Penicillins Flashcards

Question

Amoxicillin / Clavulanic Acid

Answer 1

Expanded spectrum includes: • β-lactamase producing Staphylococci (not MRSA, MRSE), • Haemophilus influenzae, Moraxella catarrhalis • Many Enterobacterales (E.coli, Klebsiella pneumoniae, Proteus mirabilis) • Not AmpC β-lactamase producing Enterobacterales or Pseudomonas • Bacteroides spp., including B. fragilis

Answer 2

• Carboxypenicillins (Ticarcillin) ??? (please check, this is crossed - out in the slide) • Ureidopenicillins (Piperacillin)

Answer 3

• Spectrum of activity includes - β-lactamase producing Staphylococci (not MRSA) - Streptococci and Enterococci (comparable to ampicillin/amoxicillin) - Good activity against Pseudomonas aeruginosa * UAH – 84% Susceptible (2019) * Edmonton Community – 94% Susceptible (2019) - H. influenzae, M. catarrhalis - Many Enterobacterales, including ESBL* producing E.coli, Klebsiella - Bacteroides fragilis ``` • Does not improve activity against AmpC producing “SPICE A” organisms - Serratia, Providencia, Indole-positive Proteus (P. vulgaris), Citrobacter, Enterobacter, Acinetobacter ```

Answer 4

• well distributed to most areas • in presence of inflammation - good levels middle ear, pleural, peritoneal, and synovial fluids and adequate CSF levels • in absence of inflammation - levels minimal in CSF, eye, brain, prostate - in CNS – inflammation permits entry and alters anion pump that removes penicillins from CNS (as in meningitis) • Protein binding variable - 17% ampicillin - 94% cloxacillin

Answer 5

• Most excreted intact by kidneys by glomerular filtration and renal tubular secretion • Most have high levels in urine, even with moderate renal failure - but once CrCl < 10 mL/min, urine levels not > blood levels • minor degree metabolism in all ``` • some degree of biliary excretion in all, particularly with antistaphylococcal penicillins (e.g., cloxacillin) ``` • t 1/2 vary 30 - 72 min

Answer 6

see slide 37 pen G, Cloxaxillin, ampicillin Pen V better abs on empty stomach but not as important

Answer 7

• ↓ renal function elderly, neonates, and those with compromised renal function • CrCl < 10 ml/min - slight reduction in most - No change for cloxacillin (hepatic and biliary compensation)

Answer 8

• Main adverse effects of penicillins are hypersensitivity reactions ranging from rash to anaphylaxis • 1-10% of patients receiving penicillin will have an adverse reaction, including allergy • Estimated as many as 1/2 of all allergic reactions occurring in hospital are due to β-lactam antibacterials ( Bugs & Drugs ) • 0.01-0.02% treated with parenteral penicillin have life threatening anaphylactic reactions, with a fatality rate of 0.0015-0.02% ( Bugs & Drugs )

Answer 9

``` • Myoclonic Seizures (Rare) - More likely if penicillin given - Large Doses - (usual adult dose penicillin ranges from 500,000U bid – 2 million units q2h) ``` • Or penicillin given in patients with renal failure without dosage adjustment - (direct application to cortex → seizures) - (instillation into ventricles at the time of shunt placement no seizures)

Answer 10

• Interstitial Nephritis <1% (Type III Reaction) - Rare - ranges from allergic angiitis to interstitial nephritis - fever, rash, eosinophilia, proteinuria, hematuria - may progress to anuria and renal failure - Usually only after long term, high dose therapy - most common with methicillin, but may occur with any penicillin - most return to normal after discontinue drug

Answer 11

• Neutropenia (1- 4%) (Type II reaction) - may occur with all penicillins - more often with large doses - WBC count returns to normal after discontinue drug - lower dose may sometimes be tolerated - In patients with previous hemolytic reaction to pencillin, re-administration of pencillin may result in a rapid hemolytic response resulting in death • Coombs positive hemolytic anemia - Rare - Type II reaction * penicillin binds to RBC * antibody forms * Complement is fixed and Membrane Attack Complex (MAC) forms with destruction of RBC

Answer 12

• Hepatic - ↑ alkaline phosphatase, ↑ AST - most often in past with oxacillin, carbenicillin (which we don’t use clinically now) - hepatic injury uncommon (1- 4%) - enzymes return to normal when discontinue drug

Answer 13

• Allopurinol and Ampicillin - increased incidence of rash ( up to 14 - 22.4%) * Oral Contraceptives * Aminoglycosides (synergy; in vitro inactivation) ``` Prolong half life of Avoid giving together Separate by hours Ynergistic Inactivate each other in vitro ``` • Probenecid (reduced excretion/increased levels) Prolonged dosing intervals, purposely given with beta lactams

Penicillins Flashcards

(37 cards)