Chemotherapy of Tuberculosis 367form) by mycobacterial pyrazinamidase.
Pyrazinamide is a first line drug. Resistance
develops fast, if given alone, hence it is used
in conjunction with isoniazid and rifampi-
cin for shortcourse therapy.
It is absorbed after oral administration
and has good penetration in CSF and is
metabolised in liver and excreted in urine.
Adverse effects include nausea, vomit-
ing, myalgia, arthralgia, hyperuricaemia and
hepatotoxicity. Hypersensitivity reactions
have also been reported.
ETHAMBUTOL
It is tuberculostatic drug effective
against many atypical mycobacteria also.
It acts mainly against rapidly multiplying
organisms in the cavities walls.
Ethambutol is well absorbed from the
GIT after oral administration, distributed
widely and excreted in urine by glomerular
filtration and tubular secretion.
Adverse effects include optic neuritis,
visual disturbance, colour blindness,
hyperuricaemia, skin rash, drug fever,
malaise, confusion, disorientation, head-
ache, nausea, anorexia, vomiting and ab-
dominal pain.
SECOND LINE OR RESERVED DRUGSETHIONAMIDE
It is chemically related to isoniazid and
inhibit the synthesis of mycolic acids. It
is effective against tubercle bacilli resistant
to other drugs and atypical mycobacteria.
After oral administration it is well
absorbed from gastrointestinal tract and
widely distributed throughout body tissues
and CSF. It crosses the placental barrier and
is completely metabolised and less than one
percent of the drug is excreted in urine.
The common side effects are nausea,
vomiting and anorexia. Other effects
include hepatotoxicity, drowsiness,
depression, peripheral neuritis, skin rash,
acne, alopecia and hypertension.PARA-AMINOSALICYLIC ACID (PAS)
It is a tuberculostatic and very less
active drug in the treatment of tuberculosis.
It is used as sodium salt and its larger dose
can cause sodium overload in the body.
Bacteriostatic against Mycobacterium
tuberculosis. It inhibits the onset of
bacterial resistance to streptomycin and
INH.
Readily absorbed from GI tract.
Concentrated in pleural and caseous tissue.
Does not enter CSF. 50% metabolised by
acetylation.
Adverse effects include nausea,
vomiting, diarrhoea, abdominal pain, skin
rashes, goitre, fever and blood dyscrasias.CYCLOSERINE
It is an antibiotic obtained from S.
orchidaceus. It is a chemical analogue of D-
alanine. It is a second line tuberculostatic
antitubercular drug and inhibitor of cell
wall synthesis.
After oral administration, it is rapidly
absorbed and is distributed in various body
tissues including CSF. It is excreted largely
unchanged in urine by glomerular filtration.
It is used for treatment of multidrug resistant
tuberculosis with other primary drugs. It is
also used in acute urinary tract infections
caused by susceptible microorganisms.