Beta Lactam Antibiotics Flashcards
How do beta-lactam antibiotics work?
inhibits cell wall biosynthesis by binding to penicillin binding proteins (PBPs). bactericidal of growing bacteria.
How do bacteria develop resistance to beta lactams?
by synthesizing β-lactamase (penicillinase), an enzyme that breaks down the beta-lactam ring and inactivates the antibiotic.
How do we overcome beta-lactam resistance?
β-lactam antibiotics are often given with β-lactamase inhibitors such as clavulanic acid.
What are the classes of beta-lactam compounds?
Penicillins, Cephalosporins, Beta-Lactamase Inhibitors- combined w/ PCN’s
What are the classifications of penicillins?
Penicillin G (IM or IV, if oral form it’s called penicillin B). Antistaphlococcal PCNs: nafcillin, dicloxacillin, Oxacillin, cloxacillin. Broad Spectrum PCNs: 2nd generation- ampicillin, amoxicillin or 3rd generation carbenicillin, ticarcillin or 4th generation piperacillin
What are the penicillin combos w/beta-lactamase inhibitors?
amoxacillin/potassium clavulanate (Augmentin), ampicillin/sulbactam (unasyn), Ticarcillin/potassium clavulanate (Timentin), Piperacillin & tazobactam sodium (Zosyn)
What are some precautions of PCNs?
should be given on an empty stomach (one hr before eating or 2 hrs after eating), Giving PCNs with probenecid (500mg q 6 hrs) increases blood levels of all PCNs. PCNs can cause encephalopathy, somnolence, stupor, coma, seizures, diarrhea or C.diff
What infections are treated with Penicillin G?
sepsis, pneumonia, pericarditis, endocarditis, meningitis, anthrax
What type of organisms is Penicillin G active against?
Gram-positive cocci (streptococci, staphylococci), Gram-positive rods (Listeria), Gram-negative cocci (Neisseria). Most anaerobes
What is the usual dosage of Penicillin G?
1-24 million units/day divided every 4-6 hours. Erysipelas: IV: 1-2 million units every 4-6 hours x 7-10 days. Neurosyphilis: IV: 18-24 million units/day in divided doses every 4 hours for 10-14 days
What is the activity of antistaphylococcal PCNs (dicloxacillin, oxacilliln, nafcillin)?
used for infection with beta-lactamase-producing staph, also used against PCN susceptible strains strep, & pneumococci. Inactive against Enterococci & methicilliin resistant strains
What are the usual dosages of antistaphylococcal PCNs?
Dicloxacillin 125-500 mg PO q 6h. Oxacillin 250-1000mg IM/IV q4-6h. Nafcillin 0.5-2g IV q4-6h
What are 2nd generation (ampicillin and amoxicillin) PCNs active against?
most E. coli, Proteus mirabilis, Salmonella, Shigella & H. influenzae. Used to treat otitis, sinusitis, lower RTI.
What are the usual dosages of 2nd generation PCNs?
amoxicillin 250-500 mg q8hr (ampicillin q6h). Augmentin (amoxicillin + clavulanic acid) 875mg q12 h (expands coverage to gram +/- and anaerobes)
Why is ampicillin not recommended for mononuclesosis?
A high percentage of patients with infectious mononucleosis have developed rash during therapy
What is the activity of 3rd generation (carbenicillin and ticarcillin) PCNs?
strep, enteric gram-neg bacilli (E. coli, Klebsiella pneumoniae, Enterobacter cloacea, Enterobacter aerogenes and Proteus miriabilis), Pseodomonas and anaerobes.
What is the dosage for 3rd generation (carbenicillin and ticarcillin) PCNs?
ticarcillin IV 3 g q4-6h, 150-200 mg/kd/d in 2-3 doses. available in combo w/ Clavulanate K+ (Temectin)
What is the standard therapy anti-pseudomonal med in hospitals?
3rd generation PCNs (carbenicillin and ticarcillin)
What is Zosyn?
4th generation PCN piperacillin + tazobactam. broad spectrum; used for cellulitis, postpartem endometritis, peritonitis, pneumonia.
What are some complications of PCN therapy?
can cause bleeding problems, interstitial nephritis, neurological complications and seizures, or secondary infections such as vaginal candidiasis
What are the beta-lactamase inhibitors?
clavulanic acid, sulbactam, tazobactam
Describe the use of beta-lactamase inhibitors
only in combination with a PCN. they inactivate aminoglycosides. By themselves don’t have antimicrobial activity.
What is the dosing of Augmentin (amoxacillin-clavulanic acid?
adult: 500-875mg q 12h
ped: 20-40 mg/kg/d q8-12h
What is the dosing of Zosyn (piperacillin-tazobactam)?
adult: 4.5g IV q6-8h
ped: 240 mg/kg/d q8h IV
Describe cephalosporins
as they progress from 1st-4th generation there’s an increase in gram (-) coverage and loss in gram (+). They’re well absorbed from GI tract w/food. 3-10% allergic cross-reactivity w/PCNs.
What is the standard med for a pregnant women w/an UTI?
Keflex (cephalexin)
What are the 1st generation cephalosporins and their activity?
cefadroxil, cephalexin (Keflex), and cefazolin (Ancef). gram positive streptococcus and staphylococcus, good against anaerobic cocci (eg, peptococcus, peptostreptococcus)
What are the usual dosages of 1st gen cephalosporins?
cephalexin (Keflex) 250-500 mg qid used for cellulitis, cefazolin (Ancef) used for surgical prophylaxis 1-2 gm IV
What are the 2nd generation cephalosporins and their activity?
cefuroxime (po 250-500mg bid: IV 1-1.5g q8h), cefoxitin(IV 1-2g q6-8h), cefotetan(IV 1-2g q12h). active against gram-pos cocci, some gram negative coverage Klebsiellae, H. influenzae
What is cefuroxime used to treat?
sinusitis, otitis, RTI, CAP
What is cefoxitin used to treat?
peritonitis & diverticulitis because active against gram-neg rods & Bacteroides
What are the 3rd generation cephalosporins and their activity?
cefotaxime (IV 1-2g q6-12h), ceftazidime (IV 1-2g q8-12h), ceftriaxone (1-4g q24h). gram-neg meningicoccus, citrobacter, beta-lactamase strains of haemophilus and neisseria,
What are 3rd generation cephalosporins used to treat?
ceftriaxone & cefotaxime treat meningitis,
empirical therapy serious infections because effective against PCN-resistant strains pnemonococci, & sepsis. ceftriaxone used to treat gonorhea/Lyme disease
What is the 4th generation cephalosporin and its activity?
cefepime (IV 0.5-2g q12h, peds 75-120mg/kg/d divided 2-3 doses). Gram positive and negative, including pseudomonas, S aureus, S pneumoniae, haemophilus and Neisseria
What is cefepime used to treat?
meningitis, serious infections and sepsis. sometimes use with an aminoglycoside when treating pseudomonas
What is effective therapy for pseudomonas meningitis?
ceftazidime (3rd gen cephalosporin)
What are carbapenems and their activity?
Imipenem/cilastatin (IV 250-500mg q6-8h), meropenem (IV 1-2g q8h). resistant to cleavage (beta-lactamase); gram-pos(including Enterococcus faecallis & listeria), gram-neg (H influenzae, N gonorrhoeae, Enterobacter & Pseudomonus), Anerobes (including Bacteroides)
What are carbapenems used to treat?
meropenem for meningitis, intraabdominal infections, pseudomonus and with or without an aminoglycoside for neutropenic patient
