Which of the following is true about penicillin
A. Can be given orallyB. Main mechanism of action is cell wall synthesis
inhibition
C. Probenecid given with penicillin G increases its
duration of action
D. Effective against gram-positive bacteria
Ans. A. (Can be given orally)
Explanation
• Antibacterial spectrum: Penicillin G is a narrow spectrum antibiotic; activity is limited primarily to Gram-positive bacteria and few others.
• Penicillin G is acid labile destroyed by gastric acid. So it is not given orally
• The pharmacokinetics of penicillin G is dominated by very rapid renal excretion; about 10% by glomerular filtration and the rest by tubular secretion.
• Tubular secretion of penicillin G can be blocked by probenecid; higher and longer lasting plasma concentrations are achieved.
• Penicillin act by inhibiting cell wall synthesis.
• They are bactericidal drugs.
• Spectrum of activity of PnG is narrow
• It is primarily active against Gram-positive bacteria
• It is usually inactive against Gram-negative bacteria
• Gram-negative cocci (Gonococci and Meningococci) are sensitive to it
• Bacteroides fragilis, mycobacterium TB are resistant rickettsia, chlamydia, protozoa, fungi, viruses are totally insensitive.
