
-Mycobacterium avium intercellularae
-Mycobacterium leprae
-Brucella abortus
-Staphyllococcus
-Hemophillus influnzae
•PYRAZINAMIDE– Pyrazinamide is converted to its active metabolite pyrazinoic acid by an enzyme pyrazinamydase present in the mycobacteria this metabolite may inhibit the synthesis of mycolic acids.It also have bactericidal action.
Sometime patient may complain of arthralgia as an adverse effect of pyrazinamide so in this case we will stop the drug for sometime.
•ETHAMBUTOL– It have bacteriostatic action and acts by stopping mycolic acid synthesis by bacteria.It is effective against both Mycobacterium avium intercellularae and Mycobacterium TB.
•STREPTOMYCIN– It is member of Aminoglycoside group, it has bactericidal action.It acts by sticking to the ribosomes of bacteria which leads to stoppage of protein synthesis of bacteria and then the bacteria is killed.
SECOND LINE DRUGS
They include drugs like
•THIACETAZONE– It inhibits with mycolic acid synthesis and have bacteriostatic type of action.
•PAS– para-amino salicylic acid inhibits with folic acid synthesis of bacteria and is bacteriostatic drug.
•MOXIFLOXACIN– They inhibit DNA gyrase enzyme of bacteria and is bactericidal in action.
•FLUOROQUINOLONES– they enter into the cell and destroy intracellular mycobacteria
•CYCLOSERINE– inhibit cell wall synthesis, also effective against some gram positive organisms.
•RIFABUTIN/RIFAPENTINE– acts via the inhibition of DNA dependent RNA polymerase in gram +ve and some gram negative bacteria.
•LINEZOLID– It is used when even second line drugs fails to control TB infection I e it is used in extreme drug resistant TB (XDR-TB).
Linezolid is also effective against-
Staphylococcus aureus
Methicillin resistant streptococcus aureus (MRSA)
Vancomycin resistant streptococcus aureus (VRSA)
Drug resistant streptococcus pneumoniae (DRSP)
Serious toxicity of some drugs:-
•INH– Peripheral neuritis, hepatitis, seizures and psychosis.
To prevent neurotoxicity and neuropathy pyridoxine tablet is also given along with INH.
Also we should keep in mind that before starting anti TB drug, LFT should be done so as to check the condition of liver and also if in between treatment of TB the patient complains of symptoms related to liver then we will stop the INH as it is hepatotoxic.
•RIFAMPICIN– Hepatotoxicity, Flue like syndrome, Nephritis- urine and secretion are orange red colored.
•PYRAZINAMIDE– Hepatotoxicity, arthralgia, rhabdomyolysis, hyperurecemia.
•STREPTOMYCIN– Ototoxicity, nephrotoxicity, patient may complain of tinnitus or hearing impairment like problems.
•ETHAMBUTOL– Optic neuritis with inhibition of visual acuity and red-green colour blindness.
•THIACETAZONE– Anemia, skin rashes, etc
•LINEZOLID– If it is given for too long then it causes loose motions and in some patients this loose motions may become bloody.
Contributor- Medico Vikram saxena
