Which of the anti tuberucular drug crosses the blood brain barrier.
a. INH
b.Rifmapaicn.
c. Ethambutol.
d. Streptomycin

Ans: A, B 

The literature relating to cerebrospinal fluid penetration of antituberculosis agents is reviewed. 

Amongst the essential antituberculosis agents isoniazid has the best CSF pharmacokinetics reaching peak concentrations (C(max)) only slightly less than in blood. 

Pyrazinamide also has good CSF penetration and in children receiving dosages of 40 mg/kg the CSF C(max) exceeds the proposed minimal inhibitory concentration of 20 μg/ml. 

Streptomycin other aminoglycosides and ethambutol have poor CSF penetration and cannot be agents of first choice for TBM treatment. 

Rifampicin at dosages used in adults seldom reaches CSF concentrations exceeding MIC, but does so more frequently in children when dosages of up to 20 mg/kg are used. 

The non-essential agents ethionamide, the fluoroquinolones, with the exception of ciprofloxacin, and cycloserine (terizadone) have relatively good CSF penetration and are recommended for TBM treatment.