Inhibitors of Cell Wall Synthesis - Penicillins

Question 1

5 classes of penicillins (Beta-lactams)

Answer 1

natural; penicillinase resistant (antistaphylococcal); extended spectrum; anti-pseudomonal; combination products with beta-lactimase inhibitors

Question 2

natural penicillins and their dosage forms

Answer 2

Penicillin G - IV, IM,
Benzathine Penicillin - IM
Procain Penicillin G - IM
Penicillin V - oral

Question 3

natural penicillins are effective against

Answer 3

highest activity against gram positive; some gram negative and some anaerobic; no antipseudomonal activity

N. gonorrhoeae; S. pneumoniae; Treponema…

Question 4

distribution, metabolism, and elimination of natural penicillins

Answer 4

eliminated by active transport in the kidney

poor CNS penetration

Question 5

mechanism of action of penicillins

Answer 5

bactericidal - only if bacteria are actively growing
inhibit the final stage (cross-linking) of bacterial cell wall synthesis by binding to specific penicillin-binding proteins (PBP), leading to cell lysis

Question 6

penicillinase resistant penicillins and their dosage forms

Answer 6

Nafcillin - IV, IM
Oxacillin - IV, IM, oral
Dicloxacillin - oral
methicillin - testing only

Question 7

penicillinase resistant penicillins are effective against

Answer 7

DOC Beta-lactamase positive Staph. aureus (MSSA)

Gram-positive coverage; some gram negative and anaerobic coverage

Question 8

distribution, metabolism, and elimination of penicillinase resistant penicillins

Answer 8

hepatic metabolism

renal excretion

Question 9

extended spectrum penicillins and their dosage forms

Answer 9

Ampicillin - oral

Amoxicillin - oral

Question 10

ampicillin rash?

Answer 10

not a hypersensitivity reaction in children or patients with EBV

Question 11

extended spectrum penicillins are effective against

Answer 11

Listeria species, E. coli, Salmonella

Gram-positive coverage; extended gram negative coverage, no antipsudomonal activity, susceptible to beta-lactamase

Question 12

distribution, metabolism, and elimination of extended spectrum penicillins

Answer 12

urinary excretion

Question 13

antipseudomonal penicillins and their dosage forms

Answer 13

Piperacillin - parenteral
Ticarcillin - parenteral
Mezlocillin - parenteral
Carbenicillin - parenteral

Question 14

antipseudomonal penicillins are effective against

Answer 14

Pseudomonas aeruginosa (in combination with aminoglycosides)

bacteria covered under the extended spectrum penicillins plus additional enteric gram negative bacilli
Proteus, Enterobacter, Serratia…

Question 15

distribution, metabolism, and elimination of antipseudomonal penicillins

Answer 15

renal excretion

Question 16

combination products with beta-lactamase inhibitors and their dosage forms

Answer 16

ampicillin + sulbactam (Unasyn) - IV, IM
amoxicillin + clavulanic acid (Augmentin) - oral
piperacillin + tazobactam (Zosyn) - IV
ticarcillin + clavulanic acid (Timentin)- IV

Question 17

mechanisms of bacterial resistance to penecillins

Answer 17

Inactivation of penicillin by beta-lactamase.
Decreased permeability of cell wall.
Alteration in PBP to prevent penicillin binding (MRSA).
Deactivation of autolytic enzyms (autolysins) so bacterial cell isn’t growing.
Lack of cell wall or wall not peptidoglycan based.

Question 18

toxicity of penicillins

Answer 18

Greatest potential for allergic reactions (cross-allergic and cross-sensitizing for all penicillins).
Potential for electrolyte imbalances, GI disturbances, and development of super-infections.