Review of Pharmacology - 9E (2015)

Review of Pharmacology
• No beta lactam antibiotic is effective against MRSA.
• In high concentration, imipenem-cilastatin combination can result in seizures.
Chemotherapy A: General Considerations and Non-specific...
50. Ans. (c) They have acquired penicillin binding protein which has low affinity for β -lactam antibiotic
(Ref: KDT 6/e p700)
• Resistance to most penicillins is due to elaboration of beta-lactamase.
• Methicillin is most resistant penicillin to β-lactamase.
• Staphylococcus aureus develops resistance to methicillins by acquisition of altered penicillin binding proteins.
51. Ans. (a) Benzathine penicillin (Ref: KDT 6/e p697)
52. Ans. (a) Methicillin resistant Staph aureus (Ref: KDT 6/e p702, 703)
• Staphylococcus aureus develops resistance to methicillin by acquiring altered penicillin binding proteins that have low
affinity. No β-lactam antibiotic is effective against MRSA.
• Clavulanic acid is an inhibitor of β-lactamase. It can restore the sensitivity of penicillins against the organisms who
have developed penicillinases.
53. Ans. (b) It acts by inhibiting bacterial protein synthesis (Ref: KDT 6/e p732)
• Vancomycin is a glycopeptide that acts by inhibiting bacterial cell wall synthesis. It is a bactericidal drug (like other
cell wall synthesis inhibitors).
• It is the drug of choice for MRSA and enterococci resistant to penicillins.
• Nephrotoxicity, ototoxicity and red man syndrome are prominent adverse effects of vancomycin.
54. Ans. (c) It is not susceptible to penicillinases (Ref: KDT 6/e p732)
• Vancomycin is a glycopeptide bactericidal antibiotic that is administered by parenteral route.
• It is penicillinase resistant, thus can be used in MRSA infections.
• It is also used for the treatment of pseudomembranous colitis.
• Vancomycin is ineffective against pseudomonas.
55. Ans. (c) Piperacillin (Ref: KDT 6/e p702)
• Piperacillin can be combined with beta-lactamase inhibitor, tazobactam.
• Vancomycin is NOT effective against pseudomonas.
• All β-lactams except aztreonam are contra-indicated if severe allergic reaction develops to any β-lactam antibiotic.
56. Ans. (b) Aztreonam (Ref: KDT 6/e p708)
In patient with severe sensitivity to penicillin, all beta lactams except monobactams are contraindicated. Both aztreonam
and imipenem are effective for gram negative infections but because imipenem causes seizures as serious adverse effect,
aztreonam is preferred in such a patient.
57. Ans. (d) Given twice daily orally (Ref: KDT 6/e p707)
• Cefepime is a a 4th generation cephalosporin.
• Due to high potency and extended spectrum, it is effective in many serious infections like hospital acquired
pneumonia, febrile neutropenia, bacteremia, septicemia etc.
• All β-lactam antibiotics act by inhibiting the enzyme transpeptidase.
• Cefepime is given by i.v. route as it is not effctive orally.
58. Ans. (a) Cephalexin (Ref: KDT 6/e p704-705; Goodman & Gilman 10/e p1209)
Cephalexin is an orally effective first generation cephalosporin active against gram positive but not against gram negative
organisms like pseudomonas.
59. Ans. (a) Imipenem (Ref: KDT 6/e p708)
60. Ans. (c) Ceftazidime (Ref: KDT 6/e p706)
61. Ans. (b) Benzathine penicillin is short acting penicillin (Ref: KDT 6/e p697, 699, 700)
Benzathine penicillin is the longest acting penicillin.
62. Ans. (a) Inhibition of cell wall synthesis (Ref: KDT 6/e p668)
63. Ans. (a) Effective in pseudomonas infection (Ref: KDT 6/e p702)
• Carbenicillin is a penicillin congener effective against pseudomonas and indole positive proteus which are not
inhibited by penicillin G or ampicillin/amoxicillin.
• It is inactive orally and excreted rapidly in urine. It is sensitive to penicillinase and acid, so administered parenterally
as sodium salt.
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