Which of the following statement about Penicillin G is true?

Prophylactic uses (a) Rheumatic fever: Low concentrations of penicillin prevent colonization by streptococci responsible for rheumatic fever. Benzathine penicillin 1 .2 MU every 4 weeks till 18 years of age or 5 years after an attack, whichever is more. (b) Bacterial endocarditis: Dental extractions, endoscopies, catheterization, etc. cause bacteremia which in patients with valvular defects can cause endocarditis. PnG can afford protection, but amoxicillin is preferred now. (c) Agranulocytosis patients: Penicillin may be used alone or in combination with an aminoglycoside antibiotic to prevent respiratory and other acute infections. Pharmacokinetics: Penicillin G is acid labile-destroyed by gastric acid. As such, less than 1 /3rd of an oral dose is absorbed in the active form. Absorption of sod. PnG from i.m. site is rapid and complete; peak plasma level is attained in 30 min. It is distributed mainly extracellularly; reaches most body fluids, but penetration in serous cavities and CSF is poor. However, in the presence of inflammation (sinovitis, meningitis, etc.) adequate amounts may reach these sites. About 60% is plasma protein bound. It is little metabolized because of rapid excretion. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:697,699