Tuberculation cavity

Pyrazinamide is well absorbed from the GI tract and is widely distributed throughout the body. It penetrates tissues, macrophages, and tuberculous cavities and has excellent activity on the intracellular organisms its plasma half-life is 9 to 10 hours in patients with normal renal function. The drug and its metabolites are excreted primarily by renal glomerular filtration. 

PAS is readily absorbed from the GI tract and is widely distributed throughout body fluids except cerebrospinal fluid. It penetrates tissues and reaches high concentrations in the tuberculous cavities and caseous tissue. Peak plasma levels are reached within 1 to 2 hours of drug administration, and the drug has a half-life of about an hour. PAS is primarily metabolized by hepatic acetylation. When combined with isoniazid, PAS can function as an alternative substrate and block hepatic acetylation of isoniazid, thereby increasing free isoniazid levels. Both the acetylated and unaltered drug are rapidly excreted in the urine. The concentration of PAS in urine is high and may result in crystalluria. 

Isoniazid monotherapy leads to resistance. This resistance typically develops after a few weeks of therapy but can vary. Approximately 1 in 1(P tubercle bacilli will be genetically resistant to isoniazid since tuberculous cavities may contain as many as ICP microorganisms, it is not surprising that isoniazid selects for resistant bacteria. The incidence of primary resistance to isoniazid in the... 

Internal surfaces were moderately tuberculated (Fig. 3.14). Extremely thick, hard magnetite shells capped large internal cavities (Fig. 3.9). Pipe cross-sectional area was reduced by at least 30% in some places. Tubercles were aligned with flow, indicating that growth occurred during service. No failure occurred, and deepest metal loss was only 0.093 in. (0.033 cm) from the nominal pipe wall thickness of 0.225 in. (0.572 cm). 

Cliaracters.—Hard, heavy, globular bodies, varying in size from half an inch to three fourths of an inch in diameter tuberculated on the surface, the tubercles and intervening spaces smooth bluish-green colour superfl-cially, yellowish-white within, with a small central cavity intensely astringent. 

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