penicillins 65/66 Flashcards
Penicillin G (Pfizerpen)
natural penicillin
parenteral admin (IV, IM)
only 33% absorbed after oral admin
60% plasma protein bound (ppb)
-active against many G+ and G-aerobic cocci (except strains producing penicillinase); most spirochetes; some G+ aerobic and anaerobic bacilli
-tend to be inactive against G- aerobic and anaerobic bacilli;
-Inactive against Mycoplasma, Rickettsia, fungi, viruses, and mycobacteria.
Penicillin V Potassium (generic)
natural penicillin
oral admin (used for less serious infections, less active than PCN G against most orgs, only for minor infections)
modified side chain (R=phenoxymethyl) more stable in stomach acid
oral dose gives plasma levels 2-5x higher then PCN G
50-70% ppb
Penicillin G Procaine (Wycillin)
natural penicillin
- used for S. pyogenes infections
- limited use for uncomplicated pneumococcal pneumonia or gonorrhea due to resistance
- injection can produce procaine reactions (bad taste, dizziness, palpitations, auditory and visual disturbances)
Penicillin G Benzathine (Bicillin L‐A, Permapen)
natural penicillin
- strep pharyngitis (1 dose vs 10 days PCN V)
- prophylaxis for RF from GAS (shot every 3-4 wks)
- syphilis
can last 26 days!
Penicillin G Benzathine + Penicillin G Procaine (Bicillin C‐R)
natural penicillin
natural penicillins are dispensed as ??
UNITS
others dispensed by weight
Methicillin
Penicillinase Resistant Penicillin ‐ Anti‐staphylococcal Penicillin
highly bound to plasma proteins (may result in clinical failure)
not used in US anymore
SE: intersitial nephritis
MRSA: usually also resist. to PCNs, ceph, amino glycosides, macrolides
40% ppb
Nafcillin
Penicillinase Resistant Penicillin ‐ Anti‐staphylococcal Penicillin
highly bound to plasma proteins (90% ppb!-may result in clinical failure)
-penetrates CNS, may be used for Staph meningitis
IV admin, inactivated in the acidic gastric environment and shows irregular oral absorption with or without meal
-excreted by liver
most resistant to
Staphylococcal B lactamases
eliminated by biliary excretion, don’t need to adjust the dose for pts with renal failure
Oxacillin (generic, Bactocil)
Penicillinase Resistant Penicillin ‐ Anti‐staphylococcal Penicillin
highly bound to plasma proteins (may result in clinical failure)
IV admin
excreted by liver
94% bbp!
eliminated by biliary excretion and by kidney, don’t need to adjust the dose for pts with renal failure?
Penicillinase resistants
implies more resistance to b-lactamases
Ampicillin (generic, Principen)
Extended Spectrum Penicillin (Aminopenicillin)
G+ AND G- coverage
can cause non-allergic skin rash
IV, oral absorption (40%, not as good as amoxicillin)
20% ppb
longer 1/2 life than PCN G
doses adjusted for renal failure
Amoxicillin (generic, Amoxil, Trimox)
Extended Spectrum Penicillin (Aminopenicillin)
G+ AND G- coverage
oral, good absorption (95%) in presence or absence of food, therapeutic plasma levels are obtainable with a lower dose
can cause non-allergic skin rash
20% ppb
longer 1/2 life than PCN G
doses adjusted for renal failure
Ticarcillin + Clavulanate potassium (Timentin); Ticarcillin (Ticar)
Antipseudomonal Penicillin (+B-lactamase inhibitors) combo bc of resistance
45% ppb
adjust for renal failure pts
-G- aerobic bacilli and mixed aerobic‐anaerobic infections (intra-abdominal, gene inf.)
(if Bacteroides, Ticar is alternative, metronidazole is preferred)
-pseudomonal infections (septicemia, UTIs) watch out for resistant strains which may arise
-may add an aminoglycoside (e.g. gentamicin)
SE: excess Na+, prolonged bleeding time
Piperacillin + Tazobactam (Zosyn); Piperacillin (Pipracil)
Ureidopenicillin
Antipseudomonal Penicillin (+B-lactamase inhibitors) combo bc of resistance IV *broader spec. and more active against G- bacilli/mixed anaerobic/aerobic infections (Pseudomonas, Kleb) than carbenicillin or ticarcillin
Aztreonam
B-lactam drug (other)
monobactam (monocyclic B-lactam ring- unique!)
poor oral absorption, admin parentally
excreted by kidneys, adjust dose for renal impairment
Imipenem + Cilastatin (Primaxin)
B-lactam drug (other)
carbapenem
broadest spectrum of activity
not absorbed orally
Clavulanic acid
B-lactam drug (other)
B-lactamase inhibitor
not much abx activity (always used in combo), needed to prevent breakdown from bacterial B-lactamase -most active against Amber class A B-lactamases, not good inhibitors of class C (B-lactam ring structure similar to amoxicillin; acts a suicide inhibitor of beta‐lactamase thus preventing the beta‐lactamse from breaking down amoxicillin).
Tazobactam
B-lactam drug (other)
B-lactamase inhibitor
not much abx activity (always used in combo), needed to prevent breakdown from bacterial B-lactamase -most active against Amber class A B-lactamases, not good inhibitors of class C
Amoxicillin + Clavulanic acid (Augmentin)
Combination products containing Beta lactamase inhibitor
good oral absorption
high levels in urine, does not penetrate CNS
excreted in kidney, adjust for renal impairment
Ticarcillin + Clavulanic acid (Timentin)
Combination products containing Beta lactamase inhibitor
Piperacillin + Tazobactam (Zosyn)
Combination products containing Beta lactamase inhibitor
core structure of PCNs
6-aminopenicillanic acid
B-lactam ring, Thiazolidine ring
(need intact rings for function!)
different pharmacokinetic, antibacterial props, different susceptibilities to breakdown based on R group
mechanism of B-lactam abx
bactericidal against bacteria that are actively growing by inhibiting bacterial cell wall synthesis
inhibit transpeptidase (PBP)–>inhibit bac cell wall synthesis–>lysis and killing of bacteria (activate autolysins)
ultimate death: activation of cell‐wall autolytic enzymes called autolysins (murein hydrolases) and bacterial cell lysis.
bacterial cell wall synthesis
net effect of this process is the production of glycan chains (alternating amino sugars; N-acetylglucoasamine and N‐acetylmuramic acid) that are cross‐linked by peptide chains
The final step in the production of the peptidoglycan cell wall is the complete cross‐ linking of the chains. This enzymatic process is accomplished by a transpeptidase enzyme located on the outside of the cell membrane.
B-lactam abx inhibit the ??
how can they do this??
transpeptidase enzyme and the subsequent production of a highly cross‐linked peptidoglycan cell wall
Penicillin covalently binds to the transpeptidase enzyme because there is a structural similarity between the penicillin molecule and the D‐alanyl‐D‐alanine end of the glycopeptide polymer (the normal substrate for the transpeptidase enzyme).
penicillins exert their bactericidal effect only on ??
actively dividing cells that are producing cell wall. Penicillins will have little or no effect on dormant bacteria or on microorganisms that lack cell walls. (not active against mycoplasma)
PCNs: good or bad selectivity??
good! humans do not have cell walls
PCNs are often used in combination with an ?? for a synergistic killing effect. Avoid ??
aminoglycoside antibiotic (e.g. gentamicin) Avoid in vitro mixing of penicillin family members with an aminoglycoside antibiotic in the same solution. (-/+-->deactivation)